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@@ -63,6 +63,15 @@ The library uses the following mapping from JSON values types to BJData types ac
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- strings with more than 18446744073709551615 bytes, i.e., 2<sup>64</sup>-1 bytes (theoretical)
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!!! warning "UTF-8 validation of string values and object keys"
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BJData strings must use UTF-8 encoding. By default (the [`error_handler`](../../api/basic_json/to_bjdata.md)
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parameter left at `keep`), `to_bjdata()` writes the bytes of string values and object keys unchanged, even if they
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are not valid UTF-8. With `error_handler_t::strict`, it throws
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[`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) for ill-formed UTF-8 instead;
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`replace`/`ignore` sanitize the string. [`JSON_STRICT_BINARY_UTF8`](../../api/macros/json_strict_binary_utf8.md)
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makes `strict` the default.
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!!! info "Unused BJData markers"
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The following markers are not used in the conversion:
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@@ -208,6 +217,19 @@ The library maps BJData types to JSON value types as follows:
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The mapping is **complete** in the sense that any BJData value can be converted to a JSON value.
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!!! warning "Ill-formed UTF-8 in string values and object keys"
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BJData strings must use UTF-8 encoding, but checking it on read is opt-in: with the
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[`error_handler`](../../api/basic_json/from_bjdata.md) parameter left at `keep` (the default), `from_bjdata()`
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accepts a string value or object key whose bytes are not valid UTF-8 and hands them back unchanged. Passing
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`error_handler_t::strict` makes `from_bjdata()` check and throw
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[`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) for ill-formed UTF-8, and
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`replace`/`ignore` sanitize the string instead of keeping it. However,
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[`dump()`](../../api/basic_json/dump.md) still requires valid UTF-8 and throws
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[`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) for a value read with the default
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`keep` handler, unless an error handler is passed that replaces or ignores the ill-formed bytes. `to_bjdata()`'s
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own `error_handler` parameter defaults to `keep` (see above), so such a value is written back unchanged.
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!!! info "Round trips"
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A value returned by [`from_bjdata`](../../api/basic_json/from_bjdata.md) can be serialized with
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@@ -1,4 +1,4 @@
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/bjdata/" rel="canonical"><link href=../ rel=prev><link href=../bon8/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>BJData - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#bjdata class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> BJData </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <div class=md-searcLine truncated
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/bjdata/" rel="canonical"><link href=../ rel=prev><link href=../bon8/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>BJData - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#bjdata class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> BJData </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <div class=md-searcLine truncated
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<span class=w> </span><span class=nt>"_ArrayType_"</span><span class=p>:</span><span class=w> </span><span class=s2>"uint8"</span><span class=p>,</span>
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<span class=w> </span><span class=nt>"_ArraySize_"</span><span class=p>:</span><span class=w> </span><span class=p>[</span><span class=mi>2</span><span class=p>,</span><span class=mi>3</span><span class=p>],</span>
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<span class=w> </span><span class=nt>"_ArrayData_"</span><span class=p>:</span><span class=w> </span><span class=p>[</span><span class=mi>1</span><span class=p>,</span><span class=mi>2</span><span class=p>,</span><span class=mi>3</span><span class=p>,</span><span class=mi>4</span><span class=p>,</span><span class=mi>5</span><span class=p>,</span><span class=mi>6</span><span class=p>]</span>
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@@ -71,7 +71,7 @@
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<span class=p>[</span><span class=n>i1i2i3i4i5i6i7i8</span><span class=p>]</span>
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<span class=p>[</span><span class=err>#</span><span class=n>i8i1i2i3i4i5i6i7i8</span>
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<span class=p>[</span><span class=n>$i</span><span class=err>#</span><span class=n>i812345678</span>
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</code></pre></div> </details> <h2 id=deserialization>Deserialization<a class=headerlink href=#deserialization title="Permanent link">¶</a></h2> <p>The library maps <abbr title="Binary JData">BJData</abbr> types to <abbr title="JavaScript Object Notation">JSON</abbr> value types as follows:</p> <table> <thead> <tr> <th><abbr title="Binary JData">BJData</abbr> type</th> <th><abbr title="JavaScript Object Notation">JSON</abbr> value type</th> <th>marker</th> </tr> </thead> <tbody> <tr> <td>no-op</td> <td><em>no value, next value is read</em></td> <td><code>N</code></td> </tr> <tr> <td>null</td> <td><code>null</code></td> <td><code>Z</code></td> </tr> <tr> <td>false</td> <td><code>false</code></td> <td><code>F</code></td> </tr> <tr> <td>true</td> <td><code>true</code></td> <td><code>T</code></td> </tr> <tr> <td>float16</td> <td>number_float</td> <td><code>h</code></td> </tr> <tr> <td>float32</td> <td>number_float</td> <td><code>d</code></td> </tr> <tr> <td>float64</td> <td>number_float</td> <td><code>D</code></td> </tr> <tr> <td>uint8</td> <td>number_unsigned</td> <td><code>U</code></td> </tr> <tr> <td>int8</td> <td>number_integer</td> <td><code>i</code></td> </tr> <tr> <td>uint16</td> <td>number_unsigned</td> <td><code>u</code></td> </tr> <tr> <td>int16</td> <td>number_integer</td> <td><code>I</code></td> </tr> <tr> <td>uint32</td> <td>number_unsigned</td> <td><code>m</code></td> </tr> <tr> <td>int32</td> <td>number_integer</td> <td><code>l</code></td> </tr> <tr> <td>uint64</td> <td>number_unsigned</td> <td><code>M</code></td> </tr> <tr> <td>int64</td> <td>number_integer</td> <td><code>L</code></td> </tr> <tr> <td>byte</td> <td>number_unsigned</td> <td><code>B</code></td> </tr> <tr> <td>string</td> <td>string</td> <td><code>S</code></td> </tr> <tr> <td>char</td> <td>string</td> <td><code>C</code></td> </tr> <tr> <td>array</td> <td>array (optimized values are supported)</td> <td><code>[</code></td> </tr> <tr> <td>ND-array</td> <td>object (in JData annotated array format)</td> <td><code>[$.#[.</code></td> </tr> <tr> <td>object</td> <td>object (optimized values are supported)</td> <td><code>{</code></td> </tr> <tr> <td>binary</td> <td>binary (strongly-typed byte array)</td> <td><code>[$B</code></td> </tr> </tbody> </table> <div class="admonition success"> <p class=admonition-title>Complete mapping</p> <p>The mapping is <strong>complete</strong> in the sense that any <abbr title="Binary JData">BJData</abbr> value can be converted to a <abbr title="JavaScript Object Notation">JSON</abbr> value.</p> </div> <div class="admonition info"> <p class=admonition-title>Round trips</p> <p>A value returned by <a href=../../../api/basic_json/from_bjdata/ ><code>from_bjdata</code></a> can be serialized with <a href=../../../api/basic_json/to_bjdata/ ><code>to_bjdata</code></a> using any combination of options and parsed back into an equal value, and serializing that value again with the same options produces the same bytes. The exception is binary values: they are only written as an optimized binary array (<code>[$B</code>) if Draft 3 is enabled and both <code>use_size</code> and <code>use_type</code> are set. Otherwise, they are written as arrays of integers and parsed back as such (see the notes on binary values above), and serializing such an array again may choose different, but equally valid, type markers. The bytes can then differ, but parsing them again yields the same value.</p> </div> <details class=example> <summary>Example: deserialize a <abbr title="JavaScript Object Notation">JSON</abbr> value from <abbr title="Binary JData">BJData</abbr></summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
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||||
</code></pre></div> </details> <h2 id=deserialization>Deserialization<a class=headerlink href=#deserialization title="Permanent link">¶</a></h2> <p>The library maps <abbr title="Binary JData">BJData</abbr> types to <abbr title="JavaScript Object Notation">JSON</abbr> value types as follows:</p> <table> <thead> <tr> <th><abbr title="Binary JData">BJData</abbr> type</th> <th><abbr title="JavaScript Object Notation">JSON</abbr> value type</th> <th>marker</th> </tr> </thead> <tbody> <tr> <td>no-op</td> <td><em>no value, next value is read</em></td> <td><code>N</code></td> </tr> <tr> <td>null</td> <td><code>null</code></td> <td><code>Z</code></td> </tr> <tr> <td>false</td> <td><code>false</code></td> <td><code>F</code></td> </tr> <tr> <td>true</td> <td><code>true</code></td> <td><code>T</code></td> </tr> <tr> <td>float16</td> <td>number_float</td> <td><code>h</code></td> </tr> <tr> <td>float32</td> <td>number_float</td> <td><code>d</code></td> </tr> <tr> <td>float64</td> <td>number_float</td> <td><code>D</code></td> </tr> <tr> <td>uint8</td> <td>number_unsigned</td> <td><code>U</code></td> </tr> <tr> <td>int8</td> <td>number_integer</td> <td><code>i</code></td> </tr> <tr> <td>uint16</td> <td>number_unsigned</td> <td><code>u</code></td> </tr> <tr> <td>int16</td> <td>number_integer</td> <td><code>I</code></td> </tr> <tr> <td>uint32</td> <td>number_unsigned</td> <td><code>m</code></td> </tr> <tr> <td>int32</td> <td>number_integer</td> <td><code>l</code></td> </tr> <tr> <td>uint64</td> <td>number_unsigned</td> <td><code>M</code></td> </tr> <tr> <td>int64</td> <td>number_integer</td> <td><code>L</code></td> </tr> <tr> <td>byte</td> <td>number_unsigned</td> <td><code>B</code></td> </tr> <tr> <td>string</td> <td>string</td> <td><code>S</code></td> </tr> <tr> <td>char</td> <td>string</td> <td><code>C</code></td> </tr> <tr> <td>array</td> <td>array (optimized values are supported)</td> <td><code>[</code></td> </tr> <tr> <td>ND-array</td> <td>object (in JData annotated array format)</td> <td><code>[$.#[.</code></td> </tr> <tr> <td>object</td> <td>object (optimized values are supported)</td> <td><code>{</code></td> </tr> <tr> <td>binary</td> <td>binary (strongly-typed byte array)</td> <td><code>[$B</code></td> </tr> </tbody> </table> <div class="admonition success"> <p class=admonition-title>Complete mapping</p> <p>The mapping is <strong>complete</strong> in the sense that any <abbr title="Binary JData">BJData</abbr> value can be converted to a <abbr title="JavaScript Object Notation">JSON</abbr> value.</p> </div> <div class="admonition warning"> <p class=admonition-title>Ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8 in string values and object keys</p> <p><abbr title="Binary JData">BJData</abbr> strings must use <abbr title="Unicode Transformation Format">UTF</abbr>-8 encoding, but checking it on read is opt-in: with the <a href=../../../api/basic_json/from_bjdata/ ><code>error_handler</code></a> parameter left at <code>keep</code> (the default), <code>from_bjdata()</code> accepts a string value or object key whose bytes are not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and hands them back unchanged. Passing <code>error_handler_t::strict</code> makes <code>from_bjdata()</code> check and throw <a href=../../../home/exceptions/#jsonexceptionparse_error113><code>parse_error.113</code></a> for ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8, and <code>replace</code>/<code>ignore</code> sanitize the string instead of keeping it. However, <a href=../../../api/basic_json/dump/ ><code>dump()</code></a> still requires valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and throws <a href=../../../home/exceptions/#jsonexceptiontype_error316><code>type_error.316</code></a> for a value read with the default <code>keep</code> handler, unless an error handler is passed that replaces or ignores the ill-formed bytes. <code>to_bjdata()</code>'s own <code>error_handler</code> parameter defaults to <code>keep</code> (see above), so such a value is written back unchanged.</p> </div> <div class="admonition info"> <p class=admonition-title>Round trips</p> <p>A value returned by <a href=../../../api/basic_json/from_bjdata/ ><code>from_bjdata</code></a> can be serialized with <a href=../../../api/basic_json/to_bjdata/ ><code>to_bjdata</code></a> using any combination of options and parsed back into an equal value, and serializing that value again with the same options produces the same bytes. The exception is binary values: they are only written as an optimized binary array (<code>[$B</code>) if Draft 3 is enabled and both <code>use_size</code> and <code>use_type</code> are set. Otherwise, they are written as arrays of integers and parsed back as such (see the notes on binary values above), and serializing such an array again may choose different, but equally valid, type markers. The bytes can then differ, but parsing them again yields the same value.</p> </div> <detLine truncated
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><iomanip></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span>
|
||||
|
||||
@@ -95,4 +95,4 @@
|
||||
<span class=w> </span><span class=nt>"compact"</span><span class=p>:</span><span class=w> </span><span class=kc>true</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=nt>"schema"</span><span class=p>:</span><span class=w> </span><span class=mi>0</span>
|
||||
<span class=p>}</span>
|
||||
</code></pre></div> </details> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 2, 2026 09:32:15 UTC">October 2, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - 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|
||||
</code></pre></div> </details> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 4, 2026 10:13:49 UTC">October 4, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - 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|
||||
@@ -54,6 +54,10 @@ The following values can **not** be converted to a BJData value:
|
||||
|
||||
- strings with more than 18446744073709551615 bytes, i.e., 264-1 bytes (theoretical)
|
||||
|
||||
UTF-8 validation of string values and object keys
|
||||
|
||||
BJData strings must use UTF-8 encoding. By default (the [`error_handler`](https://json.nlohmann.me/api/basic_json/to_bjdata/index.md) parameter left at `keep`), `to_bjdata()` writes the bytes of string values and object keys unchanged, even if they are not valid UTF-8. With `error_handler_t::strict`, it throws [`type_error.316`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) for ill-formed UTF-8 instead; `replace`/`ignore` sanitize the string. [`JSON_STRICT_BINARY_UTF8`](https://json.nlohmann.me/api/macros/json_strict_binary_utf8/index.md) makes `strict` the default.
|
||||
|
||||
Unused BJData markers
|
||||
|
||||
The following markers are not used in the conversion:
|
||||
@@ -230,6 +234,10 @@ Complete mapping
|
||||
|
||||
The mapping is **complete** in the sense that any BJData value can be converted to a JSON value.
|
||||
|
||||
Ill-formed UTF-8 in string values and object keys
|
||||
|
||||
BJData strings must use UTF-8 encoding, but checking it on read is opt-in: with the [`error_handler`](https://json.nlohmann.me/api/basic_json/from_bjdata/index.md) parameter left at `keep` (the default), `from_bjdata()` accepts a string value or object key whose bytes are not valid UTF-8 and hands them back unchanged. Passing `error_handler_t::strict` makes `from_bjdata()` check and throw [`parse_error.113`](https://json.nlohmann.me/home/exceptions/#jsonexceptionparse_error113) for ill-formed UTF-8, and `replace`/`ignore` sanitize the string instead of keeping it. However, [`dump()`](https://json.nlohmann.me/api/basic_json/dump/index.md) still requires valid UTF-8 and throws [`type_error.316`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) for a value read with the default `keep` handler, unless an error handler is passed that replaces or ignores the ill-formed bytes. `to_bjdata()`'s own `error_handler` parameter defaults to `keep` (see above), so such a value is written back unchanged.
|
||||
|
||||
Round trips
|
||||
|
||||
A value returned by [`from_bjdata`](https://json.nlohmann.me/api/basic_json/from_bjdata/index.md) can be serialized with [`to_bjdata`](https://json.nlohmann.me/api/basic_json/to_bjdata/index.md) using any combination of options and parsed back into an equal value, and serializing that value again with the same options produces the same bytes. The exception is binary values: they are only written as an optimized binary array (`[$B`) if Draft 3 is enabled and both `use_size` and `use_type` are set. Otherwise, they are written as arrays of integers and parsed back as such (see the notes on binary values above), and serializing such an array again may choose different, but equally valid, type markers. The bytes can then differ, but parsing them again yields the same value.
|
||||
|
||||
@@ -1,4 +1,4 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/bon8/" rel="canonical"><link href=../bjdata/ rel=prev><link href=../bson/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>BON8 - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#bon8 class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> BON8 </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <div class=md-searchLine truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/bon8/" rel="canonical"><link href=../bjdata/ rel=prev><link href=../bson/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>BON8 - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#bon8 class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> BON8 </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <div class=md-searchLine truncated
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><iomanip></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span>
|
||||
|
||||
|
||||
@@ -109,14 +109,21 @@ The library maps BSON record types to JSON value types as follows:
|
||||
If BSON input must be validated for strict specification compliance, validate it separately before passing it to
|
||||
`from_bson()`.
|
||||
|
||||
!!! warning "UTF-8 validation of string values"
|
||||
!!! warning "Ill-formed UTF-8 in string values"
|
||||
|
||||
The BSON specification requires `string` values (type `0x02`) to be valid UTF-8. This library validates the
|
||||
bytes of every such string at decode time and rejects ill-formed UTF-8 with a
|
||||
[`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with `allow_exceptions`
|
||||
set to `false`, a discarded value), rather than only failing later when the resulting value is dumped. Element
|
||||
(key) names and `binary` values (type `0x05`) are unaffected and are never validated, since they are read
|
||||
byte-by-byte as a C string, or are not required to hold text, respectively.
|
||||
The BSON specification requires `string` values (type `0x02`) to be valid UTF-8, but this is not required of a
|
||||
decoder, so checking is opt-in: with the [`error_handler`](../../api/basic_json/from_bson.md) parameter left at
|
||||
`keep` (the default), `from_bson()` accepts a `string` value whose bytes are not valid UTF-8 and hands them back
|
||||
unchanged. Passing `error_handler_t::strict` makes `from_bson()` check and throw
|
||||
[`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) for ill-formed UTF-8, and
|
||||
`replace`/`ignore` sanitize the string instead of keeping it. However, [`dump()`](../../api/basic_json/dump.md)
|
||||
still requires valid UTF-8 and throws [`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) for a
|
||||
value read with the default `keep` handler, unless an error handler is passed that replaces or ignores the
|
||||
ill-formed bytes. `to_bson()`'s own `error_handler` parameter defaults to `keep`, so such a string value or element
|
||||
(key) name is written unchanged; with `strict` (the default if
|
||||
[`JSON_STRICT_BINARY_UTF8`](../../api/macros/json_strict_binary_utf8.md) is enabled), it throws the same exception
|
||||
instead. Element (key) names are never validated on read, since they are read byte-by-byte as a C string. `binary`
|
||||
values (type `0x05`) are unaffected, since they are not required to hold text.
|
||||
|
||||
??? example "Example: deserialize a JSON value from BSON"
|
||||
|
||||
|
||||
@@ -1,4 +1,4 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/bson/" rel="canonical"><link href=../bon8/ rel=prev><link href=../cbor/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>BSON - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#bson class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> BSON </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <div class=md-search dLine truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/bson/" rel="canonical"><link href=../bon8/ rel=prev><link href=../cbor/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>BSON - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#bson class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> BSON </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <div class=md-search dLine truncated
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<span class=cp>#include</span><span class=w> </span><span class=cpf><iomanip></span>
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<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span>
|
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@@ -21,7 +21,7 @@
|
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<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span>
|
||||
<span class=p>}</span>
|
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</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=mh>0x1b</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span><span class=mh>0x08</span><span class=w> </span><span class=mh>0x63</span><span class=w> </span><span class=mh>0x6f</span><span class=w> </span><span class=mh>0x6d</span><span class=w> </span><span class=mh>0x70</span><span class=w> </span><span class=mh>0x61</span><span class=w> </span><span class=mh>0x63</span><span class=w> </span><span class=mh>0x74</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span><span class=mh>0x01</span><span class=w> </span><span class=mh>0x10</span><span class=w> </span><span class=mh>0x73</span><span class=w> </span><span class=mh>0x63</span><span class=w> </span><span class=mh>0x68</span><span class=w> </span><span class=mh>0x65</span><span class=w> </span><span class=mh>0x6d</span><span class=w> </span><span class=mh>0x61</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span>
|
||||
</code></pre></div> </details> <h2 id=deserialization>Deserialization<a class=headerlink href=#deserialization title="Permanent link">¶</a></h2> <p>The library maps <abbr title="Binary JSON">BSON</abbr> record types to <abbr title="JavaScript Object Notation">JSON</abbr> value types as follows:</p> <table> <thead> <tr> <th><abbr title="Binary JSON">BSON</abbr> type</th> <th><abbr title="Binary JSON">BSON</abbr> marker byte</th> <th><abbr title="JavaScript Object Notation">JSON</abbr> value type</th> </tr> </thead> <tbody> <tr> <td>double</td> <td>0x01</td> <td>number_float</td> </tr> <tr> <td>string</td> <td>0x02</td> <td>string</td> </tr> <tr> <td>document</td> <td>0x03</td> <td>object</td> </tr> <tr> <td>array</td> <td>0x04</td> <td>array</td> </tr> <tr> <td>binary</td> <td>0x05</td> <td>binary</td> </tr> <tr> <td>undefined</td> <td>0x06</td> <td><em>unsupported</em></td> </tr> <tr> <td>ObjectId</td> <td>0x07</td> <td><em>unsupported</em></td> </tr> <tr> <td>boolean</td> <td>0x08</td> <td>boolean</td> </tr> <tr> <td>UTC Date-Time</td> <td>0x09</td> <td><em>unsupported</em></td> </tr> <tr> <td>null</td> <td>0x0A</td> <td>null</td> </tr> <tr> <td>Regular Expr.</td> <td>0x0B</td> <td><em>unsupported</em></td> </tr> <tr> <td>DB Pointer</td> <td>0x0C</td> <td><em>unsupported</em></td> </tr> <tr> <td>JavaScript Code</td> <td>0x0D</td> <td><em>unsupported</em></td> </tr> <tr> <td>Symbol</td> <td>0x0E</td> <td><em>unsupported</em></td> </tr> <tr> <td>JavaScript Code w/ scope</td> <td>0x0F</td> <td><em>unsupported</em></td> </tr> <tr> <td>int32</td> <td>0x10</td> <td>number_integer</td> </tr> <tr> <td>uint64(Timestamp)</td> <td>0x11</td> <td>number_unsigned</td> </tr> <tr> <td>int64</td> <td>0x12</td> <td>number_integer</td> </tr> <tr> <td>128-bit decimal float</td> <td>0x13</td> <td><em>unsupported</em></td> </tr> <tr> <td>Max Key</td> <td>0x7F</td> <td><em>unsupported</em></td> </tr> <tr> <td>Min Key</td> <td>0xFF</td> <td><em>unsupported</em></td> </tr> </tbody> </table> <div class="admonition warning"> <p class=admonition-title>Incomplete mapping</p> <p>The mapping is <strong>incomplete</strong>. The unsupported mappings are indicated in the table above.</p> </div> <div class="admonition note"> <p class=admonition-title>Handling of <abbr title="Binary JSON">BSON</abbr> type 0x11</p> <p>This library deserializes <abbr title="Binary JSON">BSON</abbr> type <code>0x11</code> (Timestamp) as a <code>number_unsigned</code> value. The 64-bit value is preserved, but the Timestamp type information is not.</p> </div> <div class="admonition warning"> <p class=admonition-title>Lenient <abbr title="Binary JSON">BSON</abbr> input handling</p> <p>The <abbr title="Binary JSON">BSON</abbr> reader is lenient in a few areas where the <abbr title="Binary JSON">BSON</abbr> specification is more restrictive:</p> <ul> <li>array element keys are not checked against the required decimal sequence (<code>0</code>, <code>1</code>, <code>2</code>, ...),</li> <li>any non-zero byte is accepted as <code>true</code> for the boolean type, and</li> <li>the payload for binary subtype <code>0x02</code> is returned as-is, including its inner length prefix.</li> </ul> <p>If <abbr title="Binary JSON">BSON</abbr> input must be validated for strict specification compliance, validate it separately before passing it to <code>from_bson()</code>.</p> </div> <div class="admonition warning"> <p class=admonition-title><abbr title="Unicode Transformation Format">UTF</abbr>-8 validation of string values</p> <p>The <abbr title="Binary JSON">BSON</abbr> specification requires <code>string</code> values (type <code>0x02</code>) to be valid <abbr title="Unicode Transformation Format">UTF</abbr>-8. This library validates the bytes of every such string at decode time and rejects ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8 with a <a href=../../../home/exceptions/#jsonexceptionparse_error113><code>parse_error.113</code></a> exception (or, with <code>allow_exceptions</code> set to <code>false</code>, a discarded value), rather than only failing later when the resulting value is dumped. Element (key) names and <code>binary</code> values (type <code>0x05</code>) are unaffected and are never validated, since they are read byte-by-byte as a C string, or are not required to hold text, respectively.</p> </div> <details class=example> <summary>Example: deserialize a <abbr title="JavaScript Object Notation">JSON</abbr> value from <abbr title="Binary JSON">BSON</abbr></summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
</code></pre></div> </details> <h2 id=deserialization>Deserialization<a class=headerlink href=#deserialization title="Permanent link">¶</a></h2> <p>The library maps <abbr title="Binary JSON">BSON</abbr> record types to <abbr title="JavaScript Object Notation">JSON</abbr> value types as follows:</p> <table> <thead> <tr> <th><abbr title="Binary JSON">BSON</abbr> type</th> <th><abbr title="Binary JSON">BSON</abbr> marker byte</th> <th><abbr title="JavaScript Object Notation">JSON</abbr> value type</th> </tr> </thead> <tbody> <tr> <td>double</td> <td>0x01</td> <td>number_float</td> </tr> <tr> <td>string</td> <td>0x02</td> <td>string</td> </tr> <tr> <td>document</td> <td>0x03</td> <td>object</td> </tr> <tr> <td>array</td> <td>0x04</td> <td>array</td> </tr> <tr> <td>binary</td> <td>0x05</td> <td>binary</td> </tr> <tr> <td>undefined</td> <td>0x06</td> <td><em>unsupported</em></td> </tr> <tr> <td>ObjectId</td> <td>0x07</td> <td><em>unsupported</em></td> </tr> <tr> <td>boolean</td> <td>0x08</td> <td>boolean</td> </tr> <tr> <td>UTC Date-Time</td> <td>0x09</td> <td><em>unsupported</em></td> </tr> <tr> <td>null</td> <td>0x0A</td> <td>null</td> </tr> <tr> <td>Regular Expr.</td> <td>0x0B</td> <td><em>unsupported</em></td> </tr> <tr> <td>DB Pointer</td> <td>0x0C</td> <td><em>unsupported</em></td> </tr> <tr> <td>JavaScript Code</td> <td>0x0D</td> <td><em>unsupported</em></td> </tr> <tr> <td>Symbol</td> <td>0x0E</td> <td><em>unsupported</em></td> </tr> <tr> <td>JavaScript Code w/ scope</td> <td>0x0F</td> <td><em>unsupported</em></td> </tr> <tr> <td>int32</td> <td>0x10</td> <td>number_integer</td> </tr> <tr> <td>uint64(Timestamp)</td> <td>0x11</td> <td>number_unsigned</td> </tr> <tr> <td>int64</td> <td>0x12</td> <td>number_integer</td> </tr> <tr> <td>128-bit decimal float</td> <td>0x13</td> <td><em>unsupported</em></td> </tr> <tr> <td>Max Key</td> <td>0x7F</td> <td><em>unsupported</em></td> </tr> <tr> <td>Min Key</td> <td>0xFF</td> <td><em>unsupported</em></td> </tr> </tbody> </table> <div class="admonition warning"> <p class=admonition-title>Incomplete mapping</p> <p>The mapping is <strong>incomplete</strong>. The unsupported mappings are indicated in the table above.</p> </div> <div class="admonition note"> <p class=admonition-title>Handling of <abbr title="Binary JSON">BSON</abbr> type 0x11</p> <p>This library deserializes <abbr title="Binary JSON">BSON</abbr> type <code>0x11</code> (Timestamp) as a <code>number_unsigned</code> value. The 64-bit value is preserved, but the Timestamp type information is not.</p> </div> <div class="admonition warning"> <p class=admonition-title>Lenient <abbr title="Binary JSON">BSON</abbr> input handling</p> <p>The <abbr title="Binary JSON">BSON</abbr> reader is lenient in a few areas where the <abbr title="Binary JSON">BSON</abbr> specification is more restrictive:</p> <ul> <li>array element keys are not checked against the required decimal sequence (<code>0</code>, <code>1</code>, <code>2</code>, ...),</li> <li>any non-zero byte is accepted as <code>true</code> for the boolean type, and</li> <li>the payload for binary subtype <code>0x02</code> is returned as-is, including its inner length prefix.</li> </ul> <p>If <abbr title="Binary JSON">BSON</abbr> input must be validated for strict specification compliance, validate it separately before passing it to <code>from_bson()</code>.</p> </div> <div class="admonition warning"> <p class=admonition-title>Ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8 in string values</p> <p>The <abbr title="Binary JSON">BSON</abbr> specification requires <code>string</code> values (type <code>0x02</code>) to be valid <abbr title="Unicode Transformation Format">UTF</abbr>-8, but this is not required of a decoder, so checking is opt-in: with the <a href=../../../api/basic_json/from_bson/ ><code>error_handler</code></a> parameter left at <code>keep</code> (the default), <code>from_bson()</code> accepts a <code>string</code> value whose bytes are not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and hands them back unchanged. Passing <code>error_handler_t::strict</code> makes <code>from_bson()</code> check and throw <a href=../../../home/exceptions/#jsonexceptionparse_error113><code>parse_error.113</code></a> for ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8, and <code>replace</code>/<code>ignore</code> sanitize the string instead of keeping it. However, <a href=../../../api/basic_json/dump/ ><code>dump()</code></a> still requires valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and throws <a href=../../../home/exceptions/#jsonexceptiontype_error316><code>type_error.316</code></a> for a value read with the default <code>keep</code> handler, unless an error handler is passed that replaces or ignores the ill-formed bytes. <code>to_bson()</code>'s own <code>error_handler</code> parameter defaults to <code>keep</code>, so such a string value or element (key) name is written unchanged; with <Line truncated
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><iomanip></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span>
|
||||
|
||||
@@ -46,4 +46,4 @@
|
||||
<span class=w> </span><span class=nt>"compact"</span><span class=p>:</span><span class=w> </span><span class=kc>true</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=nt>"schema"</span><span class=p>:</span><span class=w> </span><span class=mi>0</span>
|
||||
<span class=p>}</span>
|
||||
</code></pre></div> </details> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 2, 2026 09:32:15 UTC">October 2, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - 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||||
</code></pre></div> </details> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 4, 2026 10:13:49 UTC">October 4, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - 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|
||||
@@ -118,9 +118,9 @@ The BSON reader is lenient in a few areas where the BSON specification is more r
|
||||
|
||||
If BSON input must be validated for strict specification compliance, validate it separately before passing it to `from_bson()`.
|
||||
|
||||
UTF-8 validation of string values
|
||||
Ill-formed UTF-8 in string values
|
||||
|
||||
The BSON specification requires `string` values (type `0x02`) to be valid UTF-8. This library validates the bytes of every such string at decode time and rejects ill-formed UTF-8 with a [`parse_error.113`](https://json.nlohmann.me/home/exceptions/#jsonexceptionparse_error113) exception (or, with `allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting value is dumped. Element (key) names and `binary` values (type `0x05`) are unaffected and are never validated, since they are read byte-by-byte as a C string, or are not required to hold text, respectively.
|
||||
The BSON specification requires `string` values (type `0x02`) to be valid UTF-8, but this is not required of a decoder, so checking is opt-in: with the [`error_handler`](https://json.nlohmann.me/api/basic_json/from_bson/index.md) parameter left at `keep` (the default), `from_bson()` accepts a `string` value whose bytes are not valid UTF-8 and hands them back unchanged. Passing `error_handler_t::strict` makes `from_bson()` check and throw [`parse_error.113`](https://json.nlohmann.me/home/exceptions/#jsonexceptionparse_error113) for ill-formed UTF-8, and `replace`/`ignore` sanitize the string instead of keeping it. However, [`dump()`](https://json.nlohmann.me/api/basic_json/dump/index.md) still requires valid UTF-8 and throws [`type_error.316`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) for a value read with the default `keep` handler, unless an error handler is passed that replaces or ignores the ill-formed bytes. `to_bson()`'s own `error_handler` parameter defaults to `keep`, so such a string value or element (key) name is written unchanged; with `strict` (the default if [`JSON_STRICT_BINARY_UTF8`](https://json.nlohmann.me/api/macros/json_strict_binary_utf8/index.md) is enabled), it throws the same exception instead. Element (key) names are never validated on read, since they are read byte-by-byte as a C string. `binary` values (type `0x05`) are unaffected, since they are not required to hold text.
|
||||
|
||||
Example: deserialize a JSON value from BSON
|
||||
|
||||
|
||||
@@ -189,15 +189,21 @@ The library maps CBOR types to JSON value types as follows:
|
||||
([RFC 8392](https://www.rfc-editor.org/rfc/rfc8392.html)), cannot be read with this library and need a
|
||||
general-purpose CBOR library instead.
|
||||
|
||||
!!! warning "UTF-8 validation of text strings"
|
||||
!!! warning "Ill-formed UTF-8 in text strings"
|
||||
|
||||
[RFC 8949, Section 3.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1) requires CBOR text strings
|
||||
(major type 3) to be valid UTF-8. This library validates the bytes of every text string (object keys included) at
|
||||
decode time and rejects ill-formed UTF-8 with a
|
||||
[`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with
|
||||
`allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting value is
|
||||
dumped. Byte strings (major type 2) are unaffected and are never validated, since they are not required to hold
|
||||
text.
|
||||
[RFC 8949, Section 3.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1) requires CBOR text strings (major
|
||||
type 3) to be valid UTF-8, but leaves it up to the decoder whether to enforce this, so checking is opt-in: with the
|
||||
[`error_handler`](../../api/basic_json/from_cbor.md) parameter left at `keep` (the default), `from_cbor()` accepts a
|
||||
text string (object keys included) whose bytes are not valid UTF-8 and hands them back unchanged. Passing
|
||||
`error_handler_t::strict` makes `from_cbor()` check and throw
|
||||
[`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) for ill-formed UTF-8, and
|
||||
`replace`/`ignore` sanitize the string instead of keeping it. However, [`dump()`](../../api/basic_json/dump.md)
|
||||
still requires valid UTF-8 and throws [`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) for a
|
||||
value read with the default `keep` handler, unless an error handler is passed that replaces or ignores the
|
||||
ill-formed bytes. `to_cbor()`'s own [`error_handler`](../../api/basic_json/to_cbor.md) parameter defaults to `keep`,
|
||||
so such a value is written back unchanged; with `strict` (the default if
|
||||
[`JSON_STRICT_BINARY_UTF8`](../../api/macros/json_strict_binary_utf8.md) is enabled), it throws the same exception
|
||||
instead. Byte strings (major type 2) are unaffected, since they are not required to hold text.
|
||||
|
||||
!!! warning "Tagged items"
|
||||
|
||||
|
||||
@@ -1,4 +1,4 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/cbor/" rel="canonical"><link href=../bson/ rel=prev><link href=../messagepack/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>CBOR - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#cbor class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/cbor/" rel="canonical"><link href=../bson/ rel=prev><link href=../messagepack/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>CBOR - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> CBOR </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette 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6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <div class=md-sLine truncated
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<span class=cp>#include</span><span class=w> </span><span class=cpf><iomanip></span>
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<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span>
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@@ -22,7 +22,7 @@
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<span class=p>}</span>
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</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=mh>0xa2</span><span class=w> </span><span class=mh>0x67</span><span class=w> </span><span class=mh>0x63</span><span class=w> </span><span class=mh>0x6f</span><span class=w> </span><span class=mh>0x6d</span><span class=w> </span><span class=mh>0x70</span><span class=w> </span><span class=mh>0x61</span><span class=w> </span><span class=mh>0x63</span><span class=w> </span><span class=mh>0x74</span><span class=w> </span><span class=mh>0xf5</span><span class=w> </span><span class=mh>0x66</span><span class=w> </span><span class=mh>0x73</span><span class=w> </span><span class=mh>0x63</span><span class=w> </span><span class=mh>0x68</span><span class=w> </span><span class=mh>0x65</span><span class=w> </span><span class=mh>0x6d</span><span class=w> </span><span class=mh>0x61</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span>
|
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</code></pre></div> </details> <h2 id=deserialization>Deserialization<a class=headerlink href=#deserialization title="Permanent link">¶</a></h2> <p>The library maps <abbr title="Concise Binary Object Representation">CBOR</abbr> types to <abbr title="JavaScript Object Notation">JSON</abbr> value types as follows:</p> <table> <thead> <tr> <th><abbr title="Concise Binary Object Representation">CBOR</abbr> type</th> <th><abbr title="JavaScript Object Notation">JSON</abbr> value type</th> <th>first byte</th> </tr> </thead> <tbody> <tr> <td>Integer</td> <td>number_unsigned</td> <td>0x00..0x17</td> </tr> <tr> <td>Unsigned integer</td> <td>number_unsigned</td> <td>0x18</td> </tr> <tr> <td>Unsigned integer</td> <td>number_unsigned</td> <td>0x19</td> </tr> <tr> <td>Unsigned integer</td> <td>number_unsigned</td> <td>0x1A</td> </tr> <tr> <td>Unsigned integer</td> <td>number_unsigned</td> <td>0x1B</td> </tr> <tr> <td>Negative integer</td> <td>number_integer</td> <td>0x20..0x37</td> </tr> <tr> <td>Negative integer</td> <td>number_integer</td> <td>0x38</td> </tr> <tr> <td>Negative integer</td> <td>number_integer</td> <td>0x39</td> </tr> <tr> <td>Negative integer</td> <td>number_integer</td> <td>0x3A</td> </tr> <tr> <td>Negative integer</td> <td>number_integer</td> <td>0x3B</td> </tr> <tr> <td>Byte string</td> <td>binary</td> <td>0x40..0x57</td> </tr> <tr> <td>Byte string</td> <td>binary</td> <td>0x58</td> </tr> <tr> <td>Byte string</td> <td>binary</td> <td>0x59</td> </tr> <tr> <td>Byte string</td> <td>binary</td> <td>0x5A</td> </tr> <tr> <td>Byte string</td> <td>binary</td> <td>0x5B</td> </tr> <tr> <td><abbr title="Unicode Transformation Format">UTF</abbr>-8 string</td> <td>string</td> <td>0x60..0x77</td> </tr> <tr> <td><abbr title="Unicode Transformation Format">UTF</abbr>-8 string</td> <td>string</td> <td>0x78</td> </tr> <tr> <td><abbr title="Unicode Transformation Format">UTF</abbr>-8 string</td> <td>string</td> <td>0x79</td> </tr> <tr> <td><abbr title="Unicode Transformation Format">UTF</abbr>-8 string</td> <td>string</td> <td>0x7A</td> </tr> <tr> <td><abbr title="Unicode Transformation Format">UTF</abbr>-8 string</td> <td>string</td> <td>0x7B</td> </tr> <tr> <td><abbr title="Unicode Transformation Format">UTF</abbr>-8 string</td> <td>string</td> <td>0x7F</td> </tr> <tr> <td>array</td> <td>array</td> <td>0x80..0x97</td> </tr> <tr> <td>array</td> <td>array</td> <td>0x98</td> </tr> <tr> <td>array</td> <td>array</td> <td>0x99</td> </tr> <tr> <td>array</td> <td>array</td> <td>0x9A</td> </tr> <tr> <td>array</td> <td>array</td> <td>0x9B</td> </tr> <tr> <td>array</td> <td>array</td> <td>0x9F</td> </tr> <tr> <td>map</td> <td>object</td> <td>0xA0..0xB7</td> </tr> <tr> <td>map</td> <td>object</td> <td>0xB8</td> </tr> <tr> <td>map</td> <td>object</td> <td>0xB9</td> </tr> <tr> <td>map</td> <td>object</td> <td>0xBA</td> </tr> <tr> <td>map</td> <td>object</td> <td>0xBB</td> </tr> <tr> <td>map</td> <td>object</td> <td>0xBF</td> </tr> <tr> <td>False</td> <td><code>false</code></td> <td>0xF4</td> </tr> <tr> <td>True</td> <td><code>true</code></td> <td>0xF5</td> </tr> <tr> <td>Null</td> <td><code>null</code></td> <td>0xF6</td> </tr> <tr> <td>Half-Precision Float</td> <td>number_float</td> <td>0xF9</td> </tr> <tr> <td>Single-Precision Float</td> <td>number_float</td> <td>0xFA</td> </tr> <tr> <td>Double-Precision Float</td> <td>number_float</td> <td>0xFB</td> </tr> </tbody> </table> <div class="admonition warning"> <p class=admonition-title>Incomplete mapping</p> <p>The mapping is <strong>incomplete</strong> in the sense that not all <abbr title="Concise Binary Object Representation">CBOR</abbr> types can be converted to a <abbr title="JavaScript Object Notation">JSON</abbr> value. The following <abbr title="Concise Binary Object Representation">CBOR</abbr> types are not supported and will yield parse errors:</p> <ul> <li>simple values (0xE0..0xF3, 0xF8)</li> <li>undefined (0xF7)</li> </ul> <p>Tagged items (0xC0..0xDB) are not interpreted either; see the note on tagged items below.</p> </div> <div class="admonition warning"> <p class=admonition-title>Negative integer overflow</p> <p><abbr title="Concise Binary Object Representation">CBOR</abbr> negative integers (major type 1) are decoded as <code>-1 - n</code>. If the encoded magnitude <code>n</code> is too large for the result to fit into <code>number_integer_t</code> (<code>std::int64_t</code> by default), parsing fails with a <a href=../../../home/exceptions/#jsonexceptionparse_error112><code>parse_error.112</code></a> exception rather than overflowing silently.</p> </div> <div class="admonition warning"> <p class=admonition-title>Object keys</p> <p><abbr title="Concise Binary Object Representation">CBOR</abbr> allows map keys of any type, whereas <abbr title="JavaScript Object Notation">JSON</abbr> only allows strings as keys in object values. Therefore, <abbr title="Concise Binary Object Representation">CBOR</abbr> maps with keys other than text strings (major type 3) are rejLine truncated
|
||||
</code></pre></div> <p>This applies to the <a href=../../parsing/sax_interface/ ><abbr title="Simple API for XML">SAX</abbr> interface</a> as well, as the key is read before it is passed on. This is a deliberate restriction of the library's <abbr title="JavaScript Object Notation">JSON</abbr> value model, not an oversight: formats built on <abbr title="Concise Binary Object Representation">CBOR</abbr> maps with integer keys, such as COSE (<a href="https://www.rfc-editor.org/rfc/rfc9052.html"><abbr title="Request for Comments">RFC</abbr> 9052</a>) or CWT (<a href="https://www.rfc-editor.org/rfc/rfc8392.html"><abbr title="Request for Comments">RFC</abbr> 8392</a>), cannot be read with this library and need a general-purpose <abbr title="Concise Binary Object Representation">CBOR</abbr> library instead.</p> </div> <div class="admonition warning"> <p class=admonition-title><abbr title="Unicode Transformation Format">UTF</abbr>-8 validation of text strings</p> <p><a href="https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1"><abbr title="Request for Comments">RFC</abbr> 8949, Section 3.1</a> requires <abbr title="Concise Binary Object Representation">CBOR</abbr> text strings (major type 3) to be valid <abbr title="Unicode Transformation Format">UTF</abbr>-8. This library validates the bytes of every text string (object keys included) at decode time and rejects ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8 with a <a href=../../../home/exceptions/#jsonexceptionparse_error113><code>parse_error.113</code></a> exception (or, with <code>allow_exceptions</code> set to <code>false</code>, a discarded value), rather than only failing later when the resulting value is dumped. Byte strings (major type 2) are unaffected and are never validated, since they are not required to hold text.</p> </div> <div class="admonition warning"> <p class=admonition-title>Tagged items</p> <p>Tagged items (0xC0..0xDB) will throw a parse error by default. They can be ignored by passing <code>cbor_tag_handler_t::ignore</code> to function <code>from_cbor</code>, in which case the tag is skipped and the enclosed data item is parsed on its own. Passing <code>cbor_tag_handler_t::store</code> to function <code>from_cbor</code> stores tagged byte strings (for bytes 0xd8..0xdb) as binary values with the tag as subtype; other tagged values are read as if the tag were ignored. If several tags precede a byte string, only the innermost one is stored. Note that no tag is ever interpreted: for instance, a text string tagged with tag 0 (date/time) stays a string.</p> </div> <details class=example> <summary>Example: deserialize a <abbr title="JavaScript Object Notation">JSON</abbr> value from <abbr title="Concise Binary Object Representation">CBOR</abbr></summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
</code></pre></div> <p>This applies to the <a href=../../parsing/sax_interface/ ><abbr title="Simple API for XML">SAX</abbr> interface</a> as well, as the key is read before it is passed on. This is a deliberate restriction of the library's <abbr title="JavaScript Object Notation">JSON</abbr> value model, not an oversight: formats built on <abbr title="Concise Binary Object Representation">CBOR</abbr> maps with integer keys, such as COSE (<a href="https://www.rfc-editor.org/rfc/rfc9052.html"><abbr title="Request for Comments">RFC</abbr> 9052</a>) or CWT (<a href="https://www.rfc-editor.org/rfc/rfc8392.html"><abbr title="Request for Comments">RFC</abbr> 8392</a>), cannot be read with this library and need a general-purpose <abbr title="Concise Binary Object Representation">CBOR</abbr> library instead.</p> </div> <div class="admonition warning"> <p class=admonition-title>Ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8 in text strings</p> <p><a href="https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1"><abbr title="Request for Comments">RFC</abbr> 8949, Section 3.1</a> requires <abbr title="Concise Binary Object Representation">CBOR</abbr> text strings (major type 3) to be valid <abbr title="Unicode Transformation Format">UTF</abbr>-8, but leaves it up to the decoder whether to enforce this, so checking is opt-in: with the <a href=../../../api/basic_json/from_cbor/ ><code>error_handler</code></a> parameter left at <code>keep</code> (the default), <code>from_cbor()</code> accepts a text string (object keys included) whose bytes are not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and hands them back unchanged. Passing <code>error_handler_t::strict</code> makes <code>from_cbor()</code> check and throw <a href=../../../home/exceptions/#jsonexceptionparse_error113><code>parse_error.113</code></a> for ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8, and <code>replace</code>/<code>ignore</code> sanitize the string instead of keeping it. However, <a href=../../../api/basic_json/dump/ ><code>dump()</code></a> still requires valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and throws <a href=../../../home/exceptions/#jsonexceptiontype_error316><code>type_error.316</code></a> for a value read with the default <code>keep</code> handler, unless an error handler is passed that replaces or ignores the ill-formed bytes. <code>to_cbor()</code>'s own <a href=../../../api/basic_json/to_cbor/ ><code>error_handler</code></a> parameter defaults to <code>keep</code>, so such a value is written back unchanged; with <code>strict</code> (the default if <a href=../../../api/macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled), it throws the same exception instead. Byte strings (major type 2) are unaffected, since they are not required to hold text.</p> </div> <div class="admonition warning"> <p class=admonition-title>Tagged items</p> <p>Tagged items (0xC0..0xDB) will throw a parse error by default. They can be ignored by passing <code>cbor_tag_handler_t::ignore</code> to function <code>from_cbor</code>, in which case the tag is skipped and the enclosed data item is parsed on its own. Passing <code>cbor_tag_handler_t::store</code> to function <code>from_cbor</code> stores tagged byte strings (for bytes 0xd8..0xdb) as binary values with the tag as subtype; other tagged values are read as if the tag were ignored. If several tags precede a byte string, only the innermost one is stored. Note that no tag is ever interpreted: for instance, a text string tagged with tag 0 (date/time) stays a string.</p> </div> <details class=example> <summary>Example: deserialize a <abbr title="JavaScript Object Notation">JSON</abbr> value from <abbr title="Concise Binary Object Representation">CBOR</abbr></summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><iomanip></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span>
|
||||
|
||||
@@ -46,4 +46,4 @@
|
||||
<span class=w> </span><span class=nt>"compact"</span><span class=p>:</span><span class=w> </span><span class=kc>true</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=nt>"schema"</span><span class=p>:</span><span class=w> </span><span class=mi>0</span>
|
||||
<span class=p>}</span>
|
||||
</code></pre></div> </details> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 2, 2026 09:32:15 UTC">October 2, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - 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|
||||
</code></pre></div> </details> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 4, 2026 10:13:49 UTC">October 4, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - 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|
||||
@@ -193,9 +193,9 @@ CBOR allows map keys of any type, whereas JSON only allows strings as keys in ob
|
||||
|
||||
This applies to the [SAX interface](https://json.nlohmann.me/features/parsing/sax_interface/index.md) as well, as the key is read before it is passed on. This is a deliberate restriction of the library's JSON value model, not an oversight: formats built on CBOR maps with integer keys, such as COSE ([RFC 9052](https://www.rfc-editor.org/rfc/rfc9052.html)) or CWT ([RFC 8392](https://www.rfc-editor.org/rfc/rfc8392.html)), cannot be read with this library and need a general-purpose CBOR library instead.
|
||||
|
||||
UTF-8 validation of text strings
|
||||
Ill-formed UTF-8 in text strings
|
||||
|
||||
[RFC 8949, Section 3.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1) requires CBOR text strings (major type 3) to be valid UTF-8. This library validates the bytes of every text string (object keys included) at decode time and rejects ill-formed UTF-8 with a [`parse_error.113`](https://json.nlohmann.me/home/exceptions/#jsonexceptionparse_error113) exception (or, with `allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting value is dumped. Byte strings (major type 2) are unaffected and are never validated, since they are not required to hold text.
|
||||
[RFC 8949, Section 3.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1) requires CBOR text strings (major type 3) to be valid UTF-8, but leaves it up to the decoder whether to enforce this, so checking is opt-in: with the [`error_handler`](https://json.nlohmann.me/api/basic_json/from_cbor/index.md) parameter left at `keep` (the default), `from_cbor()` accepts a text string (object keys included) whose bytes are not valid UTF-8 and hands them back unchanged. Passing `error_handler_t::strict` makes `from_cbor()` check and throw [`parse_error.113`](https://json.nlohmann.me/home/exceptions/#jsonexceptionparse_error113) for ill-formed UTF-8, and `replace`/`ignore` sanitize the string instead of keeping it. However, [`dump()`](https://json.nlohmann.me/api/basic_json/dump/index.md) still requires valid UTF-8 and throws [`type_error.316`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) for a value read with the default `keep` handler, unless an error handler is passed that replaces or ignores the ill-formed bytes. `to_cbor()`'s own [`error_handler`](https://json.nlohmann.me/api/basic_json/to_cbor/index.md) parameter defaults to `keep`, so such a value is written back unchanged; with `strict` (the default if [`JSON_STRICT_BINARY_UTF8`](https://json.nlohmann.me/api/macros/json_strict_binary_utf8/index.md) is enabled), it throws the same exception instead. Byte strings (major type 2) are unaffected, since they are not required to hold text.
|
||||
|
||||
Tagged items
|
||||
|
||||
|
||||
@@ -1 +1 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/" rel="canonical"><link href=../arbitrary_types/ rel=prev><link href=bjdata/ rel=next><link rel=icon href=../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>Binary Formats - JSON for Modern C++</title><link rel=stylesheet href=../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../css/custom.css><script>__md_scope=new 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xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> Binary Formats </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio 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6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <div claLine truncated
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/" rel="canonical"><link href=../arbitrary_types/ rel=prev><link href=bjdata/ rel=next><link rel=icon href=../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>Binary Formats - JSON for Modern C++</title><link rel=stylesheet href=../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../css/custom.css><script>__md_scope=new 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6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <div claLine truncated
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||||
@@ -153,14 +153,23 @@ The library maps MessagePack types to JSON value types as follows:
|
||||
This applies to the [SAX interface](../parsing/sax_interface.md) as well, as the key is read before it is passed
|
||||
on. Such input needs a general-purpose MessagePack library instead.
|
||||
|
||||
!!! warning "UTF-8 validation of string values"
|
||||
!!! warning "Ill-formed UTF-8 in string values"
|
||||
|
||||
The MessagePack specification requires `str` values (`fixstr`, `str 8`, `str 16`, `str 32`) to be valid UTF-8.
|
||||
This library validates the bytes of every such string (object keys included) at decode time and rejects
|
||||
ill-formed UTF-8 with a [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or,
|
||||
with `allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting
|
||||
value is dumped. `bin`/`ext`/`fixext` values are unaffected and are never validated, since they are not required
|
||||
to hold text.
|
||||
The MessagePack specification explicitly allows a `str` value (`fixstr`, `str 8`, `str 16`, `str 32`) to contain
|
||||
a byte sequence that is not valid UTF-8, and expects a deserializer to hand the original bytes back unchanged.
|
||||
This library follows that by default: with its
|
||||
[`error_handler`](../../api/basic_json/from_msgpack.md) parameter left at `keep` (the default),
|
||||
`from_msgpack()` reads `str` bytes (object keys included) as-is, without validating them, so such a value
|
||||
round-trips through `from_msgpack(to_msgpack(j))` byte for byte. Passing `error_handler_t::strict` makes
|
||||
`from_msgpack()` check anyway and throw
|
||||
[`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) for ill-formed UTF-8, and
|
||||
`replace`/`ignore` sanitize the string instead of keeping it. `to_msgpack()` also writes `str` bytes as-is by
|
||||
default, since the specification permits it; its [`error_handler`](../../api/basic_json/to_msgpack.md) parameter
|
||||
can be set to `strict` to throw [`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) instead, or
|
||||
to `replace`/`ignore` to sanitize the string, for instance for a decoder that rejects ill-formed UTF-8. However,
|
||||
[`dump()`](../../api/basic_json/dump.md) still requires valid UTF-8 and throws
|
||||
[`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) for a value read this way with the
|
||||
default `keep` handler, unless an error handler is passed that replaces or ignores the ill-formed bytes.
|
||||
|
||||
??? example "Example: deserialize a JSON value from MessagePack"
|
||||
|
||||
|
||||
@@ -1,4 +1,4 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/messagepack/" rel="canonical"><link href=../cbor/ rel=prev><link href=../ubjson/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>MessagePack - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> <Line truncated
|
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/messagepack/" rel="canonical"><link href=../cbor/ rel=prev><link href=../ubjson/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>MessagePack - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#messagepack class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> MessagePack </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> <Line truncated
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><iomanip></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span>
|
||||
|
||||
@@ -22,7 +22,7 @@
|
||||
<span class=p>}</span>
|
||||
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=mh>0x82</span><span class=w> </span><span class=mh>0xa7</span><span class=w> </span><span class=mh>0x63</span><span class=w> </span><span class=mh>0x6f</span><span class=w> </span><span class=mh>0x6d</span><span class=w> </span><span class=mh>0x70</span><span class=w> </span><span class=mh>0x61</span><span class=w> </span><span class=mh>0x63</span><span class=w> </span><span class=mh>0x74</span><span class=w> </span><span class=mh>0xc3</span><span class=w> </span><span class=mh>0xa6</span><span class=w> </span><span class=mh>0x73</span><span class=w> </span><span class=mh>0x63</span><span class=w> </span><span class=mh>0x68</span><span class=w> </span><span class=mh>0x65</span><span class=w> </span><span class=mh>0x6d</span><span class=w> </span><span class=mh>0x61</span><span class=w> </span><span class=mh>0x00</span><span class=w> </span>
|
||||
</code></pre></div> </details> <h2 id=deserialization>Deserialization<a class=headerlink href=#deserialization title="Permanent link">¶</a></h2> <p>The library maps MessagePack types to <abbr title="JavaScript Object Notation">JSON</abbr> value types as follows:</p> <table> <thead> <tr> <th>MessagePack type</th> <th><abbr title="JavaScript Object Notation">JSON</abbr> value type</th> <th>first byte</th> </tr> </thead> <tbody> <tr> <td>positive fixint</td> <td>number_unsigned</td> <td>0x00..0x7F</td> </tr> <tr> <td>fixmap</td> <td>object</td> <td>0x80..0x8F</td> </tr> <tr> <td>fixarray</td> <td>array</td> <td>0x90..0x9F</td> </tr> <tr> <td>fixstr</td> <td>string</td> <td>0xA0..0xBF</td> </tr> <tr> <td>nil</td> <td><code>null</code></td> <td>0xC0</td> </tr> <tr> <td>false</td> <td><code>false</code></td> <td>0xC2</td> </tr> <tr> <td>true</td> <td><code>true</code></td> <td>0xC3</td> </tr> <tr> <td>float 32</td> <td>number_float</td> <td>0xCA</td> </tr> <tr> <td>float 64</td> <td>number_float</td> <td>0xCB</td> </tr> <tr> <td>uint 8</td> <td>number_unsigned</td> <td>0xCC</td> </tr> <tr> <td>uint 16</td> <td>number_unsigned</td> <td>0xCD</td> </tr> <tr> <td>uint 32</td> <td>number_unsigned</td> <td>0xCE</td> </tr> <tr> <td>uint 64</td> <td>number_unsigned</td> <td>0xCF</td> </tr> <tr> <td>int 8</td> <td>number_integer</td> <td>0xD0</td> </tr> <tr> <td>int 16</td> <td>number_integer</td> <td>0xD1</td> </tr> <tr> <td>int 32</td> <td>number_integer</td> <td>0xD2</td> </tr> <tr> <td>int 64</td> <td>number_integer</td> <td>0xD3</td> </tr> <tr> <td>str 8</td> <td>string</td> <td>0xD9</td> </tr> <tr> <td>str 16</td> <td>string</td> <td>0xDA</td> </tr> <tr> <td>str 32</td> <td>string</td> <td>0xDB</td> </tr> <tr> <td>array 16</td> <td>array</td> <td>0xDC</td> </tr> <tr> <td>array 32</td> <td>array</td> <td>0xDD</td> </tr> <tr> <td>map 16</td> <td>object</td> <td>0xDE</td> </tr> <tr> <td>map 32</td> <td>object</td> <td>0xDF</td> </tr> <tr> <td>bin 8</td> <td>binary</td> <td>0xC4</td> </tr> <tr> <td>bin 16</td> <td>binary</td> <td>0xC5</td> </tr> <tr> <td>bin 32</td> <td>binary</td> <td>0xC6</td> </tr> <tr> <td>ext 8</td> <td>binary</td> <td>0xC7</td> </tr> <tr> <td>ext 16</td> <td>binary</td> <td>0xC8</td> </tr> <tr> <td>ext 32</td> <td>binary</td> <td>0xC9</td> </tr> <tr> <td>fixext 1</td> <td>binary</td> <td>0xD4</td> </tr> <tr> <td>fixext 2</td> <td>binary</td> <td>0xD5</td> </tr> <tr> <td>fixext 4</td> <td>binary</td> <td>0xD6</td> </tr> <tr> <td>fixext 8</td> <td>binary</td> <td>0xD7</td> </tr> <tr> <td>fixext 16</td> <td>binary</td> <td>0xD8</td> </tr> <tr> <td>negative fixint</td> <td>number_integer</td> <td>0xE0-0xFF</td> </tr> </tbody> </table> <div class="admonition info"> <p class=admonition-title>Info</p> <p>Any MessagePack output created by <code>to_msgpack</code> can be successfully parsed by <code>from_msgpack</code>.</p> </div> <div class="admonition warning"> <p class=admonition-title>Object keys</p> <p>MessagePack allows map keys of any type, whereas <abbr title="JavaScript Object Notation">JSON</abbr> only allows strings as keys in object values. Like the <abbr title="JavaScript Object Notation">JSON</abbr>-compatible <a href="https://github.com/msgpack/msgpack/blob/master/spec.md#profile">profile</a> sketched in the MessagePack specification, this library restricts map keys to <code>str</code> values. Maps with keys of any other type are rejected with a <a href=../../../home/exceptions/#jsonexceptionparse_error113><code>parse_error.113</code></a> exception (or, with <code>allow_exceptions</code> set to <code>false</code>, a discarded value) naming the type of the key that was found, for instance:</p> <div class=highlight><pre><span></span><code>[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack object key: only string keys are supported, but found nil; last byte: 0xC0
|
||||
</code></pre></div> <p>This applies to the <a href=../../parsing/sax_interface/ ><abbr title="Simple API for XML">SAX</abbr> interface</a> as well, as the key is read before it is passed on. Such input needs a general-purpose MessagePack library instead.</p> </div> <div class="admonition warning"> <p class=admonition-title><abbr title="Unicode Transformation Format">UTF</abbr>-8 validation of string values</p> <p>The MessagePack specification requires <code>str</code> values (<code>fixstr</code>, <code>str 8</code>, <code>str 16</code>, <code>str 32</code>) to be valid <abbr title="Unicode Transformation Format">UTF</abbr>-8. This library validates the bytes of every such string (object keys included) at decode time and rejects ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8 with a <a href=../../../home/exceptions/#jsonexceptionparse_error113><code>parse_error.113</code></a> exception (or, with <code>allow_exceptions</code> set to <code>false</code>, a discarded value), rather than only failing later when the resulting value is dumped. <code>bin</code>/<code>ext</code>/<code>fixext</code> values are unaffected and are never validated, since they are not required to hold text.</p> </div> <details class=example> <summary>Example: deserialize a <abbr title="JavaScript Object Notation">JSON</abbr> value from MessagePack</summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
</code></pre></div> <p>This applies to the <a href=../../parsing/sax_interface/ ><abbr title="Simple API for XML">SAX</abbr> interface</a> as well, as the key is read before it is passed on. Such input needs a general-purpose MessagePack library instead.</p> </div> <div class="admonition warning"> <p class=admonition-title>Ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8 in string values</p> <p>The MessagePack specification explicitly allows a <code>str</code> value (<code>fixstr</code>, <code>str 8</code>, <code>str 16</code>, <code>str 32</code>) to contain a byte sequence that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8, and expects a deserializer to hand the original bytes back unchanged. This library follows that by default: with its <a href=../../../api/basic_json/from_msgpack/ ><code>error_handler</code></a> parameter left at <code>keep</code> (the default), <code>from_msgpack()</code> reads <code>str</code> bytes (object keys included) as-is, without validating them, so such a value round-trips through <code>from_msgpack(to_msgpack(j))</code> byte for byte. Passing <code>error_handler_t::strict</code> makes <code>from_msgpack()</code> check anyway and throw <a href=../../../home/exceptions/#jsonexceptionparse_error113><code>parse_error.113</code></a> for ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8, and <code>replace</code>/<code>ignore</code> sanitize the string instead of keeping it. <code>to_msgpack()</code> also writes <code>str</code> bytes as-is by default, since the specification permits it; its <a href=../../../api/basic_json/to_msgpack/ ><code>error_handler</code></a> parameter can be set to <code>strict</code> to throw <a href=../../../home/exceptions/#jsonexceptiontype_error316><code>type_error.316</code></a> instead, or to <code>replace</code>/<code>ignore</code> to sanitize the string, for instance for a decoder that rejects ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8. However, <a href=../../../api/basic_json/dump/ ><code>dump()</code></a> still requires valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and throws <a href=../../../home/exceptions/#jsonexceptiontype_error316><code>type_error.316</code></a> for a value read this way with the default <code>keep</code> handler, unless an error handler is passed that replaces or ignores the ill-formed bytes.</p> </div> <details class=example> <summary>Example: deserialize a <abbr title="JavaScript Object Notation">JSON</abbr> value from MessagePack</summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><iomanip></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span>
|
||||
|
||||
@@ -46,4 +46,4 @@
|
||||
<span class=w> </span><span class=nt>"compact"</span><span class=p>:</span><span class=w> </span><span class=kc>true</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=nt>"schema"</span><span class=p>:</span><span class=w> </span><span class=mi>0</span>
|
||||
<span class=p>}</span>
|
||||
</code></pre></div> </details> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 2, 2026 09:32:15 UTC">October 2, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - 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|
||||
</code></pre></div> </details> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 4, 2026 10:13:49 UTC">October 4, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - 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|
||||
@@ -162,9 +162,9 @@ MessagePack allows map keys of any type, whereas JSON only allows strings as key
|
||||
|
||||
This applies to the [SAX interface](https://json.nlohmann.me/features/parsing/sax_interface/index.md) as well, as the key is read before it is passed on. Such input needs a general-purpose MessagePack library instead.
|
||||
|
||||
UTF-8 validation of string values
|
||||
Ill-formed UTF-8 in string values
|
||||
|
||||
The MessagePack specification requires `str` values (`fixstr`, `str 8`, `str 16`, `str 32`) to be valid UTF-8. This library validates the bytes of every such string (object keys included) at decode time and rejects ill-formed UTF-8 with a [`parse_error.113`](https://json.nlohmann.me/home/exceptions/#jsonexceptionparse_error113) exception (or, with `allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting value is dumped. `bin`/`ext`/`fixext` values are unaffected and are never validated, since they are not required to hold text.
|
||||
The MessagePack specification explicitly allows a `str` value (`fixstr`, `str 8`, `str 16`, `str 32`) to contain a byte sequence that is not valid UTF-8, and expects a deserializer to hand the original bytes back unchanged. This library follows that by default: with its [`error_handler`](https://json.nlohmann.me/api/basic_json/from_msgpack/index.md) parameter left at `keep` (the default), `from_msgpack()` reads `str` bytes (object keys included) as-is, without validating them, so such a value round-trips through `from_msgpack(to_msgpack(j))` byte for byte. Passing `error_handler_t::strict` makes `from_msgpack()` check anyway and throw [`parse_error.113`](https://json.nlohmann.me/home/exceptions/#jsonexceptionparse_error113) for ill-formed UTF-8, and `replace`/`ignore` sanitize the string instead of keeping it. `to_msgpack()` also writes `str` bytes as-is by default, since the specification permits it; its [`error_handler`](https://json.nlohmann.me/api/basic_json/to_msgpack/index.md) parameter can be set to `strict` to throw [`type_error.316`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) instead, or to `replace`/`ignore` to sanitize the string, for instance for a decoder that rejects ill-formed UTF-8. However, [`dump()`](https://json.nlohmann.me/api/basic_json/dump/index.md) still requires valid UTF-8 and throws [`type_error.316`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) for a value read this way with the default `keep` handler, unless an error handler is passed that replaces or ignores the ill-formed bytes.
|
||||
|
||||
Example: deserialize a JSON value from MessagePack
|
||||
|
||||
|
||||
@@ -47,6 +47,15 @@ The library uses the following mapping from JSON values types to UBJSON types ac
|
||||
|
||||
- strings with more than 9223372036854775807 bytes (theoretical)
|
||||
|
||||
!!! warning "UTF-8 validation of string values and object keys"
|
||||
|
||||
UBJSON's required string encoding is UTF-8. By default (the [`error_handler`](../../api/basic_json/to_ubjson.md)
|
||||
parameter left at `keep`), `to_ubjson()` writes the bytes of string values and object keys unchanged, even if they
|
||||
are not valid UTF-8. With `error_handler_t::strict`, it throws
|
||||
[`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) for ill-formed UTF-8 instead;
|
||||
`replace`/`ignore` sanitize the string. [`JSON_STRICT_BINARY_UTF8`](../../api/macros/json_strict_binary_utf8.md)
|
||||
makes `strict` the default.
|
||||
|
||||
!!! info "Unused UBJSON markers"
|
||||
|
||||
The following markers are not used in the conversion:
|
||||
@@ -120,6 +129,19 @@ The library maps UBJSON types to JSON value types as follows:
|
||||
|
||||
The mapping is **complete** in the sense that any UBJSON value can be converted to a JSON value.
|
||||
|
||||
!!! warning "Ill-formed UTF-8 in string values and object keys"
|
||||
|
||||
UBJSON's required string encoding is UTF-8, but checking it on read is opt-in: with the
|
||||
[`error_handler`](../../api/basic_json/from_ubjson.md) parameter left at `keep` (the default), `from_ubjson()`
|
||||
accepts a string value or object key whose bytes are not valid UTF-8 and hands them back unchanged. Passing
|
||||
`error_handler_t::strict` makes `from_ubjson()` check and throw
|
||||
[`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) for ill-formed UTF-8, and
|
||||
`replace`/`ignore` sanitize the string instead of keeping it. However,
|
||||
[`dump()`](../../api/basic_json/dump.md) still requires valid UTF-8 and throws
|
||||
[`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) for a value read with the default
|
||||
`keep` handler, unless an error handler is passed that replaces or ignores the ill-formed bytes. `to_ubjson()`'s
|
||||
own `error_handler` parameter defaults to `keep` (see above), so such a value is written back unchanged.
|
||||
|
||||
??? example "Example: deserialize a JSON value from UBJSON"
|
||||
|
||||
```cpp
|
||||
|
||||
@@ -1,4 +1,4 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/ubjson/" rel="canonical"><link href=../messagepack/ rel=prev><link href=../../binary_values/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>UBJSON - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> UBJSON </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette 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|
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/features/binary_formats/ubjson/" rel="canonical"><link href=../messagepack/ rel=prev><link href=../../binary_values/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>UBJSON - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#ubjson class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> UBJSON </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </laLine truncated
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><iomanip></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span>
|
||||
|
||||
@@ -66,7 +66,7 @@
|
||||
<span class=p>[</span><span class=n>i1i2i3i4i5i6i7i8</span><span class=p>]</span>
|
||||
<span class=p>[</span><span class=err>#</span><span class=n>i8i1i2i3i4i5i6i7i8</span>
|
||||
<span class=p>[</span><span class=n>$i</span><span class=err>#</span><span class=n>i812345678</span>
|
||||
</code></pre></div> </details> <h2 id=deserialization>Deserialization<a class=headerlink href=#deserialization title="Permanent link">¶</a></h2> <p>The library maps <abbr title="Universal Binary JSON">UBJSON</abbr> types to <abbr title="JavaScript Object Notation">JSON</abbr> value types as follows:</p> <table> <thead> <tr> <th><abbr title="Universal Binary JSON">UBJSON</abbr> type</th> <th><abbr title="JavaScript Object Notation">JSON</abbr> value type</th> <th>marker</th> </tr> </thead> <tbody> <tr> <td>no-op</td> <td><em>no value, next value is read</em></td> <td><code>N</code></td> </tr> <tr> <td>null</td> <td><code>null</code></td> <td><code>Z</code></td> </tr> <tr> <td>false</td> <td><code>false</code></td> <td><code>F</code></td> </tr> <tr> <td>true</td> <td><code>true</code></td> <td><code>T</code></td> </tr> <tr> <td>float32</td> <td>number_float</td> <td><code>d</code></td> </tr> <tr> <td>float64</td> <td>number_float</td> <td><code>D</code></td> </tr> <tr> <td>uint8</td> <td>number_unsigned</td> <td><code>U</code></td> </tr> <tr> <td>int8</td> <td>number_integer</td> <td><code>i</code></td> </tr> <tr> <td>int16</td> <td>number_integer</td> <td><code>I</code></td> </tr> <tr> <td>int32</td> <td>number_integer</td> <td><code>l</code></td> </tr> <tr> <td>int64</td> <td>number_integer</td> <td><code>L</code></td> </tr> <tr> <td>string</td> <td>string</td> <td><code>S</code></td> </tr> <tr> <td>char</td> <td>string</td> <td><code>C</code></td> </tr> <tr> <td>array</td> <td>array (optimized values are supported)</td> <td><code>[</code></td> </tr> <tr> <td>object</td> <td>object (optimized values are supported)</td> <td><code>{</code></td> </tr> </tbody> </table> <div class="admonition success"> <p class=admonition-title>Complete mapping</p> <p>The mapping is <strong>complete</strong> in the sense that any <abbr title="Universal Binary JSON">UBJSON</abbr> value can be converted to a <abbr title="JavaScript Object Notation">JSON</abbr> value.</p> </div> <details class=example> <summary>Example: deserialize a <abbr title="JavaScript Object Notation">JSON</abbr> value from <abbr title="Universal Binary JSON">UBJSON</abbr></summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
</code></pre></div> </details> <h2 id=deserialization>Deserialization<a class=headerlink href=#deserialization title="Permanent link">¶</a></h2> <p>The library maps <abbr title="Universal Binary JSON">UBJSON</abbr> types to <abbr title="JavaScript Object Notation">JSON</abbr> value types as follows:</p> <table> <thead> <tr> <th><abbr title="Universal Binary JSON">UBJSON</abbr> type</th> <th><abbr title="JavaScript Object Notation">JSON</abbr> value type</th> <th>marker</th> </tr> </thead> <tbody> <tr> <td>no-op</td> <td><em>no value, next value is read</em></td> <td><code>N</code></td> </tr> <tr> <td>null</td> <td><code>null</code></td> <td><code>Z</code></td> </tr> <tr> <td>false</td> <td><code>false</code></td> <td><code>F</code></td> </tr> <tr> <td>true</td> <td><code>true</code></td> <td><code>T</code></td> </tr> <tr> <td>float32</td> <td>number_float</td> <td><code>d</code></td> </tr> <tr> <td>float64</td> <td>number_float</td> <td><code>D</code></td> </tr> <tr> <td>uint8</td> <td>number_unsigned</td> <td><code>U</code></td> </tr> <tr> <td>int8</td> <td>number_integer</td> <td><code>i</code></td> </tr> <tr> <td>int16</td> <td>number_integer</td> <td><code>I</code></td> </tr> <tr> <td>int32</td> <td>number_integer</td> <td><code>l</code></td> </tr> <tr> <td>int64</td> <td>number_integer</td> <td><code>L</code></td> </tr> <tr> <td>string</td> <td>string</td> <td><code>S</code></td> </tr> <tr> <td>char</td> <td>string</td> <td><code>C</code></td> </tr> <tr> <td>array</td> <td>array (optimized values are supported)</td> <td><code>[</code></td> </tr> <tr> <td>object</td> <td>object (optimized values are supported)</td> <td><code>{</code></td> </tr> </tbody> </table> <div class="admonition success"> <p class=admonition-title>Complete mapping</p> <p>The mapping is <strong>complete</strong> in the sense that any <abbr title="Universal Binary JSON">UBJSON</abbr> value can be converted to a <abbr title="JavaScript Object Notation">JSON</abbr> value.</p> </div> <div class="admonition warning"> <p class=admonition-title>Ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8 in string values and object keys</p> <p><abbr title="Universal Binary JSON">UBJSON</abbr>'s required string encoding is <abbr title="Unicode Transformation Format">UTF</abbr>-8, but checking it on read is opt-in: with the <a href=../../../api/basic_json/from_ubjson/ ><code>error_handler</code></a> parameter left at <code>keep</code> (the default), <code>from_ubjson()</code> accepts a string value or object key whose bytes are not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and hands them back unchanged. Passing <code>error_handler_t::strict</code> makes <code>from_ubjson()</code> check and throw <a href=../../../home/exceptions/#jsonexceptionparse_error113><code>parse_error.113</code></a> for ill-formed <abbr title="Unicode Transformation Format">UTF</abbr>-8, and <code>replace</code>/<code>ignore</code> sanitize the string instead of keeping it. However, <a href=../../../api/basic_json/dump/ ><code>dump()</code></a> still requires valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and throws <a href=../../../home/exceptions/#jsonexceptiontype_error316><code>type_error.316</code></a> for a value read with the default <code>keep</code> handler, unless an error handler is passed that replaces or ignores the ill-formed bytes. <code>to_ubjson()</code>'s own <code>error_handler</code> parameter defaults to <code>keep</code> (see above), so such a value is written back unchanged.</p> </div> <details class=example> <summary>Example: deserialize a <abbr title="JavaScript Object Notation">JSON</abbr> value from <abbr title="Universal Binary JSON">UBJSON</abbr></summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><iomanip></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span>
|
||||
|
||||
@@ -90,4 +90,4 @@
|
||||
<span class=w> </span><span class=nt>"compact"</span><span class=p>:</span><span class=w> </span><span class=kc>true</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=nt>"schema"</span><span class=p>:</span><span class=w> </span><span class=mi>0</span>
|
||||
<span class=p>}</span>
|
||||
</code></pre></div> </details> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 2, 2026 09:32:15 UTC">October 2, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - 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|
||||
</code></pre></div> </details> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 4, 2026 10:13:49 UTC">October 4, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - 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|
||||
@@ -46,6 +46,10 @@ The following values can **not** be converted to a UBJSON value:
|
||||
|
||||
- strings with more than 9223372036854775807 bytes (theoretical)
|
||||
|
||||
UTF-8 validation of string values and object keys
|
||||
|
||||
UBJSON's required string encoding is UTF-8. By default (the [`error_handler`](https://json.nlohmann.me/api/basic_json/to_ubjson/index.md) parameter left at `keep`), `to_ubjson()` writes the bytes of string values and object keys unchanged, even if they are not valid UTF-8. With `error_handler_t::strict`, it throws [`type_error.316`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) for ill-formed UTF-8 instead; `replace`/`ignore` sanitize the string. [`JSON_STRICT_BINARY_UTF8`](https://json.nlohmann.me/api/macros/json_strict_binary_utf8/index.md) makes `strict` the default.
|
||||
|
||||
Unused UBJSON markers
|
||||
|
||||
The following markers are not used in the conversion:
|
||||
@@ -173,6 +177,10 @@ Complete mapping
|
||||
|
||||
The mapping is **complete** in the sense that any UBJSON value can be converted to a JSON value.
|
||||
|
||||
Ill-formed UTF-8 in string values and object keys
|
||||
|
||||
UBJSON's required string encoding is UTF-8, but checking it on read is opt-in: with the [`error_handler`](https://json.nlohmann.me/api/basic_json/from_ubjson/index.md) parameter left at `keep` (the default), `from_ubjson()` accepts a string value or object key whose bytes are not valid UTF-8 and hands them back unchanged. Passing `error_handler_t::strict` makes `from_ubjson()` check and throw [`parse_error.113`](https://json.nlohmann.me/home/exceptions/#jsonexceptionparse_error113) for ill-formed UTF-8, and `replace`/`ignore` sanitize the string instead of keeping it. However, [`dump()`](https://json.nlohmann.me/api/basic_json/dump/index.md) still requires valid UTF-8 and throws [`type_error.316`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) for a value read with the default `keep` handler, unless an error handler is passed that replaces or ignores the ill-formed bytes. `to_ubjson()`'s own `error_handler` parameter defaults to `keep` (see above), so such a value is written back unchanged.
|
||||
|
||||
Example: deserialize a JSON value from UBJSON
|
||||
|
||||
```
|
||||
|
||||
Reference in new issue
Block a user