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Specialize char_traits for std::byte to fix from_msgpack (fixes #4756) (#4760)

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* Specialize char_traits for std::byte to fix from_msgpack (fixes #4756)

Provide a char_traits<std::byte> specialization under __cpp_lib_byte
to allow parsing MessagePack data from containers of std::byte.

Signed-off-by: xuesongtap <tap91624@gmail.com>
Signed-off-by: yexiaochuan <tap91624@gmail.com>

* Fix comments for cstddef include and MessagePack tests

Signed-off-by: xuesongtap <tap91624@gmail.com>
Signed-off-by: yexiaochuan <tap91624@gmail.com>

* Fix include <cstddef> only when __cpp_lib_byte is defined and sufficient

Signed-off-by: yexiaochuan <tap91624@gmail.com>

* Fix clang-tidy warnings in MessagePack std::byte tests

Signed-off-by: yexiaochuan <tap91624@gmail.com>

* Fix handle return value in MessagePack tests

Signed-off-by: yexiaochuan <tap91624@gmail.com>

---------

Signed-off-by: xuesongtap <tap91624@gmail.com>
Signed-off-by: yexiaochuan <tap91624@gmail.com>
This commit is contained in:
Xiaochuan Ye
2025-04-28 22:19:47 +08:00
committed by GitHub
parent 6b9199382b
commit 3b02afb9d9
3 changed files with 131 additions and 2 deletions
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28
include/nlohmann/detail/meta/type_traits.hpp
View File

@@ -13,7 +13,9 @@
#include <tuple> // tuple
#include <type_traits> // false_type, is_constructible, is_integral, is_same, true_type
#include <utility> // declval
#if defined(__cpp_lib_byte) && __cpp_lib_byte >= 201603L
#include <cstddef> // byte
#endif
#include <nlohmann/detail/iterators/iterator_traits.hpp>
#include <nlohmann/detail/macro_scope.hpp>
#include <nlohmann/detail/meta/call_std/begin.hpp>
@@ -239,6 +241,30 @@ struct char_traits<signed char> : std::char_traits<char>
}
};
#if defined(__cpp_lib_byte) && __cpp_lