deploy: 4155e2938f
This commit is contained in:
1 parent
be4d0a6f4b
commit
90f0c9d411
714 files changed
+22067
-622
No files matched your search
@@ -0,0 +1,74 @@
|
||||
<!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/api/basic_json_document/parse/" rel="canonical"><link href=../owns_source/ rel=prev><link href=../parse_copy/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>parse - 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=#nlohmannbasic_json_documentparse 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> parse </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.Line truncated
|
||||
<span class=k>template</span><span class=o><</span><span class=k>typename</span><span class=w> </span><span class=nc>InputType</span><span class=o>></span>
|
||||
<span class=k>static</span><span class=w> </span><span class=n>basic_json_document</span><span class=w> </span><span class=n>parse</span><span class=p>(</span><span class=n>InputType</span><span class=o>&&</span><span class=w> </span><span class=n>input</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=kt>bool</span><span class=w> </span><span class=n>allow_exceptions</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=nb>true</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=kt>bool</span><span class=w> </span><span class=n>ignore_comments</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=nb>false</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=kt>bool</span><span class=w> </span><span class=n>ignore_trailing_commas</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=nb>false</span><span class=p>);</span>
|
||||
|
||||
<span class=c1>// (2)</span>
|
||||
<span class=k>template</span><span class=o><</span><span class=k>typename</span><span class=w> </span><span class=nc>IteratorType</span><span class=o>></span>
|
||||
<span class=k>static</span><span class=w> </span><span class=n>basic_json_document</span><span class=w> </span><span class=n>parse</span><span class=p>(</span><span class=n>IteratorType</span><span class=w> </span><span class=n>first</span><span class=p>,</span><span class=w> </span><span class=n>IteratorType</span><span class=w> </span><span class=n>last</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=kt>bool</span><span class=w> </span><span class=n>allow_exceptions</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=nb>true</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=kt>bool</span><span class=w> </span><span class=n>ignore_comments</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=nb>false</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=kt>bool</span><span class=w> </span><span class=n>ignore_trailing_commas</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=nb>false</span><span class=p>);</span>
|
||||
</code></pre></div> <ol> <li>Deserialize from a compatible input, borrowing or owning it depending on its value category and type (see Notes).</li> <li>Deserialize from a pair of input iterators.</li> </ol> <p>Both overloads accept the same <abbr title="JavaScript Object Notation">JSON</abbr> text as <a href=../../basic_json/parse/ ><code>BasicJsonType::parse()</code></a>, with the same <code>ignore_comments</code>/<code>ignore_trailing_commas</code> options, but build a <a href=../ ><code>basic_json_document</code></a> (a flat index into the input) instead of a tree of <code>BasicJsonType</code> values. They take the same inputs as <code>BasicJsonType::parse()</code>. Byte inputs that stay alive can be borrowed; all others (streams, <code class=highlight><span class=kt>FILE</span><span class=o>*</span></code>, wide characters, non-contiguous iterators) are read into a copy that the document owns -- see the Notes. Use <a href=../parse_copy/ ><code>parse_copy()</code></a> to get an owned copy of a borrowable input as well.</p> <h2 id=template-parameters>Template parameters<a class=headerlink href=#template-parameters title="Permanent link">¶</a></h2> <dl> <dt><code>InputType</code></dt> <dd> <p>A compatible input, for instance:</p> <ul> <li>a <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>string</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>string_view</span></code>, or a C-style array of single-byte characters</li> <li>a pointer to a null-terminated string of single-byte characters (<code class=highlight><span class=kt>char</span></code>, <code class=highlight><span class=kt>signed</span><span class=w> </span><span class=kt>char</span></code>, <code class=highlight><span class=kt>unsigned</span><span class=w> </span><span class=kt>char</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=kt>uint8_t</span></code>)</li> <li>a container for which <code class=highlight><span class=n>obj</span><span class=p>.</span><span class=n>data</span><span class=p>()</span></code> and <code class=highlight><span class=n>obj</span><span class=p>.