Fix clang-tidy modernize-use-auto in json_view from_json tests

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasCxh8jKXBaa6HBx9Xk
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/mkdocs/docs/features/json_view.md

@@ -253,6 +253,34 @@ Two conversions never copy at all:
 
 Both results are only valid as long as the view — and, for a string with no escapes, the borrowed source text — is.
 
+### `string_view` members
+
+A struct whose member is a `#!cpp std::string_view` (C++17) can be decoded from a view with the
+`NLOHMANN_DEFINE_TYPE_*` macros, and the member is not copied either: for a string without escape sequences it points
+into the document's source text, and for a string with escape sequences into the document's buffer of decoded strings.
+The member is valid as long as the document is alive and, for a document that
+[borrows its source text](#ownership-and-lifetime) (as [`parse()`](../api/basic_json_document/parse.md) does for
+an lvalue `#!cpp std::string`, a `#!cpp std::string_view`, or a C string), as long as that text is.
+
+```cpp
+struct record
+{
+    std::string_view name;
+    int count;
+    NLOHMANN_DEFINE_TYPE_INTRUSIVE(record, name, count)
+};
+
+const std::string text = R"({"name": "widget", "count": 3})";
+const json_document doc = json_document::parse(text);  // borrows text
+const record r = doc.root().get<record>();             // r.name points into text, valid while text and doc are
+```
+
+!!! warning "Decoding into a `string_view` from a `json` value dangles at once"
+
+    The same struct also compiles with `#!cpp json::parse(text).get<record>()`, but there `name` points into the
+    temporary `json` value, which is destroyed at the end of the statement. Use a named
+    [`json_document`](../api/json_document.md), as above, to decode such a struct.
+
 ## Writing generic code
 
 A view's type names its `BasicJsonType` and its [`view_mode`](../api/view_mode.md):

include/nlohmann/detail/input/binary_reader.hpp

@@ -4293,19 +4293,6 @@ class binary_reader
         return get_bytes(len, "string", result);
     }
 
-    /// whether @a s is valid UTF-8: ASCII eight bytes at a time, the rest
-    /// sequence by sequence (as the binary writers check strings)
-    static bool is_valid_utf8_string(const string_t& s, std::true_type /*is_byte*/) noexcept
-    {
-        return valid_utf8_string(reinterpret_cast<const unsigned char*>(s.data()), s.size());
-    }
-
-    /// whether @a s, of a character type wider than a byte, is valid UTF-8
-    static bool is_valid_utf8_string(const string_t& s, std::false_type /*is_byte*/) noexcept
-    {
-        return is_valid_utf8(s);
-    }
-
     /*!
     @brief validate a decoded text string (value or object key) against @ref error_handler
 
@@ -4325,16 +4312,7 @@ class binary_reader
     */
     bool check_string_utf8(string_t& result, const char* context)
     {
-        return error_handler == error_handler_t::keep || check_string_utf8_handler(result, context);
-    }
-
-    /// @ref check_string_utf8 for an error handler other than @ref
-    /// error_handler_t::keep; out of line, so that reading strings without a
-    /// check does not pay for the code of the check
-    JSON_HEDLEY_NEVER_INLINE
-    bool check_string_utf8_handler(string_t& result, const char* context)
-    {
-        if (is_valid_utf8_string(result, std::integral_constant<bool, sizeof(typename string_t::value_type) == 1>()))
+        if (error_handler == error_handler_t::keep || is_valid_utf8(result))
         {
             return true;
         }

include/nlohmann/detail/input/simd_scan.hpp

@@ -322,78 +322,6 @@ JSON_SCAN_SSSE3_TARGET JSON_HEDLEY_NEVER_INLINE inline bool vector_utf8_run(cons
     block_out = block;
     return false;
 }
-
-/*!
-@brief skip 16-byte blocks of well-formed UTF-8 at p (a character boundary)
-
-Like vector_utf8_run, but quotes, backslashes, and control characters are
-ordinary characters. Returns the start of the first block in which the check
-found an error (which may belong to a sequence begun in the block before) or
-where fewer than 16 bytes are left; a sequence may be cut at that point, so the
-caller resumes at its start, one sequence at a time.
-*/
-JSON_SCAN_SSSE3_TARGET JSON_HEDLEY_NEVER_INLINE inline const unsigned char* vector_utf8_valid_blocks(const unsigned char* block, const unsigned char* e) noexcept
-{
-    using lookup = utf8_lookup4<>;
-#if JSON_SCAN_NEON
-    const uint8x16_t t1h = vld1q_u8(lookup::byte_1_high.data());
-    const uint8x16_t t1l = vld1q_u8(lookup::byte_1_low.data());
-    const uint8x16_t t2h = vld1q_u8(lookup::byte_2_high.data());
-    uint8x16_t prev = vdupq_n_u8(0);
-    while (e - block >= 16)
-    {
-        const uint8x16_t in = vld1q_u8(block);
-        if (vmaxvq_u8(vorrq_u8(in, prev)) < 0x80)
-        {
-            // ASCII here, and no sequence from the block before to finish
-            prev = in;
-            block += 16;
-            continue;
-        }
-        const uint8x16_t prev1 = vextq_u8(prev, in, 15);
-        const uint8x16_t sc = vandq_u8(vandq_u8(vqtbl1q_u8(t1h, vshrq_n_u8(prev1, 4)), vqtbl1q_u8(t1l, vandq_u8(prev1, vdupq_n_u8(0x0F)))), vqtbl1q_u8(t2h, vshrq_n_u8(in, 4)));
-        const uint8x16_t must23 = vorrq_u8(vqsubq_u8(vextq_u8(prev, in, 14), vdupq_n_u8(0xE0 - 0x80)), vqsubq_u8(vextq_u8(prev, in, 13), vdupq_n_u8(0xF0 - 0x80)));
-        const uint8x16_t err = veorq_u8(vandq_u8(must23, vdupq_n_u8(0x80)), sc);
-        if (vmaxvq_u8(err) != 0)
-        {
-            break;
-        }
-        prev = in;
-        block += 16;
-    }
-#else
-    const __m128i t1h = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_1_high.data()))); // NOLINT(bugprone-casting-through-void)
-    const __m128i t1l = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_1_low.data()))); // NOLINT(bugprone-casting-through-void)
-    const __m128i t2h = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_2_high.data()))); // NOLINT(bugprone-casting-through-void)
-    const __m128i nibble = _mm_set1_epi8(0x0F);
-    const __m128i zero = _mm_setzero_si128();
-    __m128i prev = zero;
-    while (e - block >= 16)
-    {
-        const __m128i in = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(block))); // NOLINT(bugprone-casting-through-void)
-        if (_mm_movemask_epi8(_mm_or_si128(in, prev)) == 0)
-        {
-            prev = in;
-            block += 16;
-            continue;
-        }
-        const __m128i prev1 = _mm_alignr_epi8(in, prev, 15);
-        const __m128i sc = _mm_and_si128(_mm_and_si128(_mm_shuffle_epi8(t1h, _mm_and_si128(_mm_srli_epi16(prev1, 4), nibble)),
-                                         _mm_shuffle_epi8(t1l, _mm_and_si128(prev1, nibble))),
-                                         _mm_shuffle_epi8(t2h, _mm_and_si128(_mm_srli_epi16(in, 4), nibble)));
-        const __m128i must23 = _mm_or_si128(_mm_subs_epu8(_mm_alignr_epi8(in, prev, 14), _mm_set1_epi8(0xE0 - 0x80)),
-                                            _mm_subs_epu8(_mm_alignr_epi8(in, prev, 13), _mm_set1_epi8(0xF0 - 0x80)));
-        const __m128i err = _mm_xor_si128(_mm_and_si128(must23, _mm_set1_epi8(static_cast<char>(-128))), sc);
-        if (_mm_movemask_epi8(_mm_cmpeq_epi8(err, zero)) != 0xFFFF)
-        {
-            break;
-        }
-        prev = in;
-        block += 16;
-    }
-#endif
-    return block;
-}
 #endif
 
 }  // namespace detail

include/nlohmann/detail/input/string_scan.hpp

@@ -236,64 +236,6 @@ inline std::size_t valid_utf8_prefix(const unsigned char* data, std::size_t n) n
     return pos;
 }
 
-/*!
-@brief whether [data, data+n) is valid UTF-8, for checking whole strings
-
-The same answer as valid_utf8_prefix(data, n) == n. Short ASCII strings, the
-most common keys and values, are decided in one test, and long strings are
-checked 16 bytes at a time where the vector check is available.
-*/
-inline bool valid_utf8_string(const unsigned char* data, std::size_t n) noexcept
-{
-    constexpr std::uint64_t high = 0x8080808080808080ull;
-    if (n <= 16)
-    {
-        // two overlapping words cover 8 to 16 bytes, one partial word fewer
-        std::uint64_t first = 0;
-        std::uint64_t last = 0;
-        if (n >= 8)
-        {
-            std::memcpy(&first, data, sizeof(first));
-            std::memcpy(&last, data + n - 8, sizeof(last));
-        }
-        else if (n != 0)
-        {
-            std::memcpy(&first, data, n);
-        }
-        if (((first | last) & high) == 0)
-        {
-            return true;
-        }
-    }
-#if JSON_SCAN_VECTOR_UTF8
-    else if (n >= 32
-#if JSON_SCAN_SSSE3_DISPATCH
-             && cpu_has_ssse3()
-#endif
-            )
-    {
-        const unsigned char* block = vector_utf8_valid_blocks(data, data + n);
-        // the rest from the start of a sequence that may be cut at block
-        for (int i = 1; i <= 3 && block - i >= data; ++i)
-        {
-            const unsigned char c = block[-i];
-            if (c < 0x80)
-            {
-                break;
-            }
-            if (c >= 0xC0)
-            {
-                block -= i;
-                break;
-            }
-        }
-        const auto checked = static_cast<std::size_t>(block - data);
-        return checked + valid_utf8_prefix(block, n - checked) == n;
-    }
-#endif
-    return valid_utf8_prefix(data, n) == n;
-}
-
 #if JSON_SCAN_VECTOR_UTF8
 /// the end of scan_string_vector from block, where the vector loop stopped
 /// (ill-formed UTF-8, or fewer than 16 bytes left): one byte or sequence at a

include/nlohmann/detail/output/binary_writer.hpp

@@ -3080,25 +3080,6 @@ class binary_writer
         }
     }
 
-    /// write the head and the characters of @a value, at most
-    /// max_text_in_reservation of them, in one reservation
-    JSON_HEDLEY_ALWAYS_INLINE void write_cbor_string_reserved(const string_t& value)
-    {
-        CharType* const out = oa.reserve(value.size() + 2);
-        CharType* p = out;
-        if (value.size() <= 0x17)
-        {
-            *p++ = to_char_type(static_cast<std::uint8_t>(0x60 + value.size()));
-        }
-        else
-        {
-            *p++ = to_char_type(0x78);
-            *p++ = to_char_type(static_cast<std::uint8_t>(value.size()));
-        }
-        copy_characters(p, reinterpret_cast<const CharType*>(value.data()), value.size());
-        oa.commit(static_cast<std::size_t>(p - out) + value.size());
-    }
-
     /*!
     @brief write a CBOR text string
 
@@ -3120,7 +3101,19 @@ class binary_writer
             // the string is written as it is: head and characters in one reservation
             if (JSON_HEDLEY_LIKELY(value.size() <= max_text_in_reservation))
             {
-                write_cbor_string_reserved(value);
+                CharType* const out = oa.reserve(value.size() + 2);
+                CharType* p = out;
+                if (value.size() <= 0x17)
+                {
+                    *p++ = to_char_type(static_cast<std::uint8_t>(0x60 + value.size()));
+                }
+                else
+                {
+                    *p++ = to_char_type(0x78);
+                    *p++ = to_char_type(static_cast<std::uint8_t>(value.size()));
+                }
+                copy_characters(p, reinterpret_cast<const CharType*>(value.data()), value.size());
+                oa.commit(static_cast<std::size_t>(p - out) + value.size());
                 return;
             }
         }
@@ -3134,13 +3127,6 @@ class binary_writer
     JSON_HEDLEY_NEVER_INLINE
     void write_cbor_checked_string(const string_t& value, const BasicJsonType& context)
     {
-        if (error_handler == error_handler_t::strict && value.size() <= max_text_in_reservation)
-        {
-            check_utf8(value, context);
-            write_cbor_string_reserved(value);
-            return;
-        }
-
         string_t storage;
         const string_t& sanitized = sanitize_utf8_for_write(value, context, storage);
 
@@ -3155,27 +3141,6 @@ class binary_writer
     // MsgPack //
     /////////////
 
-    /// write the head and the characters of @a value, at most
-    /// max_text_in_reservation of them, in one reservation
-    JSON_HEDLEY_ALWAYS_INLINE void write_msgpack_string_reserved(const string_t& value)
-    {
-        CharType* const out = oa.reserve(value.size() + 2);
-        CharType* p = out;
-        if (value.size() <= 31)
-        {
-            // fixstr
-            *p++ = to_char_type(static_cast<std::uint8_t>(0xA0 | value.size()));
-        }
-        else
-        {
-            // str 8
-            *p++ = to_char_type(0xD9);
-            *p++ = to_char_type(static_cast<std::uint8_t>(value.size()));
-        }
-        copy_characters(p, reinterpret_cast<const CharType*>(value.data()), value.size());
-        oa.commit(static_cast<std::size_t>(p - out) + value.size());
-    }
-
     /*!
     @brief write a MessagePack str
 
