json/tests/src/unit-bson.cpp

//     __ _____ _____ _____
//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
// |  |  |__   |  |  | | | |  version 3.12.0
// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
//
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
// SPDX-License-Identifier: MIT

#include "doctest_compatibility.h"

#include <nlohmann/json.hpp>
using nlohmann::json;

#include <cstdint>
#include <fstream>
#include <limits>
#include <sstream>
#include <vector>
#include "make_test_data_available.hpp"
#include "round_trip_corpus.hpp"
#include "test_utils.hpp"
#include "sax_countdown.hpp"
using utils::SaxCountdown;

namespace
{
// a binary container that reports a size beyond INT32_MAX without allocating
// that much memory, so the BSON length overflow can be tested cheaply
class huge_binary_t : public std::vector<std::uint8_t>
{
  public:
    using std::vector<std::uint8_t>::vector;

    size_type size() const noexcept // NOLINT(readability-convert-member-functions-to-static)
    {
        // one byte more than the BSON length field can represent
        return static_cast<size_type>((std::numeric_limits<std::int32_t>::max)()) + 1;
    }
};

using huge_binary_json = nlohmann::basic_json <
                         std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t,
                         double, std::allocator, nlohmann::adl_serializer, huge_binary_t, void >;

// a string type that can be made to report a size beyond INT32_MAX without
// allocating that much memory, so BSON length overflow can be tested for
// strings and (embedded) documents as well, following the same idea as
// huge_binary_t.
//
// Unlike huge_binary_t (which is only ever used as the BSON *value* type),
// this type doubles as basic_json's StringType and is therefore also used
// for *object keys* (e.g. "s" or "nested" below). Only the designated test
// value is meant to lie about its size - if every huge_string_t (including
// keys) reported a huge size, the running totals computed while walking the
// BSON document (see calc_bson_sizes in binary_writer.hpp)
// would need more than 32 bits, and on platforms where std::size_t is only
// 32 bits wide that arithmetic would silently wrap around, producing wrong
// (or even unguarded) lengths. The fake size is therefore opt-in via
// as_huge(), and plain strings - in particular object keys - keep reporting
// their real, small size.
class huge_string_t : public std::string
{
  public:
    using std::string::string;
    huge_string_t(const std::string& s) : std::string(s) {} // NOLINT(google-explicit-constructor,hicpp-explicit-conversions)

    // returns a copy of @a s whose size() pretends to be huge
    static huge_string_t as_huge(const std::string& s)
    {
        huge_string_t result(s);
        result.pretend_huge = true;
        return result;
    }

    size_type size() const noexcept
    {
        if (pretend_huge)
        {
            // one byte more than the BSON length field can represent
            return static_cast<size_type>((std::numeric_limits<std::int32_t>::max)()) + 1;
        }
        return std::string::size();
    }

  private:
    bool pretend_huge = false;
};

using huge_string_json = nlohmann::basic_json <
                         std::map, std::vector, huge_string_t, bool, std::int64_t, std::uint64_t,
                         double, std::allocator, nlohmann::adl_serializer, std::vector<std::uint8_t>, void >;
} // namespace

TEST_CASE("BSON")
{
    SECTION("individual values not supported")
    {
        SECTION("null")
        {
            json const j = nullptr;
            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is null", json::type_error&);
        }

        SECTION("boolean")
        {
            SECTION("true")
            {
                json const j = true;
                CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is boolean", json::type_error&);
            }

            SECTION("false")
            {
                json const j = false;
                CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is boolean", json::type_error&);
            }
        }

        SECTION("number")
        {
            json const j = 42;
            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is number", json::type_error&);
        }

        SECTION("float")
        {
            json const j = 4.2;
            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is number", json::type_error&);
        }

        SECTION("string")
        {
            json const j = "not supported";
            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is string", json::type_error&);
        }

        SECTION("array")
        {
            json const j = std::vector<int> {1, 2, 3, 4, 5, 6, 7};
            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is array", json::type_error&);
        }
    }

    SECTION("keys containing code-point U+0000 cannot be serialized to BSON")
    {
        json const j =
        {
            { std::string("en\0try", 6), true }
        };
#if JSON_DIAGNOSTICS
        CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.out_of_range.409] (/en) BSON key cannot contain code point U+0000 (at byte 2)", json::out_of_range&);
#else
        CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.out_of_range.409] BSON key cannot contain code point U+0000 (at byte 2)", json::out_of_range&);
#endif
    }

    SECTION("lengths exceeding INT32_MAX cannot be serialized to BSON")
    {
        // out_of_range.412 is thrown from a single shared helper
        // (to_bson_length) that guards the BSON length fields of binary
        // values, strings, and (embedded) documents alike
        SECTION("binary")
        {
            huge_binary_json j;
            j["b"] = huge_binary_json::binary(huge_binary_t{});

            CHECK_THROWS_WITH_AS(huge_binary_json::to_bson(j), "[json.exception.out_of_range.412] BSON length 2147483661 exceeds maximum of 2147483647", huge_binary_json::out_of_range&);
        }

        SECTION("string")
        {
            huge_string_json j;
            j["s"] = huge_string_t::as_huge("value");

            CHECK_THROWS_WITH_AS(huge_string_json::to_bson(j), "[json.exception.out_of_range.412] BSON length 2147483661 exceeds maximum of 2147483647", huge_string_json::out_of_range&);
        }

        SECTION("document")
        {
            // an oversized string nested one level deep makes the
            // *embedded* document's own length exceed INT32_MAX as well
            huge_string_json nested;
            nested["s"] = huge_string_t::as_huge("value");
            huge_string_json j;
            j["nested"] = nested;

            CHECK_THROWS_WITH_AS(huge_string_json::to_bson(j), "[json.exception.out_of_range.412] BSON length 2147483674 exceeds maximum of 2147483647", huge_string_json::out_of_range&);
        }
    }

    SECTION("string length must be at least 1")
    {
        // from https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=11175
        std::vector<std::uint8_t> const v =
        {
            0x20, 0x20, 0x20, 0x20,
            0x02,
            0x00,
            0x00, 0x00, 0x00, 0x80
        };
        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(v), "[json.exception.parse_error.112] parse error at byte 10: syntax error while parsing BSON string: string length must be at least 1, is -2147483648", json::parse_error&);
    }

    SECTION("objects")
    {
        SECTION("empty object")
        {
            json const j = json::object();
            std::vector<std::uint8_t> const expected =
            {
                0x05, 0x00, 0x00, 0x00, // size (little endian)
                // no entries
                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with bool")
        {
            json const j =
            {
                { "entry", true }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x0D, 0x00, 0x00, 0x00, // size (little endian)
                0x08,               // entry: boolean
                'e', 'n', 't', 'r', 'y', '\x00',
                0x01,           // value = true
                0x00                    // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with bool")
        {
            json const j =
            {
                { "entry", false }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x0D, 0x00, 0x00, 0x00, // size (little endian)
                0x08,               // entry: boolean
                'e', 'n', 't', 'r', 'y', '\x00',
                0x00,           // value = false
                0x00                    // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with bool from a non-0/1 byte (lenient parsing)")
        {
            // documented lenient behavior (see gh-5333): any non-zero byte
            // is accepted as `true`, not just 0x01
            std::vector<std::uint8_t> const input =
            {
                0x0D, 0x00, 0x00, 0x00, // size (little endian)
                0x08,               // entry: boolean
                'e', 'n', 't', 'r', 'y', '\x00',
                0x02,           // value = 0x02 (neither 0x00 nor 0x01)
                0x00                    // end marker
            };

            const json expected = { { "entry", true } };
            CHECK(json::from_bson(input) == expected);
        }

        SECTION("non-empty object with double")
        {
            json const j =
            {
                { "entry", 4.2 }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x14, 0x00, 0x00, 0x00, // size (little endian)
                0x01, /// entry: double
                'e', 'n', 't', 'r', 'y', '\x00',
                0xcd, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0x10, 0x40,
                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with string")
        {
            json const j =
            {
                { "entry", "bsonstr" }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x18, 0x00, 0x00, 0x00, // size (little endian)
                0x02, /// entry: string (UTF-8)
                'e', 'n', 't', 'r', 'y', '\x00',
                0x08, 0x00, 0x00, 0x00, 'b', 's', 'o', 'n', 's', 't', 'r', '\x00',
                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with null member")
        {
            json const j =
            {
                { "entry", nullptr }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x0C, 0x00, 0x00, 0x00, // size (little endian)
                0x0A, /// entry: null
                'e', 'n', 't', 'r', 'y', '\x00',
                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with integer (32-bit) member")
        {
            json const j =
            {
                { "entry", std::int32_t{0x12345678} }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x10, 0x00, 0x00, 0x00, // size (little endian)
                0x10, /// entry: int32
                'e', 'n', 't', 'r', 'y', '\x00',
                0x78, 0x56, 0x34, 0x12,
                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with integer (64-bit) member")
        {
            json const j =
            {
                { "entry", std::int64_t{0x1234567804030201} }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x14, 0x00, 0x00, 0x00, // size (little endian)
                0x12, /// entry: int64
                'e', 'n', 't', 'r', 'y', '\x00',
                0x01, 0x02, 0x03, 0x04, 0x78, 0x56, 0x34, 0x12,
                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with negative integer (32-bit) member")
        {
            json const j =
            {
                { "entry", std::int32_t{-1} }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x10, 0x00, 0x00, 0x00, // size (little endian)
                0x10, /// entry: int32
                'e', 'n', 't', 'r', 'y', '\x00',
                0xFF, 0xFF, 0xFF, 0xFF,
                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with negative integer (64-bit) member")
        {
            json const j =
            {
                { "entry", std::int64_t{-1} }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x10, 0x00, 0x00, 0x00, // size (little endian)
                0x10, /// entry: int32
                'e', 'n', 't', 'r', 'y', '\x00',
                0xFF, 0xFF, 0xFF, 0xFF,
                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with unsigned integer (64-bit) member")
        {
            json const j =
            {
                { "entry", std::uint64_t{0x1234567804030201} }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x14, 0x00, 0x00, 0x00, // size (little endian)
                0x12, /// entry: int64
                'e', 'n', 't', 'r', 'y', '\x00',
                0x01, 0x02, 0x03, 0x04, 0x78, 0x56, 0x34, 0x12,
                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with small unsigned integer member")
        {
            json const j =
            {
                { "entry", std::uint64_t{0x42} }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x10, 0x00, 0x00, 0x00, // size (little endian)
                0x10, /// entry: int32
                'e', 'n', 't', 'r', 'y', '\x00',
                0x42, 0x00, 0x00, 0x00,
                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with object member")
        {
            json const j =
            {
                { "entry", json::object() }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x11, 0x00, 0x00, 0x00, // size (little endian)
                0x03, /// entry: embedded document
                'e', 'n', 't', 'r', 'y', '\x00',

                0x05, 0x00, 0x00, 0x00, // size (little endian)
                // no entries
                0x00, // end marker (embedded document)

                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with array member")
        {
            json const j =
            {
                { "entry", json::array() }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x11, 0x00, 0x00, 0x00, // size (little endian)
                0x04, /// entry: embedded document
                'e', 'n', 't', 'r', 'y', '\x00',

                0x05, 0x00, 0x00, 0x00, // size (little endian)
                // no entries
                0x00, // end marker (embedded document)

                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with non-empty array member")
        {
            json const j =
            {
                { "entry", json::array({1, 2, 3, 4, 5, 6, 7, 8}) }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x49, 0x00, 0x00, 0x00, // size (little endian)
                0x04, /// entry: embedded document
                'e', 'n', 't', 'r', 'y', '\x00',

                0x3D, 0x00, 0x00, 0x00, // size (little endian)
                0x10, '0', 0x00, 0x01, 0x00, 0x00, 0x00,
                0x10, '1', 0x00, 0x02, 0x00, 0x00, 0x00,
                0x10, '2', 0x00, 0x03, 0x00, 0x00, 0x00,
                0x10, '3', 0x00, 0x04, 0x00, 0x00, 0x00,
                0x10, '4', 0x00, 0x05, 0x00, 0x00, 0x00,
                0x10, '5', 0x00, 0x06, 0x00, 0x00, 0x00,
                0x10, '6', 0x00, 0x07, 0x00, 0x00, 0x00,
                0x10, '7', 0x00, 0x08, 0x00, 0x00, 0x00,
                0x00, // end marker (embedded document)

                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("array elements with non-conforming keys (lenient parsing)")
        {
            // documented lenient behavior (see gh-5333): BSON array element
            // keys are not checked against the required decimal sequence
            // "0", "1", "2", ... - elements are taken in encoded order
            std::vector<std::uint8_t> const input =
            {
                0x26, 0x00, 0x00, 0x00, // size (little endian)
                0x04, 'e', 'n', 't', 'r', 'y', '\x00', // entry: embedded array

                0x1A, 0x00, 0x00, 0x00, // size (little endian)
                0x10, '5', 0x00, 0x0A, 0x00, 0x00, 0x00, // key "5" (bogus)      -> 10
                0x10, 'x', 0x00, 0x14, 0x00, 0x00, 0x00, // key "x" (non-numeric) -> 20
                0x10, '1', 0x00, 0x1E, 0x00, 0x00, 0x00, // key "1" (out of order) -> 30
                0x00, // end marker (embedded array)

                0x00 // end marker
            };

            const json expected = { { "entry", json::array({10, 20, 30}) } };
            CHECK(json::from_bson(input) == expected);
        }

        SECTION("non-empty object with binary member")
        {
            const size_t N = 10;
            const auto s = std::vector<std::uint8_t>(N, 'x');
            json const j =
            {
                { "entry", json::binary(s, 0) }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x1B, 0x00, 0x00, 0x00, // size (little endian)
                0x05, // entry: binary
                'e', 'n', 't', 'r', 'y', '\x00',

                0x0A, 0x00, 0x00, 0x00, // size of binary (little endian)
                0x00, // Generic binary subtype
                0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78,

                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("non-empty object with binary member without subtype")
        {
            const size_t N = 10;
            const auto s = std::vector<std::uint8_t>(N, 'x');
            json const j =
            {
                { "entry", json::binary(s) }
            };

            CHECK(!j.at("entry").get_binary().has_subtype());

            std::vector<std::uint8_t> const expected =
            {
                0x1B, 0x00, 0x00, 0x00, // size (little endian)
                0x05, // entry: binary
                'e', 'n', 't', 'r', 'y', '\x00',

                0x0A, 0x00, 0x00, 0x00, // size of binary (little endian)
                0x00, // Generic binary subtype
                0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78,

                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip adds the generic binary subtype
            const auto roundtrip = json::from_bson(result);
            CHECK(roundtrip != j);
            CHECK(roundtrip.at("entry").get_binary().has_subtype());
            CHECK(roundtrip.at("entry").get_binary().subtype() == 0);
            CHECK(json::from_bson(result, true, false) == roundtrip);
        }

        SECTION("non-empty object with binary member with subtype")
        {
            // an MD5 hash
            const std::vector<std::uint8_t> md5hash = {0xd7, 0x7e, 0x27, 0x54, 0xbe, 0x12, 0x37, 0xfe, 0xd6, 0x0c, 0x33, 0x98, 0x30, 0x3b, 0x8d, 0xc4};
            json const j =
            {
                { "entry", json::binary(md5hash, 5) }
            };

            std::vector<std::uint8_t> const expected =
            {
                0x21, 0x00, 0x00, 0x00, // size (little endian)
                0x05, // entry: binary
                'e', 'n', 't', 'r', 'y', '\x00',

                0x10, 0x00, 0x00, 0x00, // size of binary (little endian)
                0x05, // MD5 binary subtype
                0xd7, 0x7e, 0x27, 0x54, 0xbe, 0x12, 0x37, 0xfe, 0xd6, 0x0c, 0x33, 0x98, 0x30, 0x3b, 0x8d, 0xc4,

                0x00 // end marker
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }

        SECTION("binary member with subtype 0x02 (old binary) keeps its inner length prefix (lenient parsing)")
        {
            // documented lenient behavior (see gh-5333): the payload for
            // binary subtype 0x02 ("old binary") is returned as-is,
            // including its own inner 4-byte length prefix; it is not
            // stripped or reinterpreted
            std::vector<std::uint8_t> const input =
            {
                0x17, 0x00, 0x00, 0x00, // size (little endian)
                0x05, 'e', 'n', 't', 'r', 'y', '\x00', // entry: binary

                0x06, 0x00, 0x00, 0x00, // size of binary (little endian)
                0x02, // "old binary" subtype
                0x02, 0x00, 0x00, 0x00, // inner length prefix (part of the old-binary payload)
                0x68, 0x69, // payload ('h', 'i')

                0x00 // end marker
            };

            // the inner length prefix is part of the (unmodified) payload
            const std::vector<std::uint8_t> expected_payload = {0x02, 0x00, 0x00, 0x00, 0x68, 0x69};
            const json expected = { { "entry", json::binary(expected_payload, 0x02) } };
            CHECK(json::from_bson(input) == expected);
        }

        SECTION("Some more complex document")
        {
            json const j =
            {
                {"double", 42.5},
                {"entry", 4.2},
                {"number", 12345},
                {"object", {{ "string", "value" }}}
            };

            std::vector<std::uint8_t> const expected =
            {
                /*size */ 0x4f, 0x00, 0x00, 0x00,
                /*entry*/ 0x01, 'd',  'o',  'u',  'b',  'l',  'e',  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x45, 0x40,
                /*entry*/ 0x01, 'e',  'n',  't',  'r',  'y',  0x00, 0xcd, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0x10, 0x40,
                /*entry*/ 0x10, 'n',  'u',  'm',  'b',  'e',  'r',  0x00, 0x39, 0x30, 0x00, 0x00,
                /*entry*/ 0x03, 'o',  'b',  'j',  'e',  'c',  't',  0x00,
                /*entry: obj-size */ 0x17, 0x00, 0x00, 0x00,
                /*entry: obj-entry*/0x02, 's',  't',  'r',  'i',  'n',  'g', 0x00, 0x06, 0x00, 0x00, 0x00, 'v', 'a', 'l', 'u', 'e', 0,
                /*entry: obj-term.*/0x00,
                /*obj-term*/ 0x00
            };

            const auto result = json::to_bson(j);
            CHECK(result == expected);

            // roundtrip
            CHECK(json::from_bson(result) == j);
            CHECK(json::from_bson(result, true, false) == j);
        }
    }

    SECTION("Examples from https://bsonspec.org/faq.html")
    {
        SECTION("Example 1")
        {
            std::vector<std::uint8_t> input = {0x16, 0x00, 0x00, 0x00, 0x02, 'h', 'e', 'l', 'l', 'o', 0x00, 0x06, 0x00, 0x00, 0x00, 'w', 'o', 'r', 'l', 'd', 0x00, 0x00};
            const json parsed = json::from_bson(input);
            const json expected = {{"hello", "world"}};
            CHECK(parsed == expected);
            const auto dumped = json::to_bson(parsed);
            CHECK(dumped == input);
            CHECK(json::from_bson(dumped) == expected);
        }

        SECTION("Example 2")
        {
            std::vector<std::uint8_t> input = {0x31, 0x00, 0x00, 0x00, 0x04, 'B', 'S', 'O', 'N', 0x00, 0x26, 0x00, 0x00, 0x00, 0x02, 0x30, 0x00, 0x08, 0x00, 0x00, 0x00, 'a', 'w', 'e', 's', 'o', 'm', 'e', 0x00, 0x01, 0x31, 0x00, 0x33, 0x33, 0x33, 0x33, 0x33, 0x33, 0x14, 0x40, 0x10, 0x32, 0x00, 0xc2, 0x07, 0x00, 0x00, 0x00, 0x00};
            const json parsed = json::from_bson(input);
            const json expected = {{"BSON", {"awesome", 5.05, 1986}}};
            CHECK(parsed == expected);
            const auto dumped = json::to_bson(parsed);
            CHECK(dumped == input);
            CHECK(json::from_bson(dumped) == expected);
        }
    }
}

TEST_CASE("regression test - BSON binary subtype rejects a value that doesn't fit a single byte")
{
    json const doc255 = {{"b", json::binary({1, 2}, 255)}};
    CHECK(json::from_bson(json::to_bson(doc255))["b"].get_binary().subtype() == 255);

    CHECK_THROWS_AS(json::to_bson(json{{"b", json::binary({1, 2}, 256)}}), json::out_of_range);
#if JSON_DIAGNOSTICS
    CHECK_THROWS_WITH_AS(json::to_bson(json {{"b", json::binary({1, 2}, 300)}}), "[json.exception.out_of_range.415] (/b) subtype 300 is too large for the BSON binary subtype (max 255)", json::out_of_range);
#else
    CHECK_THROWS_WITH_AS(json::to_bson(json {{"b", json::binary({1, 2}, 300)}}), "[json.exception.out_of_range.415] subtype 300 is too large for the BSON binary subtype (max 255)", json::out_of_range);
#endif
}

TEST_CASE("BSON input/output_adapters")
{
    const json json_representation =
    {
        {"double", 42.5},
        {"entry", 4.2},
        {"number", 12345},
        {"object", {{ "string", "value" }}}
    };

    const std::vector<std::uint8_t> bson_representation =
    {
        /*size */ 0x4f, 0x00, 0x00, 0x00,
        /*entry*/ 0x01, 'd',  'o',  'u',  'b',  'l',  'e',  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x45, 0x40,
        /*entry*/ 0x01, 'e',  'n',  't',  'r',  'y',  0x00, 0xcd, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0x10, 0x40,
        /*entry*/ 0x10, 'n',  'u',  'm',  'b',  'e',  'r',  0x00, 0x39, 0x30, 0x00, 0x00,
        /*entry*/ 0x03, 'o',  'b',  'j',  'e',  'c',  't',  0x00,
        /*entry: obj-size */ 0x17, 0x00, 0x00, 0x00,
        /*entry: obj-entry*/0x02, 's',  't',  'r',  'i',  'n',  'g', 0x00, 0x06, 0x00, 0x00, 0x00, 'v', 'a', 'l', 'u', 'e', 0,
        /*entry: obj-term.*/0x00,
        /*obj-term*/ 0x00
    };

    json j2;
    CHECK_NOTHROW(j2 = json::from_bson(bson_representation));

    // compare parsed JSON values
    CHECK(json_representation == j2);

    SECTION("roundtrips")
    {
        SECTION("std::ostringstream")
        {
            std::basic_ostringstream<char> ss;
            json::to_bson(json_representation, ss);
            const json j3 = json::from_bson(ss.str());
            CHECK(json_representation == j3);
        }

        SECTION("std::string")
        {
            std::string s;
            json::to_bson(json_representation, s);
            const json j3 = json::from_bson(s);
            CHECK(json_representation == j3);
        }

        SECTION("std::vector")
        {
            std::vector<std::uint8_t> v;
            json::to_bson(json_representation, v);
            const json j3 = json::from_bson(v);
            CHECK(json_representation == j3);
        }
    }
}


TEST_CASE("Incomplete BSON Input")
{
    SECTION("Incomplete BSON Input 1")
    {
        std::vector<std::uint8_t> const incomplete_bson =
        {
            0x0D, 0x00, 0x00, 0x00, // size (little endian)
            0x08,                   // entry: boolean
            'e', 'n', 't'           // unexpected EOF
        };

        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(incomplete_bson), "[json.exception.parse_error.110] parse error at byte 9: syntax error while parsing BSON cstring: unexpected end of input", json::parse_error&);

        CHECK(json::from_bson(incomplete_bson, true, false).is_discarded());

        SaxCountdown scp(0);
        CHECK(!json::sax_parse(incomplete_bson, &scp, json::input_format_t::bson));
    }

    SECTION("Incomplete BSON Input 2")
    {
        std::vector<std::uint8_t> const incomplete_bson =
        {
            0x0D, 0x00, 0x00, 0x00, // size (little endian)
            0x08,                   // entry: boolean, unexpected EOF
        };

        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(incomplete_bson), "[json.exception.parse_error.110] parse error at byte 6: syntax error while parsing BSON cstring: unexpected end of input", json::parse_error&);
        CHECK(json::from_bson(incomplete_bson, true, false).is_discarded());

        SaxCountdown scp(0);
        CHECK(!json::sax_parse(incomplete_bson, &scp, json::input_format_t::bson));
    }

    SECTION("Incomplete BSON Input 3")
    {
        std::vector<std::uint8_t> const incomplete_bson =
        {
            0x41, 0x00, 0x00, 0x00, // size (little endian)
            0x04, /// entry: embedded document
            'e', 'n', 't', 'r', 'y', '\x00',

            0x35, 0x00, 0x00, 0x00, // size (little endian)
            0x10, 0x00, 0x01, 0x00, 0x00, 0x00,
            0x10, 0x00, 0x02, 0x00, 0x00, 0x00
            // missing input data...
        };

        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(incomplete_bson), "[json.exception.parse_error.110] parse error at byte 28: syntax error while parsing BSON element list: unexpected end of input", json::parse_error&);
        CHECK(json::from_bson(incomplete_bson, true, false).is_discarded());

        SaxCountdown scp(1);
        CHECK(!json::sax_parse(incomplete_bson, &scp, json::input_format_t::bson));
    }

    SECTION("Incomplete BSON Input 4")
    {
        std::vector<std::uint8_t> const incomplete_bson =
        {
            0x0D, 0x00, // size (incomplete), unexpected EOF
        };

        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(incomplete_bson), "[json.exception.parse_error.110] parse error at byte 3: syntax error while parsing BSON number: unexpected end of input", json::parse_error&);
        CHECK(json::from_bson(incomplete_bson, true, false).is_discarded());

        SaxCountdown scp(0);
        CHECK(!json::sax_parse(incomplete_bson, &scp, json::input_format_t::bson));
    }

    SECTION("Incomplete BSON Input 5")
    {
        std::vector<std::uint8_t> const incomplete_bson =
        {
            0x09, 0x00, 0x00, 0x00, // size (little endian)
            0x08,                   // entry: boolean
            'b', '\x00'             // key, unexpected EOF before the value
        };

        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(incomplete_bson), "[json.exception.parse_error.110] parse error at byte 8: syntax error while parsing BSON number: unexpected end of input", json::parse_error&);
        CHECK(json::from_bson(incomplete_bson, true, false).is_discarded());

        SaxCountdown scp(0);
        CHECK(!json::sax_parse(incomplete_bson, &scp, json::input_format_t::bson));
    }

    SECTION("Incomplete BSON Input 6")
    {
        std::vector<std::uint8_t> const incomplete_bson =
        {
            0x0F, 0x00, 0x00, 0x00, // size (little endian)
            0x05,                   // entry: binary
            'b', '\x00',            // key
            0x00, 0x00, 0x00, 0x00  // length, unexpected EOF before the subtype
        };

        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(incomplete_bson), "[json.exception.parse_error.110] parse error at byte 12: syntax error while parsing BSON number: unexpected end of input", json::parse_error&);
        CHECK(json::from_bson(incomplete_bson, true, false).is_discarded());

        SaxCountdown scp(0);
        CHECK(!json::sax_parse(incomplete_bson, &scp, json::input_format_t::bson));
    }

    SECTION("Improve coverage")
    {
        SECTION("key")
        {
            json const j = {{"key", "value"}};
            auto bson_vec = json::to_bson(j);
            SaxCountdown scp(2);
            CHECK(!json::sax_parse(bson_vec, &scp, json::input_format_t::bson));
        }

        SECTION("array")
        {
            json const j =
            {
                { "entry", json::array() }
            };
            auto bson_vec = json::to_bson(j);
            SaxCountdown scp(2);
            CHECK(!json::sax_parse(bson_vec, &scp, json::input_format_t::bson));
        }
    }
}

// the test catches the exceptions of invalid input
#if !defined(JSON_NOEXCEPTION)
TEST_CASE("BSON keys from contiguous and stream input")
{
    // contiguous input reads a key up to its \x00-byte in one step, a stream
    // reads it byte by byte; both must give the same value or error for the
    // complete document and for every truncation of it
    const json j = {{"", true}, {"k", {1, 2, 3}}, {std::string(40, 'x'), {{"nested key", "value"}}}};
    const std::vector<std::uint8_t> bson = json::to_bson(j);
    CHECK(json::from_bson(bson) == j);

    for (std::size_t length = 0; length <= bson.size(); ++length)
    {
        CAPTURE(length)
        const std::vector<std::uint8_t> input(bson.begin(), bson.begin() + static_cast<std::ptrdiff_t>(length));
        std::string from_vector;
        std::string from_stream;
        try
        {
            from_vector = json::from_bson(input).dump();
        }
        catch (const json::parse_error& e)
        {
            from_vector = e.what();
        }
        try
        {
            std::istringstream stream(std::string(input.begin(), input.end()));
            from_stream = json::from_bson(stream).dump();
        }
        catch (const json::parse_error& e)
        {
            from_stream = e.what();
        }
        CHECK(from_vector == from_stream);
    }
}
#endif

TEST_CASE("Negative size of binary value")
{
    // invalid BSON: the size of the binary value is -1
    std::vector<std::uint8_t> const input =
    {
        0x21, 0x00, 0x00, 0x00, // size (little endian)
        0x05, // entry: binary
        'e', 'n', 't', 'r', 'y', '\x00',

        0xFF, 0xFF, 0xFF, 0xFF, // size of binary (little endian)
        0x05, // MD5 binary subtype
        0xd7, 0x7e, 0x27, 0x54, 0xbe, 0x12, 0x37, 0xfe, 0xd6, 0x0c, 0x33, 0x98, 0x30, 0x3b, 0x8d, 0xc4,

        0x00 // end marker
    };
    json _;
    CHECK_THROWS_WITH_AS(_ = json::from_bson(input), "[json.exception.parse_error.112] parse error at byte 15: syntax error while parsing BSON binary: byte array length cannot be negative, is -1", json::parse_error);
}

TEST_CASE("Unsupported BSON input")
{
    std::vector<std::uint8_t> const bson =
    {
        0x0C, 0x00, 0x00, 0x00, // size (little endian)
        0xFF,                   // entry type: Min key (not supported yet)
        'e', 'n', 't', 'r', 'y', '\x00',
        0x00 // end marker
    };

    json _;
    CHECK_THROWS_WITH_AS(_ = json::from_bson(bson), "[json.exception.parse_error.114] parse error at byte 5: Unsupported BSON record type 0xFF", json::parse_error&);
    CHECK(json::from_bson(bson, true, false).is_discarded());

    SaxCountdown scp(0);
    CHECK(!json::sax_parse(bson, &scp, json::input_format_t::bson));
}

TEST_CASE("BSON document size mismatch")
{
    json _;

    SECTION("top-level document declaring more bytes than it contains")
    {
        // empty object, but the length prefix claims 6 bytes instead of 5
        std::vector<std::uint8_t> const input = {0x06, 0x00, 0x00, 0x00, 0x00};
        CHECK_THROWS_WITH_AS(_ = json::from_bson(input), "[json.exception.parse_error.112] parse error at byte 5: syntax error while parsing BSON document: document size 6 does not match the number of bytes read (5)", json::parse_error&);
        CHECK(json::from_bson(input, true, false).is_discarded());
    }

    SECTION("top-level document with a negative size")
    {
        std::vector<std::uint8_t> const input = {0xFF, 0xFF, 0xFF, 0xFF, 0x00};
        CHECK_THROWS_WITH_AS(_ = json::from_bson(input), "[json.exception.parse_error.112] parse error at byte 5: syntax error while parsing BSON document: document size -1 does not match the number of bytes read (5)", json::parse_error&);
        CHECK(json::from_bson(input, true, false).is_discarded());
    }

    SECTION("embedded document whose size disagrees with its terminator")
    {
        // the embedded document "d" declares 0x7FFFFFFF bytes but its 0x00
        // terminator falls right after {"a":null}; the length prefix would
        // otherwise let the following "h" element be read as a member of the
        // enclosing document instead of "d"
        std::vector<std::uint8_t> const input =
        {
            0x00, 0x00, 0x00, 0x00, // outer size
            0x03, 'd', 0x00,        // entry: embedded document "d"
            0xFF, 0xFF, 0xFF, 0x7F, //   embedded size 0x7FFFFFFF
            0x0A, 'a', 0x00,        //   entry: null "a"
            0x00,                   //   embedded end marker
            0x08, 'h', 0x00, 0x01,  // entry: bool "h" = true
            0x00                    // outer end marker
        };
        CHECK_THROWS_WITH_AS(_ = json::from_bson(input), "[json.exception.parse_error.112] parse error at byte 15: syntax error while parsing BSON document: document size 2147483647 does not match the number of bytes read (8)", json::parse_error&);
        CHECK(json::from_bson(input, true, false).is_discarded());
    }

    SECTION("embedded array whose size disagrees with its terminator")
    {
        // array [42] is 12 bytes, but the length prefix claims 13
        std::vector<std::uint8_t> const input =
        {
            0x00, 0x00, 0x00, 0x00, // outer size
            0x04, 'a', 0x00,        // entry: array "a"
            0x0D, 0x00, 0x00, 0x00, //   array size 13 (real is 12)
            0x10, '0', 0x00, 0x2A, 0x00, 0x00, 0x00, //   entry: int32 "0" = 42
            0x00,                   //   array end marker
            0x00                    // outer end marker
        };
        CHECK_THROWS_WITH_AS(_ = json::from_bson(input), "[json.exception.parse_error.112] parse error at byte 19: syntax error while parsing BSON document: document size 13 does not match the number of bytes read (12)", json::parse_error&);
        CHECK(json::from_bson(input, true, false).is_discarded());
    }
}

TEST_CASE("BSON nesting does not consume the call stack")
{
    // An embedded document or array used to be read by calling back into the
    // document reader, so the native call stack grew with the nesting depth of
    // the input (#5104). The open documents are kept on a heap stack now.
    //
    // Deeply nested values must not be compared, copied or dumped here: those
    // operations are still recursive and would reintroduce the crash.

    // A document nested deeply enough to have crashed. The bytes are built
    // here rather than with to_bson(), because the writer still recurses once
    // per level and would overflow the stack before the reader is ever
    // reached. Every level is
    //     <int32 size> 0x03 'a' 0x00 <inner document> 0x00
    // so a level is eight bytes larger than the one it holds, and the sizes
    // can be filled in from the outside in.
    const std::size_t depth = 30000;
    std::vector<uint8_t> input;
    input.reserve(5 + (8 * depth));
    for (std::size_t i = 0; i < depth; ++i)
    {
        const auto size = static_cast<std::uint32_t>(5 + (8 * (depth - i)));
        input.push_back(static_cast<uint8_t>(size & 0xFF));
        input.push_back(static_cast<uint8_t>((size >> 8) & 0xFF));
        input.push_back(static_cast<uint8_t>((size >> 16) & 0xFF));
        input.push_back(static_cast<uint8_t>((size >> 24) & 0xFF));
        input.push_back(0x03); // embedded document
        input.push_back('a');
        input.push_back(0x00);
    }
    // the innermost document is empty, then one terminator closes each level
    input.insert(input.end(), {0x05, 0x00, 0x00, 0x00, 0x00});
    input.insert(input.end(), depth, 0x00);

    SECTION("a well-formed deep document is read through the SAX interface")
    {
        SaxCountdown accept_all(1000000);
        CHECK(json::sax_parse(input, &accept_all, json::input_format_t::bson));
    }

    SECTION("a well-formed deep document is read into a value")
    {
        json j = json::from_bson(input);

        // walked rather than compared: comparing, copying or dumping a value
        // this deep is still recursive
        std::size_t measured = 0;
        const json* q = &j;
        while (q->is_object() && !q->empty())
        {
            q = &q->begin().value();
            ++measured;
        }
        CHECK(measured == depth);
    }

    SECTION("embedded documents and arrays are still read the same way")
    {
        const json values = {{"a", {{"b", {{"c", 1}}}}}};
        CHECK(json::from_bson(json::to_bson(values)) == values);

        const json array = {{"a", {1, 2, 3}}};
        CHECK(json::from_bson(json::to_bson(array)) == array);

        const json mixed = {{"a", {json{{"x", 1}}, json{{"y", 2}}}}};
        CHECK(json::from_bson(json::to_bson(mixed)) == mixed);