</span><span class=n>size</span><span class=p>()</span></code> give contiguous single-byte access, e.g. <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o><</span><span class=kt>char</span><span class=o>></span></code> or <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o><</span><span class=n>std</span><span class=o>::</span><span class=kt>uint8_t</span><span class=o>></span></code></li> <li>an <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>istream</span></code> object</li> <li>a <code class=highlight><span class=kt>FILE</span><span class=o>*</span></code> pointer</li> <li>wide characters (<code class=highlight><span class=kt>wchar_t</span></code>, <code class=highlight><span class=kt>char16_t</span></code>, <code class=highlight><span class=kt>char32_t</span></code>), which are converted to <abbr title="Unicode Transformation Format">UTF</abbr>-8: a wide string object (<code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>wstring</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>u16string</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>u32string</span></code>), an array (e.g. a wide string literal), or a pointer to a null-terminated wide string</li> </ul> </dd> <dt><code>IteratorType</code></dt> <dd>an input iterator type, for instance a pair of pointers such as <code>ptr</code> and <code>ptr + len</code>, or a pair of <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=o>::</span><span class=n>iterator</span></code>; the iterators of single-byte characters are borrowed or read like the byte inputs above, those of wide characters are converted to <abbr title="Unicode Transformation Format">UTF</abbr>-8</dd> </dl> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">¶</a></h2> <dl> <dt><code>input</code> (in)</dt> <dd>Input to parse from.</dd> <dt><code>allow_exceptions</code> (in)</dt> <dd>whether to throw exceptions in case of a parse error (optional, <code class=highlight><span class=nb>true</span></code> by default)</dd> <dt><code>ignore_comments</code> (in)</dt> <dd>whether comments should be ignored and treated like whitespace (<code class=highlight><span class=nb>true</span></code>) or yield a parse error (<code class=highlight><span class=nb>false</span></code>); (optional, <code class=highlight><span class=nb>false</span></code> by default)</dd> <dt><code>ignore_trailing_commas</code> (in)</dt> <dd>whether trailing commas in arrays or objects should be ignoLine truncated
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><string></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
<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>boolalpha</span><span class=p>;</span>
|
||||
|
||||
<span class=w> </span><span class=c1>// an lvalue std::string is BORROWED: the document only stores a pointer</span>
|
||||
<span class=w> </span><span class=c1>// into `text`, so `text` must outlive `borrowed`</span>
|
||||
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=w> </span><span class=n>text</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=sa>R</span><span class=s>"</span><span class=dl>(</span><span class=s>{"count": 3}</span><span class=dl>)</span><span class=s>"</span><span class=p>;</span>
|
||||
<span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=n>borrowed</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>json_document</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=n>text</span><span class=p>);</span>
|
||||
<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>borrowed</span><span class=p>.</span><span class=n>owns_source</span><span class=p>()</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=sc>'\n'</span><span class=p>;</span><span class=w> </span><span class=c1>// false</span>
|
||||
|
||||
<span class=w> </span><span class=c1>// an rvalue std::string is MOVED into the document -- no copy of the text</span>
|
||||
<span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=n>owned</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>json_document</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=p>(</span><span class=sa>R</span><span class=s>"</span><span class=dl>(</span><span class=s>{"count": 3}</span><span class=dl>)</span><span class=s>"</span><span class=p>));</span>
|
||||
<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>owned</span><span class=p>.</span><span class=n>owns_source</span><span class=p>()</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=sc>'\n'</span><span class=p>;</span><span class=w> </span><span class=c1>// true</span>
|
||||
|
||||
<span class=w> </span><span class=c1>// errors are identical to basic_json::parse: same exception id, message,</span>
|
||||
<span class=w> </span><span class=c1>// and position, because the library parser runs on the same bytes on a</span>
|
||||
<span class=w> </span><span class=c1>// failing input</span>
|
||||
<span class=w> </span><span class=k>try</span>
|
||||
<span class=w> </span><span class=p>{</span>
|
||||
<span class=w> </span><span class=k>static_cast</span><span class=o><</span><span class=kt>void</span><span class=o>></span><span class=p>(</span><span class=n>json_document</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=sa>R</span><span class=s>"</span><span class=dl>(</span><span class=s>{"count": </span><span class=dl>)</span><span class=s>"</span><span class=p>));</span>
|
||||
<span class=w> </span><span class=p>}</span>
|
||||
<span class=w> </span><span class=k>catch</span><span class=w> </span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>::</span><span class=n>parse_error</span><span class=o>&</span><span class=w> </span><span class=n>e</span><span class=p>)</span>
|
||||
<span class=w> </span><span class=p>{</span>
|
||||
<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>e</span><span class=p>.</span><span class=n>id</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=sc>'\n'</span><span class=p>;</span>
|
||||
<span class=w> </span><span class=p>}</span>
|
||||
<span class=p>}</span>
|
||||
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=kc>false</span>
|
||||
<span class=kc>true</span>
|
||||
<span class=mi>101</span>
|
||||
</code></pre></div> </details> <details class=example> <summary>Example: (2) parse an iterator range (no NUL terminator required)</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><vector></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
<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>boolalpha</span><span class=p>;</span>
|
||||
|
||||
<span class=w> </span><span class=c1>// a JSON value embedded in a larger, non-null-terminated buffer (e.g. a</span>
|
||||
<span class=w> </span><span class=c1>// slice received over the network)</span>
|
||||
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o><</span><span class=kt>char</span><span class=o>></span><span class=w> </span><span class=n>buffer</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=p>{</span><span class=sc>'['</span><span class=p>,</span><span class=w> </span><span class=sc>'1'</span><span class=p>,</span><span class=w> </span><span class=sc>','</span><span class=p>,</span><span class=w> </span><span class=sc>'2'</span><span class=p>,</span><span class=w> </span><span class=sc>']'</span><span class=p>,</span><span class=w> </span><span class=sc>'j'</span><span class=p>,</span><span class=w> </span><span class=sc>'u'</span><span class=p>,</span><span class=w> </span><span class=sc>'n'</span><span class=p>,</span><span class=w> </span><span class=sc>'k'</span><span class=p>};</span>
|
||||
|
||||
<span class=w> </span><span class=c1>// a pointer pair is BORROWED, exactly like a byte container lvalue: the</span>
|
||||
<span class=w> </span><span class=c1>// document points into the buffer. (From C++20 on, std::vector<char></span>
|
||||
<span class=w> </span><span class=c1>// iterators are borrowed as well; before, they are copied.)</span>
|
||||
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=kt>char</span><span class=o>*</span><span class=w> </span><span class=n>first</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>buffer</span><span class=p>.</span><span class=n>data</span><span class=p>();</span>
|
||||
<span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=n>doc</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>json_document</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=n>first</span><span class=p>,</span><span class=w> </span><span class=n>first</span><span class=w> </span><span class=o>+</span><span class=w> </span><span class=mi>5</span><span class=p>);</span>
|
||||
<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>doc</span><span class=p>.</span><span class=n>root</span><span class=p>().</span><span class=n>is_array</span><span class=p>()</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=sc>' '</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=n>doc</span><span class=p>.</span><span class=n>root</span><span class=p>().</span><span class=n>size</span><span class=p>()</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=sc>'\n'</span><span class=p>;</span>
|
||||
<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>doc</span><span class=p>.</span><span class=n>owns_source</span><span class=p>()</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=sc>'\n'</span><span class=p>;</span><span class=w> </span><span class=c1>// false: borrowed</span>
|
||||
<span class=p>}</span>
|
||||
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=kc>true</span><span class=w> </span><span class=mi>2</span>
|
||||
<span class=kc>false</span>
|
||||
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li><a href=../parse_copy/ >parse_copy</a> - deserialize a copy of a compatible input</li> <li><a href=../accept/ >accept</a> - check whether the input is valid <abbr title="JavaScript Object Notation">JSON</abbr></li> <li><a href=../read/ >read</a> - (re-)parse into this document, reusing its memory</li> <li><a href=../owns_source/ >owns_source</a> - return whether the document holds its own copy of the text</li> <li><a href=../load/ >load</a> - read a document from an image instead of parsing <abbr title="JavaScript Object Notation">JSON</abbr> text</li> <li><a href=../../basic_json/parse/ ><code>BasicJsonType::parse</code></a> - the corresponding function of <code>basic_json</code></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">¶</a></h2> <ul> <li>Added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> </ul> <!-- 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 21, 2026 08:21:29 UTC">October 21, 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 - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><patLine truncated
|
||||
@@ -0,0 +1,181 @@
|
||||
# nlohmann::basic_json_document::parse
|
||||
|
||||
```
|
||||
// (1)
|
||||
template<typename InputType>
|
||||
static basic_json_document parse(InputType&& input,
|
||||
const bool allow_exceptions = true,
|
||||
const bool ignore_comments = false,
|
||||
const bool ignore_trailing_commas = false);
|
||||
|
||||
// (2)
|
||||
template<typename IteratorType>
|
||||
static basic_json_document parse(IteratorType first, IteratorType last,
|
||||
const bool allow_exceptions = true,
|
||||
const bool ignore_comments = false,
|
||||
const bool ignore_trailing_commas = false);
|
||||
```
|
||||
|
||||
1. Deserialize from a compatible input, borrowing or owning it depending on its value category and type (see Notes).
|
||||
1. Deserialize from a pair of input iterators.
|
||||
|
||||
Both overloads accept the same JSON text as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md), with the same `ignore_comments`/`ignore_trailing_commas` options, but build a [`basic_json_document`](https://json.nlohmann.me/api/basic_json_document/index.md) (a flat index into the input) instead of a tree of `BasicJsonType` values. They take the same inputs as `BasicJsonType::parse()`. Byte inputs that stay alive can be borrowed; all others (streams, `FILE*`, wide characters, non-contiguous iterators) are read into a copy that the document owns -- see the Notes. Use [`parse_copy()`](https://json.nlohmann.me/api/basic_json_document/parse_copy/index.md) to get an owned copy of a borrowable input as well.
|
||||
|
||||
## Template parameters
|
||||
|
||||
`InputType` : A compatible input, for instance:
|
||||
|
||||
```
|
||||
- a `std::string`, `std::string_view`, or a C-style array of single-byte characters
|
||||
- a pointer to a null-terminated string of single-byte characters (`char`, `signed char`,
|
||||
`unsigned char`, `std::uint8_t`)
|
||||
- a container for which `obj.data()` and `obj.size()` give contiguous single-byte access, e.g.
|
||||
`std::vector<char>` or `std::vector<std::uint8_t>`
|
||||
- an `std::istream` object
|
||||
- a `FILE*` pointer
|
||||
- wide characters (`wchar_t`, `char16_t`, `char32_t`), which are converted to UTF-8: a wide
|
||||
string object (`std::wstring`, `std::u16string`, `std::u32string`), an array (e.g. a wide
|
||||
string literal), or a pointer to a null-terminated wide string
|
||||
```
|
||||
|
||||
`IteratorType` : an input iterator type, for instance a pair of pointers such as `ptr` and `ptr + len`, or a pair of `std::string::iterator`; the iterators of single-byte characters are borrowed or read like the byte inputs above, those of wide characters are converted to UTF-8
|
||||
|
||||
## Parameters
|
||||
|
||||
`input` (in) : Input to parse from.
|
||||
|
||||
`allow_exceptions` (in) : whether to throw exceptions in case of a parse error (optional, `true` by default)
|
||||
|
||||
`ignore_comments` (in) : whether comments should be ignored and treated like whitespace (`true`) or yield a parse error (`false`); (optional, `false` by default)
|
||||
|
||||
`ignore_trailing_commas` (in) : whether trailing commas in arrays or objects should be ignored and treated like whitespace (`true`) or yield a parse error (`false`); (optional, `false` by default)
|
||||
|
||||
`first` (in) : iterator to the start of a character range
|
||||
|
||||
`last` (in) : iterator to the end of a character range
|
||||
|
||||
## Return value
|
||||
|
||||
The parsed document. If `allow_exceptions` is `false` and the input is not valid JSON, the returned document is discarded; see [`is_discarded`](https://json.nlohmann.me/api/basic_json_document/is_discarded/index.md).
|
||||
|
||||
## Exceptions
|
||||
|
||||
Throws the same exception [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) throws for the same input and options -- the same exception id, message, and position -- because on a failing input the library's own parser is run on the same bytes to produce the diagnostic. This replay runs only for a failing input, and costs about a lexing pass up to the error (its SAX handler builds no values); with `allow_exceptions` set to `false`, it is skipped and a discarded document is returned instead. Additionally throws [`out_of_range.416`](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range416) if the input is 4294967280 bytes (4 GiB minus 16 bytes) or larger, a size [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) does not reject.
|
||||
|
||||
## Complexity
|
||||
|
||||
Linear in the length of the input.
|
||||
|
||||
## Notes
|
||||
|
||||
**Ownership.** Whether the document borrows `input` or owns a copy of it depends on its value category and type:
|
||||
|
||||
| `input` | ownership |
|
||||
| -------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------- |
|
||||
| lvalue byte container (`std::string`, `std::vector<char>`, ...), `std::string_view`, C string, character array | **borrowed** -- `input` must outlive the document |
|
||||
| non-const rvalue `std::string` | **owned**, moved in without a copy |
|
||||
| other rvalue byte container (including a `const` rvalue `std::string`) | **owned**, copied |
|
||||
| stream, `FILE*`, wide characters, or anything else read through the general input adapter | **owned**, read into a buffer (a stream is read to its end) |
|
||||
|
||||
For overload (2), a pair of pointers to single-byte integers (e.g. `const char*`, `std::uint8_t*`) is borrowed. From C++20 on, so is any other contiguous iterator over single bytes, such as `std::vector<char>::iterator` or `std::string::const_iterator`. Before C++20 these iterators cannot be told apart from other class-type iterators, so their range is read into an owned buffer, as is any non-contiguous range (e.g. of a `std::list<char>`).
