UBJSON/BJData readers: read optimized arrays of numbers in one loop

An array with a type marker for a fixed-size number ($U, $i, $I, $l, $L,
$d, $D, and BJData's $u, $m, $M), including the data of a BJData ndarray,
gives its elements no markers. When the input is contiguous, read the
elements that are in the input in one loop - load, byte swap for the
format's byte order, emit - instead of one trip through
parse_ubjson_internal and get_ubjson_value per element. Elements the
input ends before, other types, and non-contiguous inputs are read as
before.

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

include/nlohmann/detail/input/binary_reader.hpp

@@ -22,6 +22,7 @@
     #include <bit>  //byteswap
 #endif
 
+#include <nlohmann/detail/bit_ops.hpp>
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/input/input_adapters.hpp>
 #include <nlohmann/detail/input/json_sax.hpp>
@@ -741,11 +742,13 @@ class binary_reader
     bool get_cbor_negative_integer()
     {
         NumberType number{};
-        if (JSON_HEDLEY_UNLIKELY(!get_number(number)))
-        {
-            return false;
-        }
+        return get_number(number) && emit_cbor_negative_integer(number);
+    }
 
+    /// 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
@@ -970,7 +973,7 @@ class binary_reader
             case 0x95:
             case 0x96:
             case 0x97:
-                return enter_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu));
+                return enter_cbor_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)
@@ -979,7 +982,7 @@ class binary_reader
             {
                 std::uint64_t len{};
                 std::size_t size{};
-                return get_cbor_argument(len) && get_cbor_container_size(len, size, "array") && enter_array(size);
+                return get_cbor_argument(len) && get_cbor_container_size(len, size, "array") && enter_cbor_array(size);
             }
 
             case 0x9F: // array (indefinite length)
@@ -1133,16 +1136,10 @@ class binary_reader
                 return get_half_float(false);
 
             case 0xFA: // Single-Precision Float (four-byte IEEE 754)
-            {
-                float number{};
-                return get_number(number) && emit_float(number);
-            }
+                return get_cbor_float<float>();
 
             case 0xFB: // Double-Precision Float (eight-byte IEEE 754)
-            {
-                double number{};
-                return get_number(number) && emit_float(number);
-            }
+                return get_cbor_float<double>();
 
             default: // anything else (0xFF is handled inside the other types)
             {
@@ -1151,6 +1148,16 @@ class binary_reader
         }
     }
 
+    /// read a single- or double-precision float (kept out of
+    /// parse_cbor_value, which is inlined into parse_cbor_internal)
+    template<typename NumberType>
+    JSON_HEDLEY_NEVER_INLINE
+    bool get_cbor_float()
+    {
+        NumberType number{};
+        return get_number(number) && emit_float(number);
+    }
+
     /*!
     @brief reports a nested indefinite-length CBOR string or byte array
     @param[in] type_name  name of the rejected string type
@@ -1676,6 +1683,157 @@ 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.
+
+    @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)
+    {
+        while (remaining != 0 && ia.bulk_remaining() >= 9)
+        {
+            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;
+            }
+        }
+        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 || parse_cbor_array_start(std::integral_constant<bool, bulk_scan> {}));
+    }
+
+    /// 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
 
@@ -1705,6 +1863,7 @@ 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)
@@ -1716,7 +1875,7 @@ class binary_reader
                     {
                         // claim the element about to be read
                         --container_stack.back().remaining;
-                        if (top.is_object)
+                        if (is_object)
                         {
                             get();
                         }
@@ -1729,7 +1888,7 @@ 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 = top.is_object;
+                    fetch = is_object;
                 }
 
                 if (at_end)
@@ -1746,7 +1905,7 @@ class binary_reader
                     continue;
                 }
 
-                if (top.is_object)
+                if (is_object)
                 {
                     if (JSON_HEDLEY_UNLIKELY(!skip_cbor_key_tags(tag_handler)))
                     {
@@ -1971,7 +2130,7 @@ class binary_reader
             case 0x9D:
             case 0x9E:
             case 0x9F:
-                return enter_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x0Fu));
+                return enter_msgpack_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x0Fu));
 
             // fixstr
             case 0xA0:
@@ -2102,13 +2261,13 @@ class binary_reader
             case 0xDC: // array 16
             {
                 std::uint16_t len{};
-                return get_number(len) && enter_array(static_cast<std::size_t>(len));
+                return get_number(len) && enter_msgpack_array(static_cast<std::size_t>(len));
             }
 
             case 0xDD: // array 32
             {
                 std::uint32_t len{};
-                return get_number(len) && enter_array(conditional_static_cast<std::size_t>(len));
+                return get_number(len) && enter_msgpack_array(conditional_static_cast<std::size_t>(len));
             }
 
             case 0xDE: // map 16
@@ -2450,6 +2609,138 @@ class binary_reader
         }
     }
 
+    /*!
+    @brief read the integers, floats, booleans, and nils that follow in a
+           MessagePack array, without the per-element bookkeeping of
+           @ref parse_msgpack_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_msgpack_value, which reads them the same way.
+
+    @param[in,out] remaining  the number of elements of the array not yet read
+    @return whether the SAX parser accepted the values
+    */
+    bool parse_msgpack_scalar_run(std::size_t& remaining)
+    {
+        while (remaining != 0 && ia.bulk_remaining() >= 9)
+        {
+            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 0xC0: // nil
+                    size = 1;
+                    accepted = sax->null();
+                    break;
+                case 0xC2: // false
+                    size = 1;
+                    accepted = sax->boolean(false);
+                    break;
+                case 0xC3: // true
+                    size = 1;
+                    accepted = sax->boolean(true);
+                    break;
+                case 0xCA: // float 32
+                    size = 5;
+                    accepted = emit_float(load_big_endian<float>(data + 1));
+                    break;
+                case 0xCB: // float 64
+                    size = 9;
+                    accepted = emit_float(load_big_endian<double>(data + 1));
+                    break;
+                case 0xCC: // uint 8
+                    size = 2;
+                    accepted = emit_unsigned(data[1]);
+                    break;
+                case 0xCD: // uint 16
+                    size = 3;
+                    accepted = emit_unsigned(load_big_endian<std::uint16_t>(data + 1));
+                    break;
+                case 0xCE: // uint 32
+                    size = 5;
+                    accepted = emit_unsigned(load_big_endian<std::uint32_t>(data + 1));
+                    break;
+                case 0xCF: // uint 64
+                    size = 9;
+                    accepted = emit_unsigned(load_big_endian<std::uint64_t>(data + 1));
+                    break;
+                case 0xD0: // int 8
+                    size = 2;
+                    accepted = emit_signed(static_cast<std::int8_t>(data[1]));
+                    break;
+                case 0xD1: // int 16
+                    size = 3;
+                    accepted = emit_signed(load_big_endian<std::int16_t>(data + 1));
+                    break;
+                case 0xD2: // int 32
+                    size = 5;
+                    accepted = emit_signed(load_big_endian<std::int32_t>(data + 1));
+                    break;
+                case 0xD3: // int 64
+                    size = 9;
+                    accepted = emit_signed(load_big_endian<std::int64_t>(data + 1));
+                    break;
+                default:
+                    if (head <= 0x7F)
+                    {
+                        // positive fixint
+                        size = 1;
+                        accepted = sax->number_unsigned(static_cast<number_unsigned_t>(head));
+                    }
+                    else if (head >= 0xE0)
+                    {
+                        // negative fixint
+                        size = 1;
+                        accepted = sax->number_integer(static_cast<std::int8_t>(head));
+                    }
+                    else
+                    {
+                        // any other value is read by parse_msgpack_value
+                        return true;
+                    }
+                    break;
+            }
+            // as if read by get() and get_number(): current is the last byte
+            ia.bulk_skip(size);
+            chars_read += size;
+            current = data[size - 1];
+            --remaining;
+            if (JSON_HEDLEY_UNLIKELY(!accepted))
+            {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /*!
+    @brief open a MessagePack array and read the scalars it begins with (see
+           @ref parse_msgpack_scalar_run)
+    @param[in] len  the number of elements
+    @return whether the SAX parser accepted the array and the values read
+    */
+    bool enter_msgpack_array(const std::size_t len)
+    {
+        return enter_array(len) && (len == 0 || parse_msgpack_array_start(std::integral_constant<bool, bulk_scan> {}));
+    }
+
+    /// read the scalars the array just opened begins with; out of line, so
+    /// that @ref parse_msgpack_value stays small enough to be inlined
+    JSON_HEDLEY_NEVER_INLINE
+    bool parse_msgpack_array_start(std::true_type /*bulk*/)
+    {
+        return parse_msgpack_scalar_run(container_stack.back().remaining);
+    }
+
+    /// input that is not contiguous: every value is read by parse_msgpack_value
+    bool parse_msgpack_array_start(std::false_type /*bulk*/) const noexcept
+    {
+        return true;
+    }
+
     /*!
     @brief read a MessagePack value and everything nested inside it
 
@@ -3255,6 +3546,107 @@ class binary_reader
         return unexpected_byte("invalid byte", "value");
     }
 
+    /*!
+    @brief read the elements of an optimized array of numbers (type marker
+           @a type) that are in the input, in one loop, without the
+           per-element bookkeeping of @ref parse_ubjson_internal
+
+    Values are emitted as @ref get_ubjson_value emits them. Types other than
+    the fixed-size integers and floats are left to @ref get_ubjson_value, as
+    are the elements the input ends before.
+
+    @param[in,out] remaining  the number of elements not yet read
+    @param[in] type  the type marker of the elements
+    @return whether the SAX parser accepted the values
+    */
+    JSON_HEDLEY_NEVER_INLINE
+    bool parse_ubjson_typed_run(std::size_t& remaining, const char_int_type type, std::true_type /*bulk*/)
+    {
+        const bool bjdata = input_format == input_format_t::bjdata;
+        switch (type)
+        {
+            case 'U':
+                return parse_ubjson_typed_run<std::uint8_t>(remaining);
+            case 'i':
+                return parse_ubjson_typed_run<std::int8_t>(remaining);
+            case 'I':
+                return parse_ubjson_typed_run<std::int16_t>(remaining);
+            case 'l':
+                return parse_ubjson_typed_run<std::int32_t>(remaining);
+            case 'L':
+                return parse_ubjson_typed_run<std::int64_t>(remaining);
+            case 'u':
+                return !bjdata || parse_ubjson_typed_run<std::uint16_t>(remaining);
+            case 'm':
+                return !bjdata || parse_ubjson_typed_run<std::uint32_t>(remaining);
+            case 'M':
+                return !bjdata || parse_ubjson_typed_run<std::uint64_t>(remaining);
+            case 'd':
+                return parse_ubjson_typed_run<float>(remaining);
+            case 'D':
+                return parse_ubjson_typed_run<double>(remaining);
+            default:
+                return true;
+        }
+    }
+
+    /// input that is not contiguous: every element is read by get_ubjson_value
+    bool parse_ubjson_typed_run(std::size_t& /*remaining*/, const char_int_type /*type*/, std::false_type /*bulk*/) const noexcept
+    {
+        return true;
+    }
+
+    template<typename NumberType>
+    bool parse_ubjson_typed_run(std::size_t& remaining)
+    {
+        constexpr std::size_t size = sizeof(NumberType);
+        const std::size_t count = (std::min)(remaining, ia.bulk_remaining() / size);
+        if (count == 0)
+        {
+            return true;
+        }
+        const auto* const data = reinterpret_cast<const unsigned char*>(ia.bulk_data());
+        // UBJSON stores numbers big-endian, BJData little-endian
+        const bool swap = is_little_endian != (input_format == input_format_t::bjdata);
+        std::size_t read = 0;
+        bool accepted = true;
+        while (read < count && accepted)
+        {
+            NumberType number{};
+            std::memcpy(&number, data + (read * size), size);
+            if (swap)
+            {
+                byte_swap(number);
+            }
+            ++read;
+            accepted = emit_ubjson_number(number);
+        }
+        // as if read by get_number(): current is the last byte read
+        ia.bulk_skip(read * size);
+        chars_read += read * size;
+        current = data[(read * size) - 1];
+        remaining -= read;
+        return accepted;
+    }
+
+    template<typename NumberType, enable_if_t<std::is_floating_point<NumberType>::value, int> = 0>
+    bool emit_ubjson_number(const NumberType number)
+    {
+        return emit_float(number);
+    }
+
+    template < typename NumberType, enable_if_t < std::is_integral<NumberType>::value&& std::is_signed<NumberType>::value, int > = 0 >
+    bool emit_ubjson_number(const NumberType number)
+    {
+        return emit_signed(number);
+    }
+
+    template < typename NumberType, enable_if_t < std::is_integral<NumberType>::value&& !std::is_signed<NumberType>::value, int > = 0 >
+    bool emit_ubjson_number(const NumberType number)
+    {
+        return emit_unsigned(number);
+    }
+
     /*!
     @return whether array creation completed
     */
@@ -3290,7 +3682,15 @@ class binary_reader
                 return false;
             }
 
-            for (std::size_t i = 0; i < size_and_type.first; ++i)
+            // the numbers that are in the input, in one loop; the rest (if
+            // the input ends early) one by one below
+            std::size_t remaining = size_and_type.first;
+            if (!nd_is_char && JSON_HEDLEY_UNLIKELY(!parse_ubjson_typed_run(remaining, size_and_type.second, std::integral_constant<bool, bulk_scan> {})))
+            {
+                return false;
+            }
+
+            for (std::size_t i = size_and_type.first - remaining; i < size_and_type.first; ++i)
             {
                 if (nd_is_char)
                 {
@@ -3350,7 +3750,8 @@ class binary_reader
                 container_stack.back().remaining = 0;
             }
 
-            return true;
+            return size_and_type.second == 0
+                   || parse_ubjson_typed_run(container_stack.back().remaining, size_and_type.second, std::integral_constant<bool, bulk_scan> {});
         }
 
         return enter_array(detail::unknown_size());
@@ -3691,13 +4092,13 @@ class binary_reader
                 return sax->null();
 
             case 0xFB:
-                return sax->number_float(static_cast<number_float_t>(-1.0), "");
+                return sax->number_float(static_cast<number_float_t>(-1.0), no_source);
 
             case 0xFC:
-                return sax->number_float(static_cast<number_float_t>(0.0), "");
+                return sax->number_float(static_cast<number_float_t>(0.0), no_source);
 
             case 0xFD:
-                return sax->number_float(static_cast<number_float_t>(1.0), "");
+                return sax->number_float(static_cast<number_float_t>(1.0), no_source);
 
             case 0xFF: // empty string
             {
@@ -4066,6 +4467,27 @@ class binary_reader
         return current;
     }
 
+    /// reverse the byte order of a double with a single byteswap(): GCC does
+    /// not merge the byte-wise swap of the generic version into one
+    static void byte_swap(double& number) noexcept
+    {
+        static_assert(sizeof(double) == sizeof(std::uint64_t), "double must have 64 bits");
+        std::uint64_t bits{};
+        std::memcpy(&bits, &number, sizeof(bits));
+        bits = byteswap(bits);
+        std::memcpy(&number, &bits, sizeof(bits));
+    }
+
+    /// reverse the byte order of a float with a single byteswap()
+    static void byte_swap(float& number) noexcept
+    {
+        static_assert(sizeof(float) == sizeof(std::uint32_t), "float must have 32 bits");
+        std::uint32_t bits{};
+        std::memcpy(&bits, &number, sizeof(bits));
+        bits = byteswap(bits);
+        std::memcpy(&number, &bits, sizeof(bits));
+    }
+
     template<class NumberType>
     static void byte_swap(NumberType& number)
     {
@@ -4201,7 +4623,7 @@ class binary_reader
         {
             return out_of_range_error(exception_id::number_overflow, "number overflow", "value");
         }
-        return sax->number_float(result, "");
+        return sax->number_float(result, no_source);
     }
 
     /*!
@@ -4261,7 +4683,7 @@ class binary_reader
         }();
         return sax->number_float((half & 0x8000u) != 0
                                  ? static_cast<number_float_t>(-val)
-                                 : static_cast<number_float_t>(val), "");
+                                 : static_cast<number_float_t>(val), no_source);
     }
 
     /*!
@@ -4586,6 +5008,10 @@ 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{};
 

tests/src/unit-bjdata.cpp

@@ -26,11 +26,14 @@ using nlohmann::ordered_json;
 #include <limits>
 #include <iostream>
 #include <fstream>
+#include <list>
 #include <set>
 #include "make_test_data_available.hpp"
 #include "test_utils.hpp"
 #include "sax_countdown.hpp"
+#include "sax_event_loggers.hpp"
 using utils::SaxCountdown;
+using utils::SaxEventLogger;
 
 
 // trait_test_arg and the "value_in_range_of trait" TEST_CASE_TEMPLATE_DEFINE
@@ -4746,3 +4749,75 @@ TEST_CASE("BJData optimized container type marker is validated for count 0")
         CHECK(json::from_bjdata(vb) == json::binary({}));
     }
 }
+
+TEST_CASE("BJData optimized arrays from contiguous and non-contiguous input")
+{
+    // contiguous input reads the numbers of an array with a type marker in
+    // one loop, other input number by number; 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
+    json document =
+    {
+        {"u8", {0, 200, 255}},
+        {"i8", {-5, 100, -128}},
+        {"i16", {-30000, 1000, 30000}},
+        {"i32", {-2000000000, 5, 70000}},
+        {"i64", {-9000000000000000000LL, 1, 5000000000LL}},
+        {"f64", {1.5, -0.1, 2.5}},
+        {"pairs", {{1.25, -3.75}, {1.25, -3.75}, json::array()}},
+        {"mixed", {1, "a", 2.5, nullptr}},
+        {"u16", {40000, 1, 65535}},
+        {"u32", {4000000000U, 1, 70000}},
+        {"u64", {18446744073709551615ULL, 1, 5000000000ULL}},
+        {"nd", {{"_ArrayType_", "double"}, {"_ArraySize_", {2, 2}}, {"_ArrayData_", {1.5, -2.5, 3.5, -4.5}}}},
+        {"nd8", {{"_ArrayType_", "uint8"}, {"_ArraySize_", {3}}, {"_ArrayData_", {1, 2, 3}}}},
+    };
+    const std::vector<std::uint8_t> encoded = json::to_bjdata(document, true, true);
+    CHECK(json::from_bjdata(encoded) == document);
+
+    for (std::size_t length = 0; length <= encoded.size(); ++length)
+    {
+        CAPTURE(length)
+        const std::vector<std::uint8_t> contiguous(encoded.begin(), encoded.begin() + static_cast<std::ptrdiff_t>(length));
+        const std::list<std::uint8_t> bytewise(contiguous.begin(), contiguous.end());
+
+        CHECK(json::from_bjdata(contiguous, true, false).dump() == json::from_bjdata(bytewise.begin(), bytewise.end(), true, false).dump());
+#if !defined(JSON_NOEXCEPTION)
+        std::string contiguous_error;
+        std::string bytewise_error;
+        try
+        {
+            static_cast<void>(json::from_bjdata(contiguous));
+        }
+        catch (const json::exception& e)
+        {
+            contiguous_error = e.what();
+        }
+        try
+        {
+            static_cast<void>(json::from_bjdata(bytewise.begin(), bytewise.end()));
+        }
+        catch (const json::exception& e)
+        {
+            bytewise_error = e.what();
+        }
+        CHECK(contiguous_error == bytewise_error);
+#endif
+
+        SaxEventLogger from_contiguous;
+        SaxEventLogger from_bytewise;
+        CHECK(json::sax_parse(contiguous, &from_contiguous, json::input_format_t::bjdata)
+              == json::sax_parse(bytewise.begin(), bytewise.end(), &from_bytewise, json::input_format_t::bjdata));
+        CHECK(from_contiguous.events == from_bytewise.events);
+    }
+
+    for (int events = 0; events <= 80; ++events)
+    {
+        CAPTURE(events)
+        const std::list<std::uint8_t> bytewise(encoded.begin(), encoded.end());
+        SaxCountdown from_contiguous(events);
+        SaxCountdown from_bytewise(events);
+        CHECK(json::sax_parse(encoded, &from_contiguous, json::input_format_t::bjdata)
+              == json::sax_parse(bytewise.begin(), bytewise.end(), &from_bytewise, json::input_format_t::bjdata));
+    }
+}

tests/src/unit-cbor.cpp

@@ -29,7 +29,9 @@ 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")
@@ -2446,6 +2448,78 @@ 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-msgpack.cpp

@@ -27,12 +27,15 @@ using nlohmann::json;
 #include <sstream>
 #include <iomanip>
 #include <limits>
+#include <list>
 #include <set>
 #include "make_test_data_available.hpp"
 #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("MessagePack")
@@ -2212,3 +2215,97 @@ TEST_CASE("MessagePack large strings and binaries (chunked reader)")
         }
     }
 }
+
+TEST_CASE("MessagePack arrays of scalars from contiguous and non-contiguous input")
+{
+    // contiguous input reads the integers, floats, booleans, and nils 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> msgpack =
+    {
+        0x83,                                                       // map(3)
+        0xA1, 'a',                                                  // "a"
+        0xDC, 0x00, 0x16,                                           // array 16 (22)
+        0x00, 0x7F, 0xCC, 0xFF, 0xCD, 0x01, 0x00,                   // 0, 127, 255, 256
+        0xCE, 0x00, 0x01, 0x00, 0x00,                               // 65536
+        0xCF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,       // 18446744073709551615
+        0xFF, 0xE0, 0xD0, 0x80, 0xD1, 0xFF, 0x00,                   // -1, -32, -128, -256
+        0xD2, 0xFF, 0xFE, 0xFF, 0xFF,                               // -65537
+        0xD3, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,       // -9223372036854775808
+        0xC2, 0xC3, 0xC0,                                           // false, true, nil
+        0xCA, 0x3F, 0xC0, 0x00, 0x00,                               // 1.5 (float 32)
+        0xCB, 0xBF, 0xB9, 0x99, 0x99, 0x99, 0x99, 0x99, 0x9A,       // -0.1
+        0xA1, 'x',                                                  // "x" (ends the loop)
+        0x01,                                                       // 1
+        0xCB, 0x40, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,       // 2.5
+        0xD9, 0x01, 'y',                                            // "y" (str 8)
+        0xC0,                                                       // nil
+        0xA1, 'b',                                                  // "b"
+        0x93,                                                       // fixarray(3)
+        0x92, 0xCB, 0x3F, 0xF4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // [1.25,
+        0xCB, 0xC0, 0x0E, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,       //  -3.75]
+        0x92, 0xCB, 0x3F, 0xF4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // [1.25,
+        0xCB, 0xC0, 0x0E, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,       //  -3.75]
+        0x90,                                                       // []
+        0xA1, 'c',                                                  // "c"
+        0x94, 0x80, 0x01, 0xC4, 0x01, 0x05, 0x91, 0x03              // [{}, 1, bin 8, [3]]
+    };
+
+    const json j = json::from_msgpack(msgpack);
+    CHECK(j["a"].size() == 22);
+    CHECK(j["a"][5] == 18446744073709551615u);
+    CHECK(j["a"][7] == -32);
+    CHECK(j["a"][11] == (std::numeric_limits<std::int64_t>::min)());
+    CHECK(j["a"][15] == 1.5);
+    CHECK(j["a"][16] == -0.1);
+    CHECK(j["a"][17] == "x");
+    CHECK(j["b"] == json::parse("[[1.25, -3.75], [1.25, -3.75], []]"));
+    CHECK(j["c"][2].is_binary());
+
+    for (std::size_t length = 0; length <= msgpack.size(); ++length)
+    {
+        CAPTURE(length)
+        const std::vector<std::uint8_t> contiguous(msgpack.begin(), msgpack.begin() + static_cast<std::ptrdiff_t>(length));
+        const std::list<std::uint8_t> bytewise(contiguous.begin(), contiguous.end());
+
+        CHECK(json::from_msgpack(contiguous, true, false).dump() == json::from_msgpack(bytewise.begin(), bytewise.end(), true, false).dump());
+#if !defined(JSON_NOEXCEPTION)
+        std::string contiguous_error;
+        std::string bytewise_error;
+        try
+        {
+            static_cast<void>(json::from_msgpack(contiguous));
+        }
+        catch (const json::parse_error& e)
+        {
+            contiguous_error = e.what();
+        }
+        try
+        {
+            static_cast<void>(json::from_msgpack(bytewise.begin(), bytewise.end()));
+        }
+        catch (const json::parse_error& e)
+        {
+            bytewise_error = e.what();
+        }
+        CHECK(contiguous_error == bytewise_error);
+#endif
+
+        SaxEventLogger from_contiguous;
+        SaxEventLogger from_bytewise;
+        CHECK(json::sax_parse(contiguous, &from_contiguous, json::input_format_t::msgpack)
+              == json::sax_parse(bytewise.begin(), bytewise.end(), &from_bytewise, json::input_format_t::msgpack));
+        CHECK(from_contiguous.events == from_bytewise.events);
+    }
+
+    for (int events = 0; events <= 60; ++events)
+    {
+        CAPTURE(events)
+        const std::list<std::uint8_t> bytewise(msgpack.begin(), msgpack.end());
+        SaxCountdown from_contiguous(events);
+        SaxCountdown from_bytewise(events);
+        CHECK(json::sax_parse(msgpack, &from_contiguous, json::input_format_t::msgpack)
+              == json::sax_parse(bytewise.begin(), bytewise.end(), &from_bytewise, json::input_format_t::msgpack));
+    }
+}

tests/src/unit-ubjson.cpp

@@ -21,12 +21,15 @@ using nlohmann::json;
 
 #include <iostream>
 #include <fstream>
+#include <list>
 #include <set>
 #include "make_test_data_available.hpp"
 #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("UBJSON")
@@ -3400,3 +3403,70 @@ TEST_CASE("UBJSON optimized container type marker is validated for count 0")
         }
     }
 }
+
+TEST_CASE("UBJSON optimized arrays from contiguous and non-contiguous input")
+{
+    // contiguous input reads the numbers of an array with a type marker in
+    // one loop, other input number by number; 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
+    json document =
+    {
+        {"u8", {0, 200, 255}},
+        {"i8", {-5, 100, -128}},
+        {"i16", {-30000, 1000, 30000}},
+        {"i32", {-2000000000, 5, 70000}},
+        {"i64", {-9000000000000000000LL, 1, 5000000000LL}},
+        {"f64", {1.5, -0.1, 2.5}},
+        {"pairs", {{1.25, -3.75}, {1.25, -3.75}, json::array()}},
+        {"mixed", {1, "a", 2.5, nullptr}},
+    };
+    const std::vector<std::uint8_t> encoded = json::to_ubjson(document, true, true);
+    CHECK(json::from_ubjson(encoded) == document);
+
+    for (std::size_t length = 0; length <= encoded.size(); ++length)
+    {
+        CAPTURE(length)
+        const std::vector<std::uint8_t> contiguous(encoded.begin(), encoded.begin() + static_cast<std::ptrdiff_t>(length));
+        const std::list<std::uint8_t> bytewise(contiguous.begin(), contiguous.end());
+
+        CHECK(json::from_ubjson(contiguous, true, false).dump() == json::from_ubjson(bytewise.begin(), bytewise.end(), true, false).dump());
+#if !defined(JSON_NOEXCEPTION)
+        std::string contiguous_error;
+        std::string bytewise_error;
+        try
+        {
+            static_cast<void>(json::from_ubjson(contiguous));
+        }
+        catch (const json::exception& e)
+        {
+            contiguous_error = e.what();
+        }
+        try
+        {
+            static_cast<void>(json::from_ubjson(bytewise.begin(), bytewise.end()));
+        }
+        catch (const json::exception& e)
+        {
+            bytewise_error = e.what();
+        }
+        CHECK(contiguous_error == bytewise_error);
+#endif
+
+        SaxEventLogger from_contiguous;
+        SaxEventLogger from_bytewise;
+        CHECK(json::sax_parse(contiguous, &from_contiguous, json::input_format_t::ubjson)
+              == json::sax_parse(bytewise.begin(), bytewise.end(), &from_bytewise, json::input_format_t::ubjson));
+        CHECK(from_contiguous.events == from_bytewise.events);
+    }
+
+    for (int events = 0; events <= 80; ++events)
+    {
+        CAPTURE(events)
+        const std::list<std::uint8_t> bytewise(encoded.begin(), encoded.end());
+        SaxCountdown from_contiguous(events);
+        SaxCountdown from_bytewise(events);
+        CHECK(json::sax_parse(encoded, &from_contiguous, json::input_format_t::ubjson)
+              == json::sax_parse(bytewise.begin(), bytewise.end(), &from_bytewise, json::input_format_t::ubjson));
+    }
+}