@@ -3193,7 +3158,21 @@ class binary_writer
             // the string is written as it is: head and characters in one reservation
             if (JSON_HEDLEY_LIKELY(value.size() <= max_text_in_reservation))
             {
-                write_msgpack_string_reserved(value);
+                CharType* const out = oa.reserve(value.size() + 2);
+                CharType* p = out;
+                if (value.size() <= 31)
+                {
+                    // fixstr
+                    *p++ = to_char_type(static_cast<std::uint8_t>(0xA0 | value.size()));
+                }
+                else
+                {
+                    // str 8
+                    *p++ = to_char_type(0xD9);
+                    *p++ = to_char_type(static_cast<std::uint8_t>(value.size()));
+                }
+                copy_characters(p, reinterpret_cast<const CharType*>(value.data()), value.size());
+                oa.commit(static_cast<std::size_t>(p - out) + value.size());
                 return;
             }
         }
@@ -3206,13 +3185,6 @@ class binary_writer
     JSON_HEDLEY_NEVER_INLINE
     void write_msgpack_checked_string(const string_t& value, const BasicJsonType& context)
     {
-        if (error_handler == error_handler_t::strict && value.size() <= max_text_in_reservation)
-        {
-            check_utf8(value, context);
-            write_msgpack_string_reserved(value);
-            return;
-        }
-
         string_t storage;
         const string_t& sanitized = sanitize_utf8_for_write(value, context, storage);
 
@@ -4822,9 +4794,10 @@ class binary_writer
     static void check_utf8(const string_t& s, const BasicJsonType& context)
     {
         const auto* data = reinterpret_cast<const unsigned char*>(s.data());
-        if (JSON_HEDLEY_UNLIKELY(!valid_utf8_string(data, s.size())))
+        const std::size_t valid = valid_utf8_prefix(data, s.size());
+        if (JSON_HEDLEY_UNLIKELY(valid != s.size()))
         {
-            throw_invalid_utf8(data, valid_utf8_prefix(data, s.size()), context);
+            throw_invalid_utf8(data, valid, context);
         }
     }
 

single_include/nlohmann/json.hpp

@@ -12377,78 +12377,6 @@ JSON_SCAN_SSSE3_TARGET JSON_HEDLEY_NEVER_INLINE inline bool vector_utf8_run(cons
     block_out = block;
     return false;
 }
-
-/*!
-@brief skip 16-byte blocks of well-formed UTF-8 at p (a character boundary)
-
-Like vector_utf8_run, but quotes, backslashes, and control characters are
-ordinary characters. Returns the start of the first block in which the check
-found an error (which may belong to a sequence begun in the block before) or
-where fewer than 16 bytes are left; a sequence may be cut at that point, so the
-caller resumes at its start, one sequence at a time.
-*/
-JSON_SCAN_SSSE3_TARGET JSON_HEDLEY_NEVER_INLINE inline const unsigned char* vector_utf8_valid_blocks(const unsigned char* block, const unsigned char* e) noexcept
-{
-    using lookup = utf8_lookup4<>;
-#if JSON_SCAN_NEON
-    const uint8x16_t t1h = vld1q_u8(lookup::byte_1_high.data());
-    const uint8x16_t t1l = vld1q_u8(lookup::byte_1_low.data());
-    const uint8x16_t t2h = vld1q_u8(lookup::byte_2_high.data());
-    uint8x16_t prev = vdupq_n_u8(0);
-    while (e - block >= 16)
-    {
-        const uint8x16_t in = vld1q_u8(block);
-        if (vmaxvq_u8(vorrq_u8(in, prev)) < 0x80)
-        {
-            // ASCII here, and no sequence from the block before to finish
-            prev = in;
-            block += 16;
-            continue;
-        }
-        const uint8x16_t prev1 = vextq_u8(prev, in, 15);
-        const uint8x16_t sc = vandq_u8(vandq_u8(vqtbl1q_u8(t1h, vshrq_n_u8(prev1, 4)), vqtbl1q_u8(t1l, vandq_u8(prev1, vdupq_n_u8(0x0F)))), vqtbl1q_u8(t2h, vshrq_n_u8(in, 4)));
-        const uint8x16_t must23 = vorrq_u8(vqsubq_u8(vextq_u8(prev, in, 14), vdupq_n_u8(0xE0 - 0x80)), vqsubq_u8(vextq_u8(prev, in, 13), vdupq_n_u8(0xF0 - 0x80)));
-        const uint8x16_t err = veorq_u8(vandq_u8(must23, vdupq_n_u8(0x80)), sc);
-        if (vmaxvq_u8(err) != 0)
-        {
-            break;
-        }
-        prev = in;
-        block += 16;
-    }
-#else
-    const __m128i t1h = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_1_high.data()))); // NOLINT(bugprone-casting-through-void)
-    const __m128i t1l = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_1_low.data()))); // NOLINT(bugprone-casting-through-void)
-    const __m128i t2h = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_2_high.data()))); // NOLINT(bugprone-casting-through-void)
-    const __m128i nibble = _mm_set1_epi8(0x0F);
-    const __m128i zero = _mm_setzero_si128();
-    __m128i prev = zero;
-    while (e - block >= 16)
-    {
-        const __m128i in = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(block))); // NOLINT(bugprone-casting-through-void)
-        if (_mm_movemask_epi8(_mm_or_si128(in, prev)) == 0)
-        {
-            prev = in;
-            block += 16;
-            continue;
-        }
-        const __m128i prev1 = _mm_alignr_epi8(in, prev, 15);
-        const __m128i sc = _mm_and_si128(_mm_and_si128(_mm_shuffle_epi8(t1h, _mm_and_si128(_mm_srli_epi16(prev1, 4), nibble)),
-                                         _mm_shuffle_epi8(t1l, _mm_and_si128(prev1, nibble))),
-                                         _mm_shuffle_epi8(t2h, _mm_and_si128(_mm_srli_epi16(in, 4), nibble)));
-        const __m128i must23 = _mm_or_si128(_mm_subs_epu8(_mm_alignr_epi8(in, prev, 14), _mm_set1_epi8(0xE0 - 0x80)),
-                                            _mm_subs_epu8(_mm_alignr_epi8(in, prev, 13), _mm_set1_epi8(0xF0 - 0x80)));
-        const __m128i err = _mm_xor_si128(_mm_and_si128(must23, _mm_set1_epi8(static_cast<char>(-128))), sc);
-        if (_mm_movemask_epi8(_mm_cmpeq_epi8(err, zero)) != 0xFFFF)
-        {
-            break;
-        }
-        prev = in;
-        block += 16;
-    }
-#endif
-    return block;
-}
 #endif
 
 }  // namespace detail
@@ -12676,64 +12604,6 @@ inline std::size_t valid_utf8_prefix(const unsigned char* data, std::size_t n) n
     return pos;
 }
 
-/*!
-@brief whether [data, data+n) is valid UTF-8, for checking whole strings
-
-The same answer as valid_utf8_prefix(data, n) == n. Short ASCII strings, the
-most common keys and values, are decided in one test, and long strings are
-checked 16 bytes at a time where the vector check is available.
-*/
-inline bool valid_utf8_string(const unsigned char* data, std::size_t n) noexcept
-{
-    constexpr std::uint64_t high = 0x8080808080808080ull;
-    if (n <= 16)
-    {
-        // two overlapping words cover 8 to 16 bytes, one partial word fewer
-        std::uint64_t first = 0;
-        std::uint64_t last = 0;
-        if (n >= 8)
-        {
-            std::memcpy(&first, data, sizeof(first));
-            std::memcpy(&last, data + n - 8, sizeof(last));
-        }
-        else if (n != 0)
-        {
-            std::memcpy(&first, data, n);
-        }
-        if (((first | last) & high) == 0)
-        {
-            return true;
-        }
-    }
-#if JSON_SCAN_VECTOR_UTF8
-    else if (n >= 32
-#if JSON_SCAN_SSSE3_DISPATCH
-             && cpu_has_ssse3()
-#endif
-            )
-    {
-        const unsigned char* block = vector_utf8_valid_blocks(data, data + n);
-        // the rest from the start of a sequence that may be cut at block
-        for (int i = 1; i <= 3 && block - i >= data; ++i)
-        {
-            const unsigned char c = block[-i];
-            if (c < 0x80)
-            {
-                break;
-            }
-            if (c >= 0xC0)
-            {
-                block -= i;
-                break;
-            }
-        }
-        const auto checked = static_cast<std::size_t>(block - data);
-        return checked + valid_utf8_prefix(block, n - checked) == n;
-    }
-#endif
-    return valid_utf8_prefix(data, n) == n;
-}
-
 #if JSON_SCAN_VECTOR_UTF8
 /// the end of scan_string_vector from block, where the vector loop stopped
 /// (ill-formed UTF-8, or fewer than 16 bytes left): one byte or sequence at a
@@ -22199,19 +22069,6 @@ class binary_reader
         return get_bytes(len, "string", result);
     }
 
-    /// whether @a s is valid UTF-8: ASCII eight bytes at a time, the rest
-    /// sequence by sequence (as the binary writers check strings)
-    static bool is_valid_utf8_string(const string_t& s, std::true_type /*is_byte*/) noexcept
-    {
-        return valid_utf8_string(reinterpret_cast<const unsigned char*>(s.data()), s.size());
-    }
-
-    /// whether @a s, of a character type wider than a byte, is valid UTF-8
-    static bool is_valid_utf8_string(const string_t& s, std::false_type /*is_byte*/) noexcept
-    {
-        return is_valid_utf8(s);
-    }
-
     /*!
     @brief validate a decoded text string (value or object key) against @ref error_handler
 
@@ -22231,16 +22088,7 @@ class binary_reader
     */
     bool check_string_utf8(string_t& result, const char* context)
     {
-        return error_handler == error_handler_t::keep || check_string_utf8_handler(result, context);
-    }
-
-    /// @ref check_string_utf8 for an error handler other than @ref
-    /// error_handler_t::keep; out of line, so that reading strings without a
-    /// check does not pay for the code of the check
-    JSON_HEDLEY_NEVER_INLINE
-    bool check_string_utf8_handler(string_t& result, const char* context)
-    {
-        if (is_valid_utf8_string(result, std::integral_constant<bool, sizeof(typename string_t::value_type) == 1>()))
+        if (error_handler == error_handler_t::keep || is_valid_utf8(result))
         {
             return true;
         }
@@ -30458,25 +30306,6 @@ class binary_writer
         }
     }
 
-    /// write the head and the characters of @a value, at most
-    /// max_text_in_reservation of them, in one reservation
-    JSON_HEDLEY_ALWAYS_INLINE void write_cbor_string_reserved(const string_t& value)
-    {
-        CharType* const out = oa.reserve(value.size() + 2);
-        CharType* p = out;
-        if (value.size() <= 0x17)
-        {
-            *p++ = to_char_type(static_cast<std::uint8_t>(0x60 + value.size()));
-        }
-        else
-        {
-            *p++ = to_char_type(0x78);
-            *p++ = to_char_type(static_cast<std::uint8_t>(value.size()));
-        }
-        copy_characters(p, reinterpret_cast<const CharType*>(value.data()), value.size());
-        oa.commit(static_cast<std::size_t>(p - out) + value.size());
-    }
-
     /*!
     @brief write a CBOR text string
 
@@ -30498,7 +30327,19 @@ class binary_writer
             // the string is written as it is: head and characters in one reservation
             if (JSON_HEDLEY_LIKELY(value.size() <= max_text_in_reservation))
             {
-                write_cbor_string_reserved(value);
+                CharType* const out = oa.reserve(value.size() + 2);
+                CharType* p = out;
+                if (value.size() <= 0x17)
+                {
+                    *p++ = to_char_type(static_cast<std::uint8_t>(0x60 + value.size()));
+                }
+                else
+                {
+                    *p++ = to_char_type(0x78);
+                    *p++ = to_char_type(static_cast<std::uint8_t>(value.size()));
+                }
+                copy_characters(p, reinterpret_cast<const CharType*>(value.data()), value.size());
+                oa.commit(static_cast<std::size_t>(p - out) + value.size());
                 return;
             }
         }
@@ -30512,13 +30353,6 @@ class binary_writer
     JSON_HEDLEY_NEVER_INLINE
     void write_cbor_checked_string(const string_t& value, const BasicJsonType& context)
     {
-        if (error_handler == error_handler_t::strict && value.size() <= max_text_in_reservation)
-        {
-            check_utf8(value, context);
-            write_cbor_string_reserved(value);
-            return;
-        }
-
         string_t storage;
         const string_t& sanitized = sanitize_utf8_for_write(value, context, storage);
 
@@ -30533,27 +30367,6 @@ class binary_writer
     // MsgPack //
     /////////////
 
-    /// write the head and the characters of @a value, at most
-    /// max_text_in_reservation of them, in one reservation
-    JSON_HEDLEY_ALWAYS_INLINE void write_msgpack_string_reserved(const string_t& value)
-    {
-        CharType* const out = oa.reserve(value.size() + 2);
-        CharType* p = out;
-        if (value.size() <= 31)
-        {
-            // fixstr
-            *p++ = to_char_type(static_cast<std::uint8_t>(0xA0 | value.size()));
-        }
-        else
-        {
-            // str 8
-            *p++ = to_char_type(0xD9);
-            *p++ = to_char_type(static_cast<std::uint8_t>(value.size()));
-        }
-        copy_characters(p, reinterpret_cast<const CharType*>(value.data()), value.size());
-        oa.commit(static_cast<std::size_t>(p - out) + value.size());
-    }
-
     /*!
     @brief write a MessagePack str
 
@@ -30571,7 +30384,21 @@ class binary_writer
             // the string is written as it is: head and characters in one reservation
             if (JSON_HEDLEY_LIKELY(value.size() <= max_text_in_reservation))
             {
-                write_msgpack_string_reserved(value);
+                CharType* const out = oa.reserve(value.size() + 2);
+                CharType* p = out;
+                if (value.size() <= 31)
+                {
+                    // fixstr
+                    *p++ = to_char_type(static_cast<std::uint8_t>(0xA0 | value.size()));
+                }
+                else
+                {
+                    // str 8
+                    *p++ = to_char_type(0xD9);
+                    *p++ = to_char_type(static_cast<std::uint8_t>(value.size()));
+                }
+                copy_characters(p, reinterpret_cast<const CharType*>(value.data()), value.size());
+                oa.commit(static_cast<std::size_t>(p - out) + value.size());
                 return;
             }
         }
@@ -30584,13 +30411,6 @@ class binary_writer
     JSON_HEDLEY_NEVER_INLINE
     void write_msgpack_checked_string(const string_t& value, const BasicJsonType& context)
     {
-        if (error_handler == error_handler_t::strict && value.size() <= max_text_in_reservation)
-        {
-            check_utf8(value, context);
-            write_msgpack_string_reserved(value);
-            return;
-        }
-
         string_t storage;
         const string_t& sanitized = sanitize_utf8_for_write(value, context, storage);
 
@@ -32200,9 +32020,10 @@ class binary_writer
     static void check_utf8(const string_t& s, const BasicJsonType& context)
     {
         const auto* data = reinterpret_cast<const unsigned char*>(s.data());
-        if (JSON_HEDLEY_UNLIKELY(!valid_utf8_string(data, s.size())))
+        const std::size_t valid = valid_utf8_prefix(data, s.size());
+        if (JSON_HEDLEY_UNLIKELY(valid != s.size()))
         {
-            throw_invalid_utf8(data, valid_utf8_prefix(data, s.size()), context);
+            throw_invalid_utf8(data, valid, context);
         }
     }
 

tests/src/unit-guard-page.cpp

@@ -403,7 +403,6 @@ TEST_CASE("guard page")
                     CHECK(nlohmann::detail::find_string_special(p, n) <= n);
                     CHECK(nlohmann::detail::find_ascii_copyable_run(p, n) <= n);
                     CHECK(nlohmann::detail::valid_utf8_prefix(p, n) <= n);
-                    CHECK(nlohmann::detail::valid_utf8_string(p, n) == (nlohmann::detail::valid_utf8_prefix(p, n) == n));
 #if defined(JSON_USE_SIMDUTF) && defined(JSON_HAS_CPP_17)
                     CHECK(nlohmann::detail::find_string_delimiter(p, n) <= n);
 #endif

tests/src/unit-json_view_from_json.cpp

@@ -39,6 +39,7 @@ using nlohmann::ordered_json_document;
 
 #ifdef JSON_HAS_CPP_17
     #include <optional>
+    #include <string_view>
 #endif
 
 // NLOHMANN_JSON_SERIALIZE_ENUM uses a static std::pair; same() compares floating-point values on purpose
@@ -469,5 +470,70 @@ TEST_CASE("json_view from_json")
 #endif
 }
 