|
||||
|
||||
See [`owns_source`](https://json.nlohmann.me/api/basic_json_document/owns_source/index.md) to check which happened after a call, and the [feature page](https://json.nlohmann.me/features/json_view/index.md) for the reasoning.
|
||||
|
||||
**Numbers.** As for [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md), an integer literal too large for the 64-bit integer type becomes a floating-point value.
|
||||
|
||||
**No lengths.** An integer argument that is not a `bool` where the flags are expected -- for example `parse(ptr, len)` -- does not compile (the overload is deleted). Such a call would convert `len` to `allow_exceptions` and read `ptr` as a null-terminated string, past the end of a buffer that has none. To parse a buffer of a given length, pass a pair of pointers: `parse(ptr, ptr + len)`. The same holds for [`parse_copy`](https://json.nlohmann.me/api/basic_json_document/parse_copy/index.md), [`accept`](https://json.nlohmann.me/api/basic_json_document/accept/index.md), and [`read`](https://json.nlohmann.me/api/basic_json_document/read/index.md).
|
||||
|
||||
## Examples
|
||||
|
||||
Example: (1) borrowed vs. owned input, and errors identical to `BasicJsonType::parse()`
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <string>
|
||||
#include <nlohmann/json.hpp>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
std::cout << std::boolalpha;
|
||||
|
||||
// an lvalue std::string is BORROWED: the document only stores a pointer
|
||||
// into `text`, so `text` must outlive `borrowed`
|
||||
std::string text = R"({"count": 3})";
|
||||
json_document borrowed = json_document::parse(text);
|
||||
std::cout << borrowed.owns_source() << '\n'; // false
|
||||
|
||||
// an rvalue std::string is MOVED into the document -- no copy of the text
|
||||
json_document owned = json_document::parse(std::string(R"({"count": 3})"));
|
||||
std::cout << owned.owns_source() << '\n'; // true
|
||||
|
||||
// errors are identical to basic_json::parse: same exception id, message,
|
||||
// and position, because the library parser runs on the same bytes on a
|
||||
// failing input
|
||||
try
|
||||
{
|
||||
static_cast<void>(json_document::parse(R"({"count": )"));
|
||||
}
|
||||
catch (const nlohmann::json::parse_error& e)
|
||||
{
|
||||
std::cout << e.id << '\n';
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
false
|
||||
true
|
||||
101
|
||||
```
|
||||
|
||||
Example: (2) parse an iterator range (no NUL terminator required)
|
||||
|
||||
```
|
||||
#include <iostream>
|
||||
#include <vector>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
std::cout << std::boolalpha;
|
||||
|
||||
// a JSON value embedded in a larger, non-null-terminated buffer (e.g. a
|
||||
// slice received over the network)
|
||||
std::vector<char> buffer = {'[', '1', ',', '2', ']', 'j', 'u', 'n', 'k'};
|
||||
|
||||
// a pointer pair is BORROWED, exactly like a byte container lvalue: the
|
||||
// document points into the buffer. (From C++20 on, std::vector<char>
|
||||
// iterators are borrowed as well; before, they are copied.)
|
||||
const char* first = buffer.data();
|
||||
json_document doc = json_document::parse(first, first + 5);
|
||||
std::cout << doc.root().is_array() << ' ' << doc.root().size() << '\n';
|
||||
std::cout << doc.owns_source() << '\n'; // false: borrowed
|
||||
}
|
||||
```
|
||||
|
||||
Output:
|
||||
|
||||
```
|
||||
true 2
|
||||
false
|
||||
```
|
||||
|
||||
## See also
|
||||
|
||||
- [parse_copy](https://json.nlohmann.me/api/basic_json_document/parse_copy/index.md) - deserialize a copy of a compatible input
|
||||
- [accept](https://json.nlohmann.me/api/basic_json_document/accept/index.md) - check whether the input is valid JSON
|
||||
- [read](https://json.nlohmann.me/api/basic_json_document/read/index.md) - (re-)parse into this document, reusing its memory
|
||||
- [owns_source](https://json.nlohmann.me/api/basic_json_document/owns_source/index.md) - return whether the document holds its own copy of the text
|
||||
- [load](https://json.nlohmann.me/api/basic_json_document/load/index.md) - read a document from an image instead of parsing JSON text
|
||||
- [`BasicJsonType::parse`](https://json.nlohmann.me/api/basic_json/parse/index.md) - the corresponding function of `basic_json`
|
||||
|
||||
## Version history
|
||||
|
||||
- Added in version 3.13.0 unreleased.
|
||||
Reference in new issue
Block a user