        CHECK(json::from_bson(json::to_bson(json::object())) == json::object());
    }

    SECTION("a size that does not match is still reported per document")
    {
        // the embedded document claims one byte too many
        std::vector<uint8_t> const bad =
        {
            0x15, 0x00, 0x00, 0x00, 0x03, 'a', 0x00,
            0x0D, 0x00, 0x00, 0x00, 0x08, 'b', 0x00, 0x01, 0x00,
            0x00
        };
        json _;
        CHECK_THROWS_AS(_ = json::from_bson(bad), json::parse_error&);
        CHECK(json::from_bson(bad, true, false).is_discarded());
    }
}

TEST_CASE("BSON input that cannot be read is discarded by every overload")
{
    std::vector<std::uint8_t> input = json::to_bson(json({{"a", {1, 2}}}));
    input.pop_back();

    json _;
    CHECK_THROWS_AS(_ = json::from_bson(input.begin(), input.end()), json::parse_error&);
    CHECK(json::from_bson(input, true, false).is_discarded());
    CHECK(json::from_bson(input.begin(), input.end(), true, false).is_discarded());
    CHECK(json::from_bson(input.data(), input.size(), true, false).is_discarded());
    CHECK(json::from_bson({input.data(), input.size()}, true, false).is_discarded());
}

TEST_CASE("BSON SAX parsing stops at every event")
{
    // Containers are opened and closed by the loop that reads them; a SAX
    // handler that rejects any event - including the end of a nested
    // container - must stop the parse right there.
    const auto count_events = [](const std::vector<std::uint8_t>& input)
    {
        int events = 0;
        while (true)
        {
            SaxCountdown scp(events);
            if (json::sax_parse(input, &scp, json::input_format_t::bson))
            {
                return events;
            }
            ++events;
            REQUIRE(events < 1000);
        }
    };

    // 20 events: every container kind closes inside another one
    const json j = json::parse(R"({"a": [1, {"b": []}], "c": {"d": [[2]]}})");
    CHECK(count_events(json::to_bson(j)) == 20);
}

TEST_CASE("BSON numerical data")
{
    SECTION("number")
    {
        SECTION("signed")
        {
            SECTION("std::int64_t: INT64_MIN .. INT32_MIN-1")
            {
                std::vector<int64_t> const numbers
                {
                    (std::numeric_limits<int64_t>::min)(),
                    -1000000000000000000LL,
                    -100000000000000000LL,
                    -10000000000000000LL,
                    -1000000000000000LL,
                    -100000000000000LL,
                    -10000000000000LL,
                    -1000000000000LL,
                    -100000000000LL,
                    -10000000000LL,
                    static_cast<std::int64_t>((std::numeric_limits<std::int32_t>::min)()) - 1,
                };

                for (const auto i : numbers)
                {

                    CAPTURE(i)

                    json const j =
                    {
                        { "entry", i }
                    };
                    CHECK(j.at("entry").is_number_integer());

                    std::uint64_t const iu = *reinterpret_cast<const std::uint64_t*>(&i);
                    std::vector<std::uint8_t> const expected_bson =
                    {
                        0x14u, 0x00u, 0x00u, 0x00u, // size (little endian)
                        0x12u, /// entry: int64
                        'e', 'n', 't', 'r', 'y', '\x00',
                        static_cast<std::uint8_t>((iu >> (8u * 0u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 1u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 2u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 3u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 4u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 5u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 6u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 7u)) & 0xffu),
                        0x00u // end marker
                    };

                    const auto bson = json::to_bson(j);
                    CHECK(bson == expected_bson);

                    auto j_roundtrip = json::from_bson(bson);

                    CHECK(j_roundtrip.at("entry").is_number_integer());
                    CHECK(j_roundtrip == j);
                    CHECK(json::from_bson(bson, true, false) == j);

                }
            }

            SECTION("signed std::int32_t: INT32_MIN .. INT32_MAX")
            {
                std::vector<int32_t> const numbers
                {
                    (std::numeric_limits<int32_t>::min)(),
                    -2147483647L,
                    -1000000000L,
                    -100000000L,
                    -10000000L,
                    -1000000L,
                    -100000L,
                    -10000L,
                    -1000L,
                    -100L,
                    -10L,
                    -1L,
                    0L,
                    1L,
                    10L,
                    100L,
                    1000L,
                    10000L,
                    100000L,
                    1000000L,
                    10000000L,
                    100000000L,
                    1000000000L,
                    2147483646L,
                    (std::numeric_limits<int32_t>::max)()
                };

                for (const auto i : numbers)
                {

                    CAPTURE(i)

                    json const j =
                    {
                        { "entry", i }
                    };
                    CHECK(j.at("entry").is_number_integer());

                    std::uint32_t const iu = *reinterpret_cast<const std::uint32_t*>(&i);
                    std::vector<std::uint8_t> const expected_bson =
                    {
                        0x10u, 0x00u, 0x00u, 0x00u, // size (little endian)
                        0x10u, /// entry: int32
                        'e', 'n', 't', 'r', 'y', '\x00',
                        static_cast<std::uint8_t>((iu >> (8u * 0u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 1u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 2u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 3u)) & 0xffu),
                        0x00u // end marker
                    };

                    const auto bson = json::to_bson(j);
                    CHECK(bson == expected_bson);

                    auto j_roundtrip = json::from_bson(bson);

                    CHECK(j_roundtrip.at("entry").is_number_integer());
                    CHECK(j_roundtrip == j);
                    CHECK(json::from_bson(bson, true, false) == j);

                }
            }

            SECTION("signed std::int64_t: INT32_MAX+1 .. INT64_MAX")
            {
                std::vector<int64_t> const numbers
                {
                    (std::numeric_limits<int64_t>::max)(),
                    1000000000000000000LL,
                    100000000000000000LL,
                    10000000000000000LL,
                    1000000000000000LL,
                    100000000000000LL,
                    10000000000000LL,
                    1000000000000LL,
                    100000000000LL,
                    10000000000LL,
                    static_cast<std::int64_t>((std::numeric_limits<int32_t>::max)()) + 1,
                };

                for (const auto i : numbers)
                {

                    CAPTURE(i)

                    json const j =
                    {
                        { "entry", i }
                    };
                    CHECK(j.at("entry").is_number_integer());

                    std::uint64_t const iu = *reinterpret_cast<const std::uint64_t*>(&i);
                    std::vector<std::uint8_t> const expected_bson =
                    {
                        0x14u, 0x00u, 0x00u, 0x00u, // size (little endian)
                        0x12u, /// entry: int64
                        'e', 'n', 't', 'r', 'y', '\x00',
                        static_cast<std::uint8_t>((iu >> (8u * 0u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 1u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 2u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 3u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 4u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 5u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 6u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 7u)) & 0xffu),
                        0x00u // end marker
                    };

                    const auto bson = json::to_bson(j);
                    CHECK(bson == expected_bson);

                    auto j_roundtrip = json::from_bson(bson);

                    CHECK(j_roundtrip.at("entry").is_number_integer());
                    CHECK(j_roundtrip == j);
                    CHECK(json::from_bson(bson, true, false) == j);

                }
            }
        }

        SECTION("unsigned")
        {
            SECTION("unsigned std::uint64_t: 0 .. INT32_MAX")
            {
                std::vector<std::uint64_t> const numbers
                {
                    0ULL,
                    1ULL,
                    10ULL,
                    100ULL,
                    1000ULL,
                    10000ULL,
                    100000ULL,
                    1000000ULL,
                    10000000ULL,
                    100000000ULL,
                    1000000000ULL,
                    2147483646ULL,
                    static_cast<std::uint64_t>((std::numeric_limits<int32_t>::max)())
                };

                for (const auto i : numbers)
                {

                    CAPTURE(i)

                    json const j =
                    {
                        { "entry", i }
                    };

                    auto iu = i;
                    std::vector<std::uint8_t> const expected_bson =
                    {
                        0x10u, 0x00u, 0x00u, 0x00u, // size (little endian)
                        0x10u, /// entry: int32
                        'e', 'n', 't', 'r', 'y', '\x00',
                        static_cast<std::uint8_t>((iu >> (8u * 0u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 1u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 2u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 3u)) & 0xffu),
                        0x00u // end marker
                    };

                    const auto bson = json::to_bson(j);
                    CHECK(bson == expected_bson);

                    auto j_roundtrip = json::from_bson(bson);

                    CHECK(j.at("entry").is_number_unsigned());
                    CHECK(j_roundtrip.at("entry").is_number_integer());
                    CHECK(j_roundtrip == j);
                    CHECK(json::from_bson(bson, true, false) == j);

                }
            }

            SECTION("unsigned std::uint64_t: INT32_MAX+1 .. INT64_MAX")
            {
                std::vector<std::uint64_t> const numbers
                {
                    static_cast<std::uint64_t>((std::numeric_limits<std::int32_t>::max)()) + 1,
                    4000000000ULL,
                    static_cast<std::uint64_t>((std::numeric_limits<std::uint32_t>::max)()),
                    10000000000ULL,
                    100000000000ULL,
                    1000000000000ULL,
                    10000000000000ULL,
                    100000000000000ULL,
                    1000000000000000ULL,
                    10000000000000000ULL,
                    100000000000000000ULL,
                    1000000000000000000ULL,
                    static_cast<std::uint64_t>((std::numeric_limits<std::int64_t>::max)()),
                };

                for (const auto i : numbers)
                {

                    CAPTURE(i)

                    json const j =
                    {
                        { "entry", i }
                    };

                    auto iu = i;
                    std::vector<std::uint8_t> const expected_bson =
                    {
                        0x14u, 0x00u, 0x00u, 0x00u, // size (little endian)
                        0x12u, /// entry: int64
                        'e', 'n', 't', 'r', 'y', '\x00',
                        static_cast<std::uint8_t>((iu >> (8u * 0u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 1u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 2u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 3u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 4u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 5u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 6u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 7u)) & 0xffu),
                        0x00u // end marker
                    };

                    const auto bson = json::to_bson(j);
                    CHECK(bson == expected_bson);

                    auto j_roundtrip = json::from_bson(bson);

                    CHECK(j.at("entry").is_number_unsigned());
                    CHECK(j_roundtrip.at("entry").is_number_integer());
                    CHECK(j_roundtrip == j);
                    CHECK(json::from_bson(bson, true, false) == j);
                }
            }

            SECTION("unsigned std::uint64_t: INT64_MAX+1 .. UINT64_MAX")
            {
                std::vector<std::uint64_t> const numbers
                {
                    static_cast<std::uint64_t>((std::numeric_limits<std::int64_t>::max)()) + 1ULL,
                    0xffffffffffffffff,
                };

                for (const auto i : numbers)
                {

                    CAPTURE(i)

                    json const j =
                    {
                        { "entry", i }
                    };

                    auto iu = i;
                    std::vector<std::uint8_t> const expected_bson =
                    {
                        0x14u, 0x00u, 0x00u, 0x00u, // size (little endian)
                        0x11u, /// entry: uint64
                        'e', 'n', 't', 'r', 'y', '\x00',
                        static_cast<std::uint8_t>((iu >> (8u * 0u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 1u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 2u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 3u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 4u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 5u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 6u)) & 0xffu),
                        static_cast<std::uint8_t>((iu >> (8u * 7u)) & 0xffu),
                        0x00u // end marker
                    };

                    const auto bson = json::to_bson(j);
                    CHECK(bson == expected_bson);

                    auto j_roundtrip = json::from_bson(bson);

                    CHECK(j.at("entry").is_number_unsigned());
                    CHECK(j_roundtrip.at("entry").is_number_unsigned());
                    CHECK(j_roundtrip == j);
                    CHECK(json::from_bson(bson, true, false) == j);
                }
            }

        }
    }
}

TEST_CASE("Parse BSON directly from a file using iterator and sentinel")
{
    std::string const filename = TEST_DATA_DIRECTORY "/json.org/1.json";

    std::ifstream f_json(filename);
    const json expected = json::parse(f_json);

    std::ifstream file(filename + ".bson", std::ios::binary);
    const std::istreambuf_iterator<char> first(file);
    const json parsed = json::from_bson(first, utils::istreambuf_sentinel{});
    CHECK(parsed == expected);
}

TEST_CASE("BSON round-trip invariants")
{
    // This checks what the parse_bson_fuzzer driver checks (see
    // tests/src/fuzzer-parse_bson.cpp), so that a regression shows up in CI
    // rather than as an OSS-Fuzz report: anything from_bson() returns (j1)
    // can be serialized, parsed back (j2), and serialized again to reproduce
    // the exact bytes. BSON only serializes objects, so non-object corpus
    // values are skipped.
    for (const auto& j0 : utils::round_trip_corpus::values())
    {
        if (!j0.is_object())
        {
            continue;
        }

        json j1;
        try
        {
            // turn the corpus value into a value as from_bson() returns it
            j1 = json::from_bson(json::to_bson(j0));
        }
        catch (const json::exception&)
        {
            // the fuzzer driver only ever sees values from_bson() actually
            // produced, so skip corpus values that do not survive the
            // round trip here, too
            continue;
        }

        INFO("j1 = " << j1.dump());
        const std::vector<std::uint8_t> vec = json::to_bson(j1);
        json j2;
        // anything the library writes must be parsable by the library
        REQUIRE_NOTHROW(j2 = json::from_bson(vec));
        CHECK(json::to_bson(j2) == vec);
    }
}

TEST_CASE("BSON roundtrips" * doctest::skip())
{
    SECTION("reference files")
    {
        for (const std::string filename :
                {
                    TEST_DATA_DIRECTORY "/json.org/1.json",
                    TEST_DATA_DIRECTORY "/json.org/2.json",
                    TEST_DATA_DIRECTORY "/json.org/3.json",
                    TEST_DATA_DIRECTORY "/json.org/4.json",
                    TEST_DATA_DIRECTORY "/json.org/5.json"
                })
        {
            CAPTURE(filename)

            {
                INFO_WITH_TEMP(filename + ": std::vector<std::uint8_t>");
                // parse JSON file
                std::ifstream f_json(filename);
                const json j1 = json::parse(f_json);

                // parse BSON file
                auto packed = utils::read_binary_file(filename + ".bson");
                json j2;
                CHECK_NOTHROW(j2 = json::from_bson(packed));

                // compare parsed JSON values
                CHECK(j1 == j2);
            }

            {
                INFO_WITH_TEMP(filename + ": std::ifstream");
                // parse JSON file
                std::ifstream f_json(filename);
                const json j1 = json::parse(f_json);

                // parse BSON file
                std::ifstream f_bson(filename + ".bson", std::ios::binary);
                json j2;
                CHECK_NOTHROW(j2 = json::from_bson(f_bson));

                // compare parsed JSON values
                CHECK(j1 == j2);
            }

            {
                INFO_WITH_TEMP(filename + ": uint8_t* and size");
                // parse JSON file
                std::ifstream f_json(filename);
                const json j1 = json::parse(f_json);

                // parse BSON file
                auto packed = utils::read_binary_file(filename + ".bson");
                json j2;
                CHECK_NOTHROW(j2 = json::from_bson({packed.data(), packed.size()}));

                // compare parsed JSON values
                CHECK(j1 == j2);
            }

            {
                INFO_WITH_TEMP(filename + ": output to output adapters");
                // parse JSON file
                std::ifstream f_json(filename);
                json const j1 = json::parse(f_json);

                // parse BSON file
                auto packed = utils::read_binary_file(filename + ".bson");

                {
                    INFO_WITH_TEMP(filename + ": output adapters: std::vector<std::uint8_t>");
                    std::vector<std::uint8_t> vec;
                    json::to_bson(j1, vec);

                    if (vec != packed)
                    {
                        // the exact serializations may differ due to the order of
                        // object keys; in these cases, just compare whether both
                        // serializations create the same JSON value
                        CHECK(json::from_bson(vec) == json::from_bson(packed));
                    }
                }
            }
        }
    }
}

TEST_CASE("BSON: deeply nested values")
{
    SECTION("documents and arrays round-trip at every depth")
    {
        // nested documents and arrays, with siblings on every level, so
        // every length prefix covers entries of both kinds
        json value = "leaf";
        for (std::size_t depth = 0; depth <= 300; ++depth)
        {
            CAPTURE(depth)
            const json document = {{"value", value}, {"n", depth}};
            CHECK(json::from_bson(json::to_bson(document)) == document);

value = depth % 2 == 0 ? json{{"a", std::move(value)}, {"b", {1, "x"}}} :
            json::array({std::move(value), depth, json::object()});
        }
    }

    SECTION("a key containing U+0000 is rejected before anything is written")
    {
        json value = json::object({{std::string("bad\0key", 7), 1}});
        for (std::size_t depth = 0; depth < 200; ++depth)
        {
            value = json{{"a", {{"b", 1}}}, {"z", std::move(value)}};
        }
        std::vector<std::uint8_t> output;
        CHECK_THROWS_AS(json::to_bson(value, output), json::out_of_range&);
        CHECK(output.empty());
    }

    SECTION("a binary subtype that doesn't fit a byte is rejected before anything is written (#5675)")
    {
        // the offending value is nested, so this also covers that the check
        // is not limited to a directly written value's own document
        json const j = {{"a", {{"b", json::binary({1, 2}, 300)}}}};

        std::vector<std::uint8_t> vector_output;
        CHECK_THROWS_AS(json::to_bson(j, vector_output), json::out_of_range&);
        CHECK(vector_output.empty());

        std::string string_output;
        CHECK_THROWS_AS(json::to_bson(j, string_output), json::out_of_range&);
        CHECK(string_output.empty());
    }

    SECTION("values nested too deeply for the call stack (#5392)")
    {
        // serializing recursed once per nesting level, and computed every
        // nested document's length by walking everything below it again.
        // The values are only parsed, serialized and walked, never copied or
        // compared, since those recurse too.
        const std::size_t depth = 100000;
        for (const bool objects :
                {
                    false, true
                })
        {
            CAPTURE(objects)
            std::string text = "{\"a\":";
            for (std::size_t i = 0; i < depth; ++i)
            {
                text += objects ? "{\"a\":" : "[";
            }
            text += "1";
            text.append(depth, objects ? '}' : ']');
            text += "}";

            const auto bson = json::to_bson(json::parse(text));
            const auto result = json::from_bson(bson);
            const json* p = &result.at("a");
            for (std::size_t i = 0; i < depth; ++i)
            {
                p = objects ? &p->at("a") : &p->at(0);
            }
            CHECK(*p == 1);
        }
    }
}

TEST_CASE("Invalid document size handling")
{
    SECTION("document size must be at least 5")
    {
        std::vector<std::uint8_t> const v = {0x04, 0x00, 0x00, 0x00, 0x00};
        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(v), "[json.exception.parse_error.112] parse error at byte 5: syntax error while parsing BSON document: document size 4 does not match the number of bytes read (5)", json::parse_error&);
        CHECK(json::from_bson(v, true, false).is_discarded());
    }

    SECTION("declared document size must match consumed bytes (extra trailing element)")
    {
        // Declares 5-byte empty document but appends an int32 element after the declared end.
        std::vector<std::uint8_t> const v =
        {
            0x05, 0x00, 0x00, 0x00,
            0x10, 'a', 'd', 'm', 'i', 'n', 0x00,
            0x01, 0x00, 0x00, 0x00,
            0x00
        };
        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(v), "[json.exception.parse_error.112] parse error at byte 16: syntax error while parsing BSON document: document size 5 does not match the number of bytes read (16)", json::parse_error&);
        CHECK(json::from_bson(v, true, false).is_discarded());
    }

    SECTION("declared document size must match consumed bytes (premature terminator)")
    {
        // Declares 32-byte document but only contains the size field followed by an immediate terminator.
        std::vector<std::uint8_t> const v =
        {
            0x20, 0x00, 0x00, 0x00,
            0x00
        };
        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(v), "[json.exception.parse_error.112] parse error at byte 5: syntax error while parsing BSON document: document size 32 does not match the number of bytes read (5)", json::parse_error&);
        CHECK(json::from_bson(v, true, false).is_discarded());
    }

    SECTION("array declared size must match consumed bytes")
    {
        // Outer object contains an array "a" that declares 5 bytes (empty) but
        // actually contains an int32 element before its terminator.
        std::vector<std::uint8_t> const v =
        {
            0x14, 0x00, 0x00, 0x00,                         // object size = 20
            0x04, 'a', 0x00,                                // key "a", array type
            0x05, 0x00, 0x00, 0x00,                         // array declared size = 5 (empty)
            0x10, '0', 0x00, 0x01, 0x00, 0x00, 0x00,        // extra int32 element "0" = 1
            0x00,                                           // array terminator
            0x00                                            // object terminator
        };
        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(v), "[json.exception.parse_error.112] parse error at byte 19: syntax error while parsing BSON document: document size 5 does not match the number of bytes read (12)", json::parse_error&);
        CHECK(json::from_bson(v, true, false).is_discarded());
    }

    SECTION("BSON string must end with 0x00")
    {
        // Length-prefixed string whose terminator byte is 'X' (0x58), not 0x00.
        std::vector<std::uint8_t> const v =
        {
            0x0F, 0x00, 0x00, 0x00,
            0x02, 's', 0x00,
            0x02, 0x00, 0x00, 0x00,
            'A', 'X',
            0x00
        };
        json _;
        CHECK_THROWS_WITH_AS(_ = json::from_bson(v), "[json.exception.parse_error.112] parse error at byte 13: syntax error while parsing BSON string: BSON string is not null-terminated", json::parse_error&);
        CHECK(json::from_bson(v, true, false).is_discarded());
    }
}