+#ifdef JSON_HAS_CPP_17
+namespace view_from_json
+{
+// a string_view member is not copied: it points into the source text or, for a
+// string with escape sequences, into the buffer of decoded strings of the document
+struct named_view
+{
+    // initialized for GCC -Weffc++
+    // NOLINTNEXTLINE(readability-redundant-member-init)
+    std::string_view name{};
+    int n = 0;
+    NLOHMANN_DEFINE_TYPE_INTRUSIVE(named_view, name, n)
+};
+}  // namespace view_from_json
+
+TEST_CASE("json_view from_json: string_view members borrow from the document")
+{
+    using view_from_json::named_view;
+
+    // whether all of s is inside the bytes of text
+    const auto within = [](std::string_view s, std::string_view text)
+    {
+        const auto first = reinterpret_cast<std::uintptr_t>(text.data());
+        const auto begin = reinterpret_cast<std::uintptr_t>(s.data());
+        return begin >= first && begin + s.size() <= first + text.size();
+    };
+
+    SECTION("a string without escapes points into the source text")
+    {
+        const std::string text = R"({"name": "hello", "n": 1})";
+        const json_document d = json_document::parse(text);
+        REQUIRE_FALSE(d.owns_source());
+        const auto r = d.root().get<named_view>();
+        CHECK(r.name == "hello");
+        CHECK(r.n == 1);
+        CHECK(within(r.name, text));
+        CHECK(within(r.name, d.source()));
+    }
+
+    SECTION("a string with escapes points into the document, not into the source text")
+    {
+        const std::string text = R"({"name": "a\nb", "n": 2})";
+        json_document d = json_document::parse(text);
+        REQUIRE_FALSE(d.owns_source());
+        const auto r = d.root().get<named_view>();
+        CHECK(r.name == "a\nb");
+        CHECK(r.n == 2);
+        CHECK_FALSE(within(r.name, text));
+        // valid as long as the document is alive, even if the document is moved
+        const json_document moved = std::move(d);
+        CHECK(r.name == "a\nb");
+        CHECK(moved.root().get<named_view>().name == r.name);
+    }
+
+    SECTION("a document that owns its text keeps the members readable while it is alive")
+    {
+        const json_document d = json_document::parse(std::string(R"({"name": "owned", "n": 3})"));
+        REQUIRE(d.owns_source());
+        const auto r = d.root().get<named_view>();
+        CHECK(r.name == "owned");
+        CHECK(within(r.name, d.source()));
+    }
+}
+#endif
+
 DOCTEST_CLANG_SUPPRESS_WARNING_POP
 DOCTEST_GCC_SUPPRESS_WARNING_POP

tests/src/unit-unicode.cpp

@@ -13,7 +13,6 @@ using nlohmann::json;
 
 #include <algorithm>
 #include <fstream>
-#include <random>
 #include <string>
 #include "make_test_data_available.hpp"
 #include "test_utils.hpp"
@@ -1632,40 +1631,3 @@ TEST_CASE("Unicode RFC 3629")
 }
 
 DOCTEST_CLANG_SUPPRESS_WARNING_POP
-
-TEST_CASE("UTF-8 check of whole strings")
-{
-    // valid_utf8_string() decides short strings with a word test and long ones
-    // 16 bytes at a time where a vector check is available; it must agree with
-    // the byte-wise check for every mix of ASCII, sequences of each length,
-    // ill-formed and truncated sequences, at every length and offset
-    const char* const pieces[] =
-    {
-        "a", "\x7F", "\xC3\xA9", "\xE2\x82\xAC", "\xE0\xA0\x80", "\xEF\xBF\xBF", "\xF0\x9F\x98\x80", "\xF4\x8F\xBF\xBF",
-        "\x80", "\xC0\xAF", "\xC3", "\xE2\x82", "\xED\xA0\x80", "\xF0\x9F", "\xF4\x90\x80\x80", "\xFF"
-    };
-    // std::mt19937's sequence is fixed by the standard; no distribution is used
-    std::mt19937 rng(5);
-    std::size_t valid = 0;
-    for (int i = 0; i < 100000; ++i)
-    {
-        std::string s;
-        const std::size_t length = rng() % 100;
-        const std::uint32_t ascii = rng() % 101;
-        while (s.size() < length)
-        {
-            // mostly well-formed pieces (the first eight), so that long valid
-            // strings are common
-            s += (rng() % 100 < ascii) ? std::string("x") : std::string(pieces[rng() % (rng() % 8 == 0 ? 16 : 8)]);
-        }
-        const auto* data = reinterpret_cast<const unsigned char*>(s.data());
-        const bool expected = nlohmann::detail::is_valid_utf8(s);
-        valid += expected ? 1 : 0;
-        CAPTURE(s)
-        CHECK(nlohmann::detail::valid_utf8_string(data, s.size()) == expected);
-        CHECK((nlohmann::detail::valid_utf8_prefix(data, s.size()) == s.size()) == expected);
-    }
-    // both outcomes are common enough to be tested
-    CHECK(valid > 20000);
-    CHECK(valid < 80000);
-}