Fix clang-tidy findings in the accept() string test

Use raw string literals and append instead of operator+ chains to fix
ci_clang_tidy (modernize-raw-string-literal,
performance-inefficient-string-concatenation) in unit-class_parser.cpp.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

include/nlohmann/detail/input/binary_reader.hpp

@@ -741,13 +741,11 @@ class binary_reader
     bool get_cbor_negative_integer()
     {
         NumberType number{};
-        return get_number(number) && emit_cbor_negative_integer(number);
+        if (JSON_HEDLEY_UNLIKELY(!get_number(number)))
-    }
+        {
+            return false;
+        }
 
-    /// pass the CBOR negative integer -1 - @a number to the SAX parser
-    template<typename NumberType>
-    bool emit_cbor_negative_integer(const NumberType number)
-    {
         // the value is -1 - number, which fits into number_integer_t
         // whenever number does; the outer cast undoes the integral promotion
         // for number_integer_t types narrower than int
@@ -972,7 +970,7 @@ class binary_reader
             case 0x95:
             case 0x96:
             case 0x97:
-                return enter_cbor_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu));
+                return enter_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu));
 
             case 0x98: // array (one-byte uint8_t for n follows)
             case 0x99: // array (two-byte uint16_t for n follow)
@@ -981,7 +979,7 @@ class binary_reader
             {
                 std::uint64_t len{};
                 std::size_t size{};
-                return get_cbor_argument(len) && get_cbor_container_size(len, size, "array") && enter_cbor_array(size);
+                return get_cbor_argument(len) && get_cbor_container_size(len, size, "array") && enter_array(size);
             }
 
             case 0x9F: // array (indefinite length)
@@ -1678,181 +1676,6 @@ class binary_reader
         return true;
     }
 
-    /*!
-    @brief read a big-endian number of type @a NumberType at @a data
-    */
-    template<typename NumberType>
-    NumberType load_big_endian(const unsigned char* data) const noexcept
-    {
-        NumberType result{};
-        std::memcpy(&result, data, sizeof(NumberType));
-        if (is_little_endian)
-        {
-            byte_swap(result);
-        }
-        return result;
-    }
-
-    /*!
-    @brief read the integers, floats, booleans, and nulls that follow in a
-           definite-length array, without the per-element bookkeeping of
-           @ref parse_cbor_internal
-
-    Stops at the end of the array, at any other kind of value, and when fewer
-    than 9 bytes (the longest of these values) are left in the input, leaving
-    those to @ref parse_cbor_value, which reads them the same way.
-
-    The caller has checked that an element remains, that at least 9 bytes are
-    left, and that the next byte begins a scalar.
-
-    @param[in,out] remaining  the number of elements of the array not yet read
-    @return whether the SAX parser accepted the values
-    */
-    bool parse_cbor_scalar_run(std::size_t& remaining)
-    {
-        do
-        {
-            const auto* const data = reinterpret_cast<const unsigned char*>(ia.bulk_data());
-            const unsigned char head = data[0];
-            std::size_t size = 0;
-            bool accepted = true;
-            switch (head)
-            {
-                case 0x18:
-                    size = 2;
-                    accepted = emit_unsigned(data[1]);
-                    break;
-                case 0x19:
-                    size = 3;
-                    accepted = emit_unsigned(load_big_endian<std::uint16_t>(data + 1));
-                    break;
-                case 0x1A:
-                    size = 5;
-                    accepted = emit_unsigned(load_big_endian<std::uint32_t>(data + 1));
-                    break;
-                case 0x1B:
-                    size = 9;
-                    accepted = emit_unsigned(load_big_endian<std::uint64_t>(data + 1));
-                    break;
-                case 0x38:
-                    size = 2;
-                    accepted = emit_cbor_negative_integer(data[1]);
-                    break;
-                case 0x39:
-                    size = 3;
-                    accepted = emit_cbor_negative_integer(load_big_endian<std::uint16_t>(data + 1));
-                    break;
-                case 0x3A:
-                    size = 5;
-                    accepted = emit_cbor_negative_integer(load_big_endian<std::uint32_t>(data + 1));
-                    break;
-                case 0x3B:
-                    size = 9;
-                    accepted = emit_cbor_negative_integer(load_big_endian<std::uint64_t>(data + 1));
-                    break;
-                case 0xF4:
-                    size = 1;
-                    accepted = sax->boolean(false);
-                    break;
-                case 0xF5:
-                    size = 1;
-                    accepted = sax->boolean(true);
-                    break;
-                case 0xF6:
-                    size = 1;
-                    accepted = sax->null();
-                    break;
-                case 0xFA:
-                    size = 5;
-                    accepted = emit_float(load_big_endian<float>(data + 1));
-                    break;
-                case 0xFB:
-                    size = 9;
-                    accepted = emit_float(load_big_endian<double>(data + 1));
-                    break;
-                default:
-                    if (head <= 0x17)
-                    {
-                        size = 1;
-                        accepted = sax->number_unsigned(static_cast<number_unsigned_t>(head));
-                    }
-                    else if (head >= 0x20 && head <= 0x37)
-                    {
-                        size = 1;
-                        accepted = sax->number_integer(static_cast<std::int8_t>(0x20 - 1 - head));
-                    }
-                    else
-                    {
-                        // any other value is read by parse_cbor_value
-                        return true;
-                    }
-                    break;
-            }
-            // as if read by get() and get_number(): current is the head byte
-            ia.bulk_skip(size);
-            chars_read += size;
-            current = head;
-            --remaining;
-            if (JSON_HEDLEY_UNLIKELY(!accepted))
-            {
-                return false;
-            }
-        }
-        while (remaining != 0 && ia.bulk_remaining() >= 9);
-        return true;
-    }
-
-    /*!
-    @brief open a definite-length array and read the scalars it begins with
-           (see @ref parse_cbor_scalar_run)
-
-    Only the start of an array is tried, which covers arrays of numbers
-    (e.g. coordinates) but costs arrays of other values only one test, not one
-    per element.
-
-    @param[in] len  the number of elements
-    @return whether the SAX parser accepted the array and the values read
-    */
-    bool enter_cbor_array(const std::size_t len)
-    {
-        return enter_array(len) && (len == 0 || !cbor_scalar_follows(std::integral_constant<bool, bulk_scan> {})
-                                    || parse_cbor_array_start(std::integral_constant<bool, bulk_scan> {}));
-    }
-
-    /// whether a run of scalars can start at the next byte: at least 9 bytes
-    /// are left and the byte begins an integer, a float, a boolean, or null;
-    /// one test, so that an array of containers or strings makes no call
-    bool cbor_scalar_follows(std::true_type /*bulk*/) const
-    {
-        if (ia.bulk_remaining() < 9)
-        {
-            return false;
-        }
-        const auto head = static_cast<unsigned char>(*ia.bulk_data());
-        return head < 0x40 || head >= 0xF4;
-    }
-
-    /// input that is not contiguous: every value is read by parse_cbor_value
-    bool cbor_scalar_follows(std::false_type /*bulk*/) const noexcept
-    {
-        return false;
-    }
-
-    /// read the scalars the array just opened begins with; out of line, so
-    /// that @ref parse_cbor_value stays small enough to be inlined into
-    /// @ref parse_cbor_internal
-    JSON_HEDLEY_NEVER_INLINE
-    bool parse_cbor_array_start(std::true_type /*bulk*/)
-    {
-        return parse_cbor_scalar_run(container_stack.back().remaining);
-    }
-
-    /// input that is not contiguous: every value is read by parse_cbor_value
-    bool parse_cbor_array_start(std::false_type /*bulk*/) const noexcept
-    {
-        return true;
-    }
-
     /*!
     @brief read a CBOR value and everything nested inside it
 
@@ -1882,7 +1705,6 @@ class binary_reader
                 // pop_back() below, which destroys the container_stack element
                 // it would otherwise alias
                 const container_frame top = container_stack.back();
-                const bool is_object = top.is_object;
                 bool at_end = false;
 
                 if (top.remaining != npos)
@@ -1894,7 +1716,7 @@ class binary_reader
                     {
                         // claim the element about to be read
                         --container_stack.back().remaining;
-                        if (is_object)
+                        if (top.is_object)
                         {
                             get();
                         }
@@ -1907,7 +1729,7 @@ class binary_reader
                     // Testing for it consumes a byte, which is the first byte
                     // of the next element when it is not one.
                     at_end = (get() == 0xFF);
-                    fetch = is_object;
+                    fetch = top.is_object;
                 }
 
                 if (at_end)
@@ -1924,7 +1746,7 @@ class binary_reader
                     continue;
                 }
 
-                if (is_object)
+                if (top.is_object)
                 {
                     if (JSON_HEDLEY_UNLIKELY(!skip_cbor_key_tags(tag_handler)))
                     {
@@ -3869,13 +3691,13 @@ class binary_reader
                 return sax->null();
 
             case 0xFB:
-                return sax->number_float(static_cast<number_float_t>(-1.0), no_source);
+                return sax->number_float(static_cast<number_float_t>(-1.0), "");
 
             case 0xFC:
-                return sax->number_float(static_cast<number_float_t>(0.0), no_source);
+                return sax->number_float(static_cast<number_float_t>(0.0), "");
 
             case 0xFD:
-                return sax->number_float(static_cast<number_float_t>(1.0), no_source);
+                return sax->number_float(static_cast<number_float_t>(1.0), "");
 
             case 0xFF: // empty string
             {
@@ -4379,7 +4201,7 @@ class binary_reader
         {
             return out_of_range_error(exception_id::number_overflow, "number overflow", "value");
         }
-        return sax->number_float(result, no_source);
+        return sax->number_float(result, "");
     }
 
     /*!
@@ -4439,7 +4261,7 @@ class binary_reader
         }();
         return sax->number_float((half & 0x8000u) != 0
                                  ? static_cast<number_float_t>(-val)
-                                 : static_cast<number_float_t>(val), no_source);
+                                 : static_cast<number_float_t>(val), "");
     }
 
     /*!
@@ -4764,10 +4586,6 @@ class binary_reader
     /// the SAX parser
     json_sax_t* sax = nullptr;
 
-    /// the (empty) source text of every number_float event: binary formats
-    /// have none, and a string_t built for each float would cost more
-    const string_t no_source{};
-
     /// the containers that have been opened and not closed yet; see @ref container_frame
     std::vector<container_frame> container_stack{};
 

include/nlohmann/detail/input/lexer.hpp

@@ -268,10 +268,10 @@ class lexer : public lexer_base<BasicJsonType>
   public:
     using token_type = typename lexer_base<BasicJsonType>::token_type;
 
-    explicit lexer(InputAdapterType&& adapter, bool ignore_comments_ = false, bool discard_number_values_ = false) noexcept
+    explicit lexer(InputAdapterType&& adapter, bool ignore_comments_ = false, bool discard_values_ = false) noexcept
         : ia(std::move(adapter))
         , ignore_comments(ignore_comments_)
-        , discard_number_values(discard_number_values_)
+        , discard_values(discard_values_)
     {
         // the token string of an error before the first token is everything
         // read so far
@@ -388,6 +388,8 @@ class lexer : public lexer_base<BasicJsonType>
     checks if it is inside the range. If a violation was detected, set up an
     error message and return false. Otherwise, return true.
 
+    @param[in] keep    whether the bytes are added to token_buffer (false for
+                       accept(), see scan())
     @param[in] ranges  list of integers; interpreted as list of pairs of
                        inclusive lower and upper bound, respectively
 
@@ -396,17 +398,18 @@ class lexer : public lexer_base<BasicJsonType>
 
     @return true if and only if no range violation was detected
     */
-    bool next_byte_in_range(std::initializer_list<char_int_type> ranges)
+    template<bool Keep>
+    bool next_byte_in_range(std::integral_constant<bool, Keep> keep, std::initializer_list<char_int_type> ranges)
     {
         JSON_ASSERT(ranges.size() == 2 || ranges.size() == 4 || ranges.size() == 6);
-        add(current);
+        add_string_char(keep, current);
 
         for (auto range = ranges.begin(); range != ranges.end(); ++range)
         {
             get();
             if (JSON_HEDLEY_LIKELY(*range <= current && current <= *(++range))) // NOLINT(bugprone-inc-dec-in-conditions)
             {
-                add(current);
+                add_string_char(keep, current);
             }
             else
             {
@@ -419,14 +422,16 @@ class lexer : public lexer_base<BasicJsonType>
     }
 
     /// contiguous input: bulk-append the run of ordinary characters and complete
-    /// well-formed UTF-8 sequences starting at the current read position, then
+    /// well-formed UTF-8 sequences starting at the current read position (only
+    /// skip it if @a keep is false), then
     /// read the first byte that needs individual handling (the closing quote, an
     /// escape, a control character, or an ill-formed UTF-8 byte) like get().
     /// That byte is taken from the buffer that was just scanned. Through get(),
     /// Apple Clang merged this read with the other get() calls of the scan
     /// function, which load the read position again right after it was stored
     /// (3% of json::accept() on jeopardy.json on Apple M1).
-    char_int_type get_after_string_run(std::true_type /*bulk*/)
+    template<bool Keep>
+    char_int_type get_after_string_run(std::true_type /*bulk*/, std::integral_constant<bool, Keep> keep)
     {
         // a pending unget must be consumed through the normal path first
         if (next_unget)
@@ -444,7 +449,7 @@ class lexer : public lexer_base<BasicJsonType>
         const std::size_t pos = lexer_string_bulk_run(data, remaining);
         if (pos != 0)
         {
-            token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(data), pos);
+            append_string_run(keep, data, pos);
             bulk_consume(reinterpret_cast<const char*>(data), pos);
         }
         if (pos == remaining)
@@ -488,7 +493,8 @@ class lexer : public lexer_base<BasicJsonType>
     }
 
     /// streaming input: no bulk fast path
-    char_int_type get_after_string_run(std::false_type /*bulk*/)
+    template<bool Keep>
+    char_int_type get_after_string_run(std::false_type /*bulk*/, std::integral_constant<bool, Keep> /*keep*/)
     {
         return get();
     }
@@ -502,13 +508,18 @@ class lexer : public lexer_base<BasicJsonType>
     may contain \0 bytes), and token_buffer.size() is the number of bytes in the
     string.
 
+    @param[in] keep  whether the string is copied into token_buffer; if false
+                     (accept(), see scan()), it is only checked, with the same
+                     errors, and token_buffer stays empty
+
     @return token_type::value_string if string could be successfully scanned,
             token_type::parse_error otherwise
 
     @note In case of errors, variable error_message contains a textual
           description.
     */
-    token_type scan_string()
+    template<bool Keep>
+    token_type scan_string(std::integral_constant<bool, Keep> keep)
     {
         // reset token_buffer (ignore opening quote)
         reset();
@@ -520,7 +531,7 @@ class lexer : public lexer_base<BasicJsonType>
         {
             // bulk-consume ordinary characters from contiguous input, then
             // get the next character, the one that ends the run
-            switch (get_after_string_run(std::integral_constant<bool, bulk_scan>()))
+            switch (get_after_string_run(std::integral_constant<bool, bulk_scan>(), keep))
             {
                 // end of file while parsing the string
                 case char_traits<char_type>::eof():
@@ -542,35 +553,35 @@ class lexer : public lexer_base<BasicJsonType>
                     {
                         // quotation mark
                         case '\"':
-                            add('\"');
+                            add_string_char(keep, '\"');
                             break;
                         // reverse solidus
                         case '\\':
-                            add('\\');
+                            add_string_char(keep, '\\');
                             break;
                         // solidus
                         case '/':
-                            add('/');
+                            add_string_char(keep, '/');
                             break;
                         // backspace
                         case 'b':
-                            add('\b');
+                            add_string_char(keep, '\b');
                             break;
                         // form feed
                         case 'f':
-                            add('\f');
+                            add_string_char(keep, '\f');
                             break;
                         // line feed
                         case 'n':
-                            add('\n');
+                            add_string_char(keep, '\n');
                             break;
                         // carriage return
                         case 'r':
-                            add('\r');
+                            add_string_char(keep, '\r');
                             break;
                         // tab
                         case 't':
-                            add('\t');
+                            add_string_char(keep, '\t');
                             break;
 
                         // unicode escapes
@@ -638,10 +649,7 @@ class lexer : public lexer_base<BasicJsonType>
                             JSON_ASSERT(0x00 <= codepoint && codepoint <= 0x10FFFF);
 
                             // translate codepoint into bytes
-                            encode_utf8(static_cast<std::uint32_t>(codepoint), [this](std::uint32_t byte)
+                            add_codepoint(keep, codepoint);
-                            {
-                                add(static_cast<char_int_type>(byte));
-                            });
 
                             break;
                         }
@@ -824,7 +832,7 @@ class lexer : public lexer_base<BasicJsonType>
                 case 0x7E:
                 case 0x7F:
                 {
-                    add(current);
+                    add_string_char(keep, current);
                     break;
                 }
 
@@ -860,7 +868,7 @@ class lexer : public lexer_base<BasicJsonType>
                 case 0xDE:
                 case 0xDF:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!next_byte_in_range({0x80, 0xBF})))
+                    if (JSON_HEDLEY_UNLIKELY(!next_byte_in_range(keep, {0x80, 0xBF})))
                     {
                         return token_type::parse_error;
                     }
@@ -870,7 +878,7 @@ class lexer : public lexer_base<BasicJsonType>
                 // U+0800..U+0FFF: bytes E0 A0..BF 80..BF
                 case 0xE0:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0xA0, 0xBF, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0xA0, 0xBF, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -894,7 +902,7 @@ class lexer : public lexer_base<BasicJsonType>
                 case 0xEE:
                 case 0xEF:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0x80, 0xBF, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0x80, 0xBF, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -904,7 +912,7 @@ class lexer : public lexer_base<BasicJsonType>
                 // U+D000..U+D7FF: bytes ED 80..9F 80..BF
                 case 0xED:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0x80, 0x9F, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0x80, 0x9F, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -914,7 +922,7 @@ class lexer : public lexer_base<BasicJsonType>
                 // U+10000..U+3FFFF F0 90..BF 80..BF 80..BF
                 case 0xF0:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0x90, 0xBF, 0x80, 0xBF, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0x90, 0xBF, 0x80, 0xBF, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -926,7 +934,7 @@ class lexer : public lexer_base<BasicJsonType>
                 case 0xF2:
                 case 0xF3:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0x80, 0xBF, 0x80, 0xBF, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0x80, 0xBF, 0x80, 0xBF, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -936,7 +944,7 @@ class lexer : public lexer_base<BasicJsonType>
                 // U+100000..U+10FFFF F4 80..8F 80..BF 80..BF
                 case 0xF4:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0x80, 0x8F, 0x80, 0xBF, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0x80, 0x8F, 0x80, 0xBF, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -1427,7 +1435,7 @@ scan_number_done:
     token_type convert_number(token_type number_type, std::size_t mantissa_end)
     {
         // accept() only needs to know whether the input is valid, so it sets
-        // discard_number_values (see json.hpp), and an integer token whose
+        // discard_values (see json.hpp), and an integer token whose
         // digit count shows that it fits is reported without calling
         // convert_integer(). A number with up to 18 digits always fits into
         // both std::uint64_t and std::int64_t (18 nines is about 1e18, below
@@ -1442,7 +1450,7 @@ scan_number_done:
         // json_sax_acceptor, whose number callbacks discard their argument and
         // return true, and the parser rejects neither integers nor finite
         // floats. value_unsigned/value_integer are left unset here, so a caller
-        // that reads the converted value must not set discard_number_values.
+        // that reads the converted value must not set discard_values.
         //
         // On contiguous input, scan_number_bulk_contiguous() converts integer
         // tokens itself and does not pass them to this function, unless
@@ -1450,7 +1458,7 @@ scan_number_done:
         // reached for input without bulk access (e.g. streams), with
         // JSON_DIAGNOSTIC_POSITIONS, or when scan_number_bulk_contiguous()
         // falls back to scan_number().
-        if (discard_number_values)
+        if (discard_values)
         {
             constexpr std::size_t safe_digit_count = 18;
             if (number_type == token_type::value_unsigned && token_buffer.size() <= safe_digit_count)
@@ -1701,7 +1709,7 @@ scan_number_done:
         // w < 10^19, so a value below 10^max_exponent10 cannot overflow, and a
         // value that underflows is a finite number as well. Only a token that
         // may overflow has to be converted to find out.
-        if (JSON_HEDLEY_UNLIKELY(discard_number_values && s.exponent + 19 <= std::numeric_limits<number_float_t>::max_exponent10))
+        if (JSON_HEDLEY_UNLIKELY(discard_values && s.exponent + 19 <= std::numeric_limits<number_float_t>::max_exponent10))
         {
             value_float = 0;
             return true;
@@ -2033,6 +2041,34 @@ scan_number_done:
         token_buffer.push_back(static_cast<typename string_t::value_type>(c));
     }
 
+    /// add a character of a string token; accept() checks the string but does
+    /// not keep its value (@a keep is false)
+    void add_string_char(std::true_type /*keep*/, char_int_type c)
+    {
+        token_buffer.push_back(static_cast<typename string_t::value_type>(c));
+    }
+
+    static void add_string_char(std::false_type /*keep*/, char_int_type /*c*/) noexcept {}
+
+    /// add the UTF-8 bytes of a code point from a \\u escape to a string token
+    void add_codepoint(std::true_type /*keep*/, int codepoint)
+    {
+        encode_utf8(static_cast<std::uint32_t>(codepoint), [this](std::uint32_t byte)
+        {
+            add(static_cast<char_int_type>(byte));
+        });
+    }
+
+    static void add_codepoint(std::false_type /*keep*/, int /*codepoint*/) noexcept {}
+
+    /// append a run of ordinary string characters (see get_after_string_run())
+    void append_string_run(std::true_type /*keep*/, const unsigned char* data, std::size_t n)
+    {
+        token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(data), n);
+    }
+
+    static void append_string_run(std::false_type /*keep*/, const unsigned char* /*data*/, std::size_t /*n*/) noexcept {}
+
   public:
     /////////////////////
     // value getters
@@ -2427,7 +2463,11 @@ scan_number_done:
 
             // string
             case '\"':
-                return scan_string();
+                // accept() (discard_values) checks strings without copying them
+                // into token_buffer. The choice is made once per string: a
+                // check inside the string loop made number-heavy documents up
+                // to 3 % slower (mesh.json, Apple M1)
+                return discard_values ? scan_string(std::false_type {}) : scan_string(std::true_type {});
 
             // number
             case '-':
@@ -2512,11 +2552,13 @@ scan_number_done:
     std::size_t decimal_point_position = std::string::npos;
 
     /// whether the caller only needs the token types and never looks at the
-    /// converted numeric values; set only by accept(), which parses through
+    /// values of number and string tokens; set only by accept(), which parses
-    /// json_sax_acceptor. When set, convert_number() skips converting integer
+    /// through json_sax_acceptor. When set, convert_number() skips converting
-    /// tokens whose digit count guarantees that they fit into 64 bits (see
+    /// integer tokens whose digit count guarantees that they fit into 64 bits
-    /// there)
+    /// (see there), floats are converted only when they may overflow (see
-    const bool discard_number_values = false;
+    /// convert_accumulated_float()), and strings are checked without being
+    /// copied into token_buffer (see scan())
+    const bool discard_values = false;
 };
 
 }  // namespace detail

include/nlohmann/detail/input/parser.hpp

@@ -89,9 +89,9 @@ class parser
                     const bool allow_exceptions_ = true,
                     const bool ignore_comments = false,
                     const bool ignore_trailing_commas_ = false,
-                    const bool discard_number_values_ = false)
+                    const bool discard_values_ = false)
         : callback(std::move(cb))
-        , m_lexer(std::move(adapter), ignore_comments, discard_number_values_)
+        , m_lexer(std::move(adapter), ignore_comments, discard_values_)
         , allow_exceptions(allow_exceptions_)
         , ignore_trailing_commas(ignore_trailing_commas_)
     {

include/nlohmann/json.hpp

@@ -184,11 +184,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         const bool allow_exceptions = true,
         const bool ignore_comments = false,
         const bool ignore_trailing_commas = false,
-        const bool discard_number_values = false
+        const bool discard_values = false
     )
     {
         return ::nlohmann::detail::parser<basic_json, InputAdapterType>(std::move(adapter),
-               std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas, discard_number_values);
+               std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas, discard_values);
     }
 
   private:

single_include/nlohmann/json.hpp

@@ -13124,10 +13124,10 @@ class lexer : public lexer_base<BasicJsonType>
   public:
     using token_type = typename lexer_base<BasicJsonType>::token_type;
 
-    explicit lexer(InputAdapterType&& adapter, bool ignore_comments_ = false, bool discard_number_values_ = false) noexcept
+    explicit lexer(InputAdapterType&& adapter, bool ignore_comments_ = false, bool discard_values_ = false) noexcept
         : ia(std::move(adapter))
         , ignore_comments(ignore_comments_)
-        , discard_number_values(discard_number_values_)
+        , discard_values(discard_values_)
     {
         // the token string of an error before the first token is everything
         // read so far
@@ -13244,6 +13244,8 @@ class lexer : public lexer_base<BasicJsonType>
     checks if it is inside the range. If a violation was detected, set up an
     error message and return false. Otherwise, return true.
 
+    @param[in] keep    whether the bytes are added to token_buffer (false for
+                       accept(), see scan())
     @param[in] ranges  list of integers; interpreted as list of pairs of
                        inclusive lower and upper bound, respectively
 
@@ -13252,17 +13254,18 @@ class lexer : public lexer_base<BasicJsonType>
 
     @return true if and only if no range violation was detected
     */
-    bool next_byte_in_range(std::initializer_list<char_int_type> ranges)
+    template<bool Keep>
+    bool next_byte_in_range(std::integral_constant<bool, Keep> keep, std::initializer_list<char_int_type> ranges)
     {
         JSON_ASSERT(ranges.size() == 2 || ranges.size() == 4 || ranges.size() == 6);
-        add(current);
+        add_string_char(keep, current);
 
         for (auto range = ranges.begin(); range != ranges.end(); ++range)
         {
             get();
             if (JSON_HEDLEY_LIKELY(*range <= current && current <= *(++range))) // NOLINT(bugprone-inc-dec-in-conditions)
             {
-                add(current);
+                add_string_char(keep, current);
             }
             else
             {
@@ -13275,14 +13278,16 @@ class lexer : public lexer_base<BasicJsonType>
     }
 
     /// contiguous input: bulk-append the run of ordinary characters and complete
-    /// well-formed UTF-8 sequences starting at the current read position, then
+    /// well-formed UTF-8 sequences starting at the current read position (only
+    /// skip it if @a keep is false), then
     /// read the first byte that needs individual handling (the closing quote, an
     /// escape, a control character, or an ill-formed UTF-8 byte) like get().
     /// That byte is taken from the buffer that was just scanned. Through get(),
     /// Apple Clang merged this read with the other get() calls of the scan
     /// function, which load the read position again right after it was stored
     /// (3% of json::accept() on jeopardy.json on Apple M1).
-    char_int_type get_after_string_run(std::true_type /*bulk*/)
+    template<bool Keep>
+    char_int_type get_after_string_run(std::true_type /*bulk*/, std::integral_constant<bool, Keep> keep)
     {
         // a pending unget must be consumed through the normal path first
         if (next_unget)
@@ -13300,7 +13305,7 @@ class lexer : public lexer_base<BasicJsonType>
         const std::size_t pos = lexer_string_bulk_run(data, remaining);
         if (pos != 0)
         {
-            token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(data), pos);
+            append_string_run(keep, data, pos);
             bulk_consume(reinterpret_cast<const char*>(data), pos);
         }
         if (pos == remaining)
@@ -13344,7 +13349,8 @@ class lexer : public lexer_base<BasicJsonType>
     }
 
     /// streaming input: no bulk fast path
-    char_int_type get_after_string_run(std::false_type /*bulk*/)
+    template<bool Keep>
+    char_int_type get_after_string_run(std::false_type /*bulk*/, std::integral_constant<bool, Keep> /*keep*/)
     {
         return get();
     }
@@ -13358,13 +13364,18 @@ class lexer : public lexer_base<BasicJsonType>
     may contain \0 bytes), and token_buffer.size() is the number of bytes in the
     string.
 
+    @param[in] keep  whether the string is copied into token_buffer; if false
+                     (accept(), see scan()), it is only checked, with the same
+                     errors, and token_buffer stays empty
+
     @return token_type::value_string if string could be successfully scanned,
             token_type::parse_error otherwise
 
     @note In case of errors, variable error_message contains a textual
           description.
     */
-    token_type scan_string()
+    template<bool Keep>
+    token_type scan_string(std::integral_constant<bool, Keep> keep)
     {
         // reset token_buffer (ignore opening quote)
         reset();
@@ -13376,7 +13387,7 @@ class lexer : public lexer_base<BasicJsonType>
         {
             // bulk-consume ordinary characters from contiguous input, then
             // get the next character, the one that ends the run
-            switch (get_after_string_run(std::integral_constant<bool, bulk_scan>()))
+            switch (get_after_string_run(std::integral_constant<bool, bulk_scan>(), keep))
             {
                 // end of file while parsing the string
                 case char_traits<char_type>::eof():
@@ -13398,35 +13409,35 @@ class lexer : public lexer_base<BasicJsonType>
                     {
                         // quotation mark
                         case '\"':
-                            add('\"');
+                            add_string_char(keep, '\"');
                             break;
                         // reverse solidus
                         case '\\':
-                            add('\\');
+                            add_string_char(keep, '\\');
                             break;
                         // solidus
                         case '/':
-                            add('/');
+                            add_string_char(keep, '/');
                             break;
                         // backspace
                         case 'b':
-                            add('\b');
+                            add_string_char(keep, '\b');
                             break;
                         // form feed
                         case 'f':
-                            add('\f');
+                            add_string_char(keep, '\f');
                             break;
                         // line feed
                         case 'n':
-                            add('\n');
+                            add_string_char(keep, '\n');
                             break;
                         // carriage return
                         case 'r':
-                            add('\r');
+                            add_string_char(keep, '\r');
                             break;
                         // tab
                         case 't':
-                            add('\t');
+                            add_string_char(keep, '\t');
                             break;
 
                         // unicode escapes
@@ -13494,10 +13505,7 @@ class lexer : public lexer_base<BasicJsonType>
                             JSON_ASSERT(0x00 <= codepoint && codepoint <= 0x10FFFF);
 
                             // translate codepoint into bytes
-                            encode_utf8(static_cast<std::uint32_t>(codepoint), [this](std::uint32_t byte)
+                            add_codepoint(keep, codepoint);
-                            {
-                                add(static_cast<char_int_type>(byte));
-                            });
 
                             break;
                         }
@@ -13680,7 +13688,7 @@ class lexer : public lexer_base<BasicJsonType>
                 case 0x7E:
                 case 0x7F:
                 {
-                    add(current);
+                    add_string_char(keep, current);
                     break;
                 }
 
@@ -13716,7 +13724,7 @@ class lexer : public lexer_base<BasicJsonType>
                 case 0xDE:
                 case 0xDF:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!next_byte_in_range({0x80, 0xBF})))
+                    if (JSON_HEDLEY_UNLIKELY(!next_byte_in_range(keep, {0x80, 0xBF})))
                     {
                         return token_type::parse_error;
                     }
@@ -13726,7 +13734,7 @@ class lexer : public lexer_base<BasicJsonType>
                 // U+0800..U+0FFF: bytes E0 A0..BF 80..BF
                 case 0xE0:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0xA0, 0xBF, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0xA0, 0xBF, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -13750,7 +13758,7 @@ class lexer : public lexer_base<BasicJsonType>
                 case 0xEE:
                 case 0xEF:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0x80, 0xBF, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0x80, 0xBF, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -13760,7 +13768,7 @@ class lexer : public lexer_base<BasicJsonType>
                 // U+D000..U+D7FF: bytes ED 80..9F 80..BF
                 case 0xED:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0x80, 0x9F, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0x80, 0x9F, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -13770,7 +13778,7 @@ class lexer : public lexer_base<BasicJsonType>
                 // U+10000..U+3FFFF F0 90..BF 80..BF 80..BF
                 case 0xF0:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0x90, 0xBF, 0x80, 0xBF, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0x90, 0xBF, 0x80, 0xBF, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -13782,7 +13790,7 @@ class lexer : public lexer_base<BasicJsonType>
                 case 0xF2:
                 case 0xF3:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0x80, 0xBF, 0x80, 0xBF, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0x80, 0xBF, 0x80, 0xBF, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -13792,7 +13800,7 @@ class lexer : public lexer_base<BasicJsonType>
                 // U+100000..U+10FFFF F4 80..8F 80..BF 80..BF
                 case 0xF4:
                 {
-                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range({0x80, 0x8F, 0x80, 0xBF, 0x80, 0xBF}))))
+                    if (JSON_HEDLEY_UNLIKELY(!(next_byte_in_range(keep, {0x80, 0x8F, 0x80, 0xBF, 0x80, 0xBF}))))
                     {
                         return token_type::parse_error;
                     }
@@ -14283,7 +14291,7 @@ scan_number_done:
     token_type convert_number(token_type number_type, std::size_t mantissa_end)
     {
         // accept() only needs to know whether the input is valid, so it sets
-        // discard_number_values (see json.hpp), and an integer token whose
+        // discard_values (see json.hpp), and an integer token whose
         // digit count shows that it fits is reported without calling
         // convert_integer(). A number with up to 18 digits always fits into
         // both std::uint64_t and std::int64_t (18 nines is about 1e18, below
@@ -14298,7 +14306,7 @@ scan_number_done:
         // json_sax_acceptor, whose number callbacks discard their argument and
         // return true, and the parser rejects neither integers nor finite
         // floats. value_unsigned/value_integer are left unset here, so a caller
-        // that reads the converted value must not set discard_number_values.
+        // that reads the converted value must not set discard_values.
         //
         // On contiguous input, scan_number_bulk_contiguous() converts integer
         // tokens itself and does not pass them to this function, unless
@@ -14306,7 +14314,7 @@ scan_number_done:
         // reached for input without bulk access (e.g. streams), with
         // JSON_DIAGNOSTIC_POSITIONS, or when scan_number_bulk_contiguous()
         // falls back to scan_number().
-        if (discard_number_values)
+        if (discard_values)
         {
             constexpr std::size_t safe_digit_count = 18;
             if (number_type == token_type::value_unsigned && token_buffer.size() <= safe_digit_count)
@@ -14557,7 +14565,7 @@ scan_number_done:
         // w < 10^19, so a value below 10^max_exponent10 cannot overflow, and a
         // value that underflows is a finite number as well. Only a token that
         // may overflow has to be converted to find out.
-        if (JSON_HEDLEY_UNLIKELY(discard_number_values && s.exponent + 19 <= std::numeric_limits<number_float_t>::max_exponent10))
+        if (JSON_HEDLEY_UNLIKELY(discard_values && s.exponent + 19 <= std::numeric_limits<number_float_t>::max_exponent10))
         {
             value_float = 0;
             return true;
@@ -14889,6 +14897,34 @@ scan_number_done:
         token_buffer.push_back(static_cast<typename string_t::value_type>(c));
     }
 
+    /// add a character of a string token; accept() checks the string but does
+    /// not keep its value (@a keep is false)
+    void add_string_char(std::true_type /*keep*/, char_int_type c)
+    {
+        token_buffer.push_back(static_cast<typename string_t::value_type>(c));
+    }
+
+    static void add_string_char(std::false_type /*keep*/, char_int_type /*c*/) noexcept {}
+
+    /// add the UTF-8 bytes of a code point from a \\u escape to a string token
+    void add_codepoint(std::true_type /*keep*/, int codepoint)
+    {
+        encode_utf8(static_cast<std::uint32_t>(codepoint), [this](std::uint32_t byte)
+        {
+            add(static_cast<char_int_type>(byte));
+        });
+    }
+
+    static void add_codepoint(std::false_type /*keep*/, int /*codepoint*/) noexcept {}
+
+    /// append a run of ordinary string characters (see get_after_string_run())
+    void append_string_run(std::true_type /*keep*/, const unsigned char* data, std::size_t n)
+    {
+        token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(data), n);
+    }
+
+    static void append_string_run(std::false_type /*keep*/, const unsigned char* /*data*/, std::size_t /*n*/) noexcept {}
+
   public:
     /////////////////////
     // value getters
@@ -15283,7 +15319,11 @@ scan_number_done:
 
             // string
             case '\"':
-                return scan_string();
+                // accept() (discard_values) checks strings without copying them
+                // into token_buffer. The choice is made once per string: a
+                // check inside the string loop made number-heavy documents up
+                // to 3 % slower (mesh.json, Apple M1)
+                return discard_values ? scan_string(std::false_type {}) : scan_string(std::true_type {});
 
             // number
             case '-':
@@ -15368,11 +15408,13 @@ scan_number_done:
     std::size_t decimal_point_position = std::string::npos;
 
     /// whether the caller only needs the token types and never looks at the
-    /// converted numeric values; set only by accept(), which parses through
+    /// values of number and string tokens; set only by accept(), which parses
-    /// json_sax_acceptor. When set, convert_number() skips converting integer
+    /// through json_sax_acceptor. When set, convert_number() skips converting
-    /// tokens whose digit count guarantees that they fit into 64 bits (see
+    /// integer tokens whose digit count guarantees that they fit into 64 bits
-    /// there)
+    /// (see there), floats are converted only when they may overflow (see
-    const bool discard_number_values = false;
+    /// convert_accumulated_float()), and strings are checked without being
+    /// copied into token_buffer (see scan())
+    const bool discard_values = false;
 };
 
 }  // namespace detail
@@ -18517,13 +18559,11 @@ class binary_reader
     bool get_cbor_negative_integer()
     {
         NumberType number{};
-        return get_number(number) && emit_cbor_negative_integer(number);
+        if (JSON_HEDLEY_UNLIKELY(!get_number(number)))
-    }
+        {
+            return false;
+        }
 
-    /// pass the CBOR negative integer -1 - @a number to the SAX parser
-    template<typename NumberType>
-    bool emit_cbor_negative_integer(const NumberType number)
-    {
         // the value is -1 - number, which fits into number_integer_t
         // whenever number does; the outer cast undoes the integral promotion
         // for number_integer_t types narrower than int
@@ -18748,7 +18788,7 @@ class binary_reader
             case 0x95:
             case 0x96:
             case 0x97:
-                return enter_cbor_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu));
+                return enter_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu));
 
             case 0x98: // array (one-byte uint8_t for n follows)
             case 0x99: // array (two-byte uint16_t for n follow)
@@ -18757,7 +18797,7 @@ class binary_reader
             {
                 std::uint64_t len{};
                 std::size_t size{};
-                return get_cbor_argument(len) && get_cbor_container_size(len, size, "array") && enter_cbor_array(size);
+                return get_cbor_argument(len) && get_cbor_container_size(len, size, "array") && enter_array(size);
             }
 
             case 0x9F: // array (indefinite length)
@@ -19454,181 +19494,6 @@ class binary_reader
         return true;
     }
 
-    /*!
-    @brief read a big-endian number of type @a NumberType at @a data
-    */
-    template<typename NumberType>
-    NumberType load_big_endian(const unsigned char* data) const noexcept
-    {
-        NumberType result{};
-        std::memcpy(&result, data, sizeof(NumberType));
-        if (is_little_endian)
-        {
-            byte_swap(result);
-        }
-        return result;
-    }
-
-    /*!
-    @brief read the integers, floats, booleans, and nulls that follow in a
-           definite-length array, without the per-element bookkeeping of
-           @ref parse_cbor_internal
-
-    Stops at the end of the array, at any other kind of value, and when fewer
-    than 9 bytes (the longest of these values) are left in the input, leaving
-    those to @ref parse_cbor_value, which reads them the same way.
-
-    The caller has checked that an element remains, that at least 9 bytes are
-    left, and that the next byte begins a scalar.
-
-    @param[in,out] remaining  the number of elements of the array not yet read
-    @return whether the SAX parser accepted the values
-    */
-    bool parse_cbor_scalar_run(std::size_t& remaining)
-    {
-        do
-        {
-            const auto* const data = reinterpret_cast<const unsigned char*>(ia.bulk_data());
-            const unsigned char head = data[0];
-            std::size_t size = 0;
-            bool accepted = true;
-            switch (head)
-            {
-                case 0x18:
-                    size = 2;
-                    accepted = emit_unsigned(data[1]);
-                    break;
-                case 0x19:
-                    size = 3;
-                    accepted = emit_unsigned(load_big_endian<std::uint16_t>(data + 1));
-                    break;
-                case 0x1A:
-                    size = 5;
-                    accepted = emit_unsigned(load_big_endian<std::uint32_t>(data + 1));
-                    break;
-                case 0x1B:
-                    size = 9;
-                    accepted = emit_unsigned(load_big_endian<std::uint64_t>(data + 1));
-                    break;
-                case 0x38:
-                    size = 2;
-                    accepted = emit_cbor_negative_integer(data[1]);
-                    break;
-                case 0x39:
-                    size = 3;
-                    accepted = emit_cbor_negative_integer(load_big_endian<std::uint16_t>(data + 1));
-                    break;
-                case 0x3A:
-                    size = 5;
-                    accepted = emit_cbor_negative_integer(load_big_endian<std::uint32_t>(data + 1));
-                    break;
-                case 0x3B:
-                    size = 9;
-                    accepted = emit_cbor_negative_integer(load_big_endian<std::uint64_t>(data + 1));
-                    break;
-                case 0xF4:
-                    size = 1;
-                    accepted = sax->boolean(false);
-                    break;
-                case 0xF5:
-                    size = 1;
-                    accepted = sax->boolean(true);
-                    break;
-                case 0xF6:
-                    size = 1;
-                    accepted = sax->null();
-                    break;
-                case 0xFA:
-                    size = 5;
-                    accepted = emit_float(load_big_endian<float>(data + 1));
-                    break;
-                case 0xFB:
-                    size = 9;
-                    accepted = emit_float(load_big_endian<double>(data + 1));
-                    break;
-                default:
-                    if (head <= 0x17)
-                    {
-                        size = 1;
-                        accepted = sax->number_unsigned(static_cast<number_unsigned_t>(head));
-                    }
-                    else if (head >= 0x20 && head <= 0x37)
-                    {
-                        size = 1;
-                        accepted = sax->number_integer(static_cast<std::int8_t>(0x20 - 1 - head));
-                    }
-                    else
-                    {
-                        // any other value is read by parse_cbor_value
-                        return true;
-                    }
-                    break;
-            }
-            // as if read by get() and get_number(): current is the head byte
-            ia.bulk_skip(size);
-            chars_read += size;
-            current = head;
-            --remaining;
-            if (JSON_HEDLEY_UNLIKELY(!accepted))
-            {
-                return false;
-            }
-        }
-        while (remaining != 0 && ia.bulk_remaining() >= 9);
-        return true;
-    }
-
-    /*!
-    @brief open a definite-length array and read the scalars it begins with
-           (see @ref parse_cbor_scalar_run)
-
-    Only the start of an array is tried, which covers arrays of numbers
-    (e.g. coordinates) but costs arrays of other values only one test, not one
-    per element.
-
-    @param[in] len  the number of elements
-    @return whether the SAX parser accepted the array and the values read
-    */
-    bool enter_cbor_array(const std::size_t len)
-    {
-        return enter_array(len) && (len == 0 || !cbor_scalar_follows(std::integral_constant<bool, bulk_scan> {})
-                                    || parse_cbor_array_start(std::integral_constant<bool, bulk_scan> {}));
-    }
-
-    /// whether a run of scalars can start at the next byte: at least 9 bytes
-    /// are left and the byte begins an integer, a float, a boolean, or null;
-    /// one test, so that an array of containers or strings makes no call
-    bool cbor_scalar_follows(std::true_type /*bulk*/) const
-    {
-        if (ia.bulk_remaining() < 9)
-        {
-            return false;
-        }
-        const auto head = static_cast<unsigned char>(*ia.bulk_data());
-        return head < 0x40 || head >= 0xF4;
-    }
-
-    /// input that is not contiguous: every value is read by parse_cbor_value
-    bool cbor_scalar_follows(std::false_type /*bulk*/) const noexcept
-    {
-        return false;
-    }
-
-    /// read the scalars the array just opened begins with; out of line, so
-    /// that @ref parse_cbor_value stays small enough to be inlined into
-    /// @ref parse_cbor_internal
-    JSON_HEDLEY_NEVER_INLINE
-    bool parse_cbor_array_start(std::true_type /*bulk*/)
-    {
-        return parse_cbor_scalar_run(container_stack.back().remaining);
-    }
-
-    /// input that is not contiguous: every value is read by parse_cbor_value
-    bool parse_cbor_array_start(std::false_type /*bulk*/) const noexcept
-    {
-        return true;
-    }
-
     /*!
     @brief read a CBOR value and everything nested inside it
 
@@ -19658,7 +19523,6 @@ class binary_reader
                 // pop_back() below, which destroys the container_stack element
                 // it would otherwise alias
                 const container_frame top = container_stack.back();
-                const bool is_object = top.is_object;
                 bool at_end = false;
 
                 if (top.remaining != npos)
@@ -19670,7 +19534,7 @@ class binary_reader
                     {
                         // claim the element about to be read
                         --container_stack.back().remaining;
-                        if (is_object)
+                        if (top.is_object)
                         {
                             get();
                         }
@@ -19683,7 +19547,7 @@ class binary_reader
                     // Testing for it consumes a byte, which is the first byte
                     // of the next element when it is not one.
                     at_end = (get() == 0xFF);
-                    fetch = is_object;
+                    fetch = top.is_object;
                 }
 
                 if (at_end)
@@ -19700,7 +19564,7 @@ class binary_reader
                     continue;
                 }
 
-                if (is_object)
+                if (top.is_object)
                 {
                     if (JSON_HEDLEY_UNLIKELY(!skip_cbor_key_tags(tag_handler)))
                     {
@@ -21645,13 +21509,13 @@ class binary_reader
                 return sax->null();
 
             case 0xFB:
-                return sax->number_float(static_cast<number_float_t>(-1.0), no_source);
+                return sax->number_float(static_cast<number_float_t>(-1.0), "");
 
             case 0xFC:
-                return sax->number_float(static_cast<number_float_t>(0.0), no_source);
+                return sax->number_float(static_cast<number_float_t>(0.0), "");
 
             case 0xFD:
-                return sax->number_float(static_cast<number_float_t>(1.0), no_source);
+                return sax->number_float(static_cast<number_float_t>(1.0), "");
 
             case 0xFF: // empty string
             {
@@ -22155,7 +22019,7 @@ class binary_reader
         {
             return out_of_range_error(exception_id::number_overflow, "number overflow", "value");
         }
-        return sax->number_float(result, no_source);
+        return sax->number_float(result, "");
     }
 
     /*!
@@ -22215,7 +22079,7 @@ class binary_reader
         }();
         return sax->number_float((half & 0x8000u) != 0
                                  ? static_cast<number_float_t>(-val)
-                                 : static_cast<number_float_t>(val), no_source);
+                                 : static_cast<number_float_t>(val), "");
     }
 
     /*!
@@ -22540,10 +22404,6 @@ class binary_reader
     /// the SAX parser
     json_sax_t* sax = nullptr;
 
-    /// the (empty) source text of every number_float event: binary formats
-    /// have none, and a string_t built for each float would cost more
-    const string_t no_source{};
-
     /// the containers that have been opened and not closed yet; see @ref container_frame
     std::vector<container_frame> container_stack{};
 
@@ -22763,9 +22623,9 @@ class parser
                     const bool allow_exceptions_ = true,
                     const bool ignore_comments = false,
                     const bool ignore_trailing_commas_ = false,
-                    const bool discard_number_values_ = false)
+                    const bool discard_values_ = false)
         : callback(std::move(cb))
-        , m_lexer(std::move(adapter), ignore_comments, discard_number_values_)
+        , m_lexer(std::move(adapter), ignore_comments, discard_values_)
         , allow_exceptions(allow_exceptions_)
         , ignore_trailing_commas(ignore_trailing_commas_)
     {
@@ -37162,11 +37022,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         const bool allow_exceptions = true,
         const bool ignore_comments = false,
         const bool ignore_trailing_commas = false,
-        const bool discard_number_values = false
+        const bool discard_values = false
                                  )
     {
         return ::nlohmann::detail::parser<basic_json, InputAdapterType>(std::move(adapter),
-            std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas, discard_number_values);
+            std::move(cb), allow_exceptions, ignore_comments, ignore_trailing_commas, discard_values);
     }
 
   private:

tests/src/unit-cbor.cpp

@@ -29,9 +29,7 @@ using nlohmann::json;
 #include "round_trip_corpus.hpp"
 #include "test_utils.hpp"
 #include "sax_countdown.hpp"
-#include "sax_event_loggers.hpp"
 using utils::SaxCountdown;
-using utils::SaxEventLogger;
 
 
 TEST_CASE("CBOR")
@@ -2448,78 +2446,6 @@ TEST_CASE("CBOR SAX parsing stops at every event")
     CHECK(count_events(std::vector<std::uint8_t>({0xBF, 0x61, 'a', 0x9F, 0x01, 0xFF, 0xFF})) == 6);
 }
 
-TEST_CASE("CBOR arrays of scalars from contiguous and non-contiguous input")
-{
-    // contiguous input reads the integers, floats, booleans, and nulls an
-    // array begins with in one loop, other input value by value; both must
-    // give the same events, value, or error for the complete document and for
-    // every truncation of it, and stop at every event a SAX handler rejects
-    const std::vector<std::uint8_t> cbor =
-    {
-        0xA3,                                                       // map(3)
-        0x61, 'a',                                                  // "a"
-        0x98, 0x16,                                                 // array(22)
-        0x00, 0x17, 0x18, 0xFF, 0x19, 0x01, 0x00,                   // 0, 23, 255, 256
-        0x1A, 0x00, 0x01, 0x00, 0x00,                               // 65536
-        0x1B, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,       // 18446744073709551615
-        0x20, 0x37, 0x38, 0xFF, 0x39, 0x01, 0x00,                   // -1, -24, -256, -257
-        0x3A, 0x00, 0x01, 0x00, 0x00,                               // -65537
-        0x3B, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,       // -18446744073709551616 (a float)
-        0x3B, 0x7F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,       // -9223372036854775808
-        0xF4, 0xF5, 0xF6,                                           // false, true, null
-        0xFA, 0x3F, 0xC0, 0x00, 0x00,                               // 1.5 (float32)
-        0xFB, 0xBF, 0xB9, 0x99, 0x99, 0x99, 0x99, 0x99, 0x9A,       // -0.1
-        0xF9, 0x3C, 0x00,                                           // 1.0 (float16, ends the loop)
-        0x01, 0x61, 'a',                                            // 1, "a"
-        0xFB, 0x40, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,       // 2.5
-        0x61, 'b',                                                  // "b"
-        0x83,                                                       // array(3)
-        0x82, 0xFB, 0x3F, 0xF4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // [1.25,
-        0xFB, 0xC0, 0x0E, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,       //  -3.75]
-        0x82, 0xFB, 0x3F, 0xF4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // [1.25,
-        0xFB, 0xC0, 0x0E, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,       //  -3.75]
-        0x80,                                                       // []
-        0x61, 'c',                                                  // "c"
-        0x84, 0xA0, 0x01, 0xC1, 0x02, 0x81, 0x03                    // [{}, 1, tag(1) 2, [3]]
-    };
-    const auto tags = json::cbor_tag_handler_t::ignore;
-
-    const json j = json::from_cbor(cbor, true, true, tags);
-    CHECK(j["a"].size() == 22);
-    CHECK(j["a"][5] == 18446744073709551615u);
-    CHECK(j["a"][11].is_number_float());
-    CHECK(j["a"][11] == -18446744073709551616.0);
-    CHECK(j["a"][12] == (std::numeric_limits<std::int64_t>::min)());
-    CHECK(j["a"][17] == -0.1);
-    CHECK(j["b"] == json::parse("[[1.25, -3.75], [1.25, -3.75], []]"));
-    CHECK(j["c"] == json::parse("[{}, 1, 2, [3]]"));
-
-    for (std::size_t length = 0; length <= cbor.size(); ++length)
-    {
-        CAPTURE(length)
-        const std::vector<std::uint8_t> contiguous(cbor.begin(), cbor.begin() + static_cast<std::ptrdiff_t>(length));
-        const std::list<std::uint8_t> bytewise(contiguous.begin(), contiguous.end());
-
-        CHECK(json::from_cbor(contiguous, true, false, tags).dump() == json::from_cbor(bytewise.begin(), bytewise.end(), true, false, tags).dump());
-
-        SaxEventLogger from_contiguous;
-        SaxEventLogger from_bytewise;
-        CHECK(json::sax_parse(contiguous, &from_contiguous, json::input_format_t::cbor, true, false, false, tags)
-              == json::sax_parse(bytewise.begin(), bytewise.end(), &from_bytewise, json::input_format_t::cbor, true, false, false, tags));
-        CHECK(from_contiguous.events == from_bytewise.events);
-    }
-
-    for (int events = 0; events <= 60; ++events)
-    {
-        CAPTURE(events)
-        const std::list<std::uint8_t> bytewise(cbor.begin(), cbor.end());
-        SaxCountdown from_contiguous(events);
-        SaxCountdown from_bytewise(events);
-        CHECK(json::sax_parse(cbor, &from_contiguous, json::input_format_t::cbor, true, false, false, tags)
-              == json::sax_parse(bytewise.begin(), bytewise.end(), &from_bytewise, json::input_format_t::cbor, true, false, false, tags));
-    }
-}
-
 TEST_CASE("CBOR indefinite-length strings do not recurse per chunk")
 {
     // Reading an indefinite-length string or byte array used to call itself

tests/src/unit-class_parser.cpp

@@ -2982,6 +2982,67 @@ TEST_CASE("accept() agrees with parse() on floats around the overflow limit")
     }
 }
 
+TEST_CASE("accept() agrees with parse() on strings, which it checks without copying them")
+{
+    // accept() scans strings and object keys with a separate instantiation of
+    // the string scanner that does not copy them into the token buffer; it
+    // must accept and reject exactly what parse() does
+    const std::vector<std::string> pieces =
+    {
+        "", "abc", R"(\"\\\/\b\f\n\r\t)", R"(\u0041\u00e4\u20AC)", "\\ud83d\\ude00", "\\uD83D\\uDE00",
+        "\\ud800", "\\udc00", "\\ud800\\u0041", "\\ud800x", "\\udbff\\udfff", "\\u12", "\\u12g4", "\\x", "\\",
+        "\xc3\xa4", "\xe2\x82\xac", "\xf0\x9f\x98\x80", "\xf4\x8f\xbf\xbf", "\xc0\xaf", "\xed\xa0\x80", "\xf4\x90\x80\x80",
+        "\xff", "\xe2\x82", "\xc3", "\x01", "\x1f", "\x7f", "\n", std::string(1, '\0')
+    };
+
+    for (std::size_t run = 0; run <= 70; ++run)
+    {
+        for (const std::string& piece : pieces)
+        {
+            // a run of ordinary characters puts the piece at every offset of the bulk scanners
+            const std::string str = std::string(run, 'a') + piece;
+            std::string opened = "\"";
+            opened += str;
+            std::string closed = opened;
+            closed += '"';
+            std::vector<std::string> texts;
+            texts.push_back(closed);
+            texts.push_back("[");
+            texts.back() += closed;
+            texts.back() += ']';
+            texts.push_back("{");
+            texts.back() += closed;
+            texts.back() += ":1}";
+            texts.push_back("{\"k\":");
+            texts.back() += closed;
+            texts.back() += ',';
+            texts.back() += closed;
+            texts.back() += ":[";
+            texts.back() += closed;
+            texts.back() += "]}";
+            texts.push_back("[");
+            texts.back() += opened;
+            for (const std::string& text : texts)
+            {
+                CAPTURE(text)
+                for (int options = 0; options < 4; ++options)
+                {
+                    const bool ignore_comments = (options & 1) != 0;
+                    const bool ignore_trailing_commas = (options & 2) != 0;
+                    const bool parses = !json::parse(text, nullptr, false, ignore_comments, ignore_trailing_commas).is_discarded();
+                    CHECK(json::accept(text, ignore_comments, ignore_trailing_commas) == parses);
+
+                    std::istringstream stream(text);
+                    CHECK(json::accept(stream, ignore_comments, ignore_trailing_commas) == parses);
+
+                    const std::list<char> chars(text.begin(), text.end());
+                    CHECK(json::accept(chars.begin(), chars.end(), ignore_comments, ignore_trailing_commas) == parses);
+                }
+            }
+        }
+    }
+}
+
 namespace
 {
 // a DOM parser that reports parse errors without throwing, as in the sax_no_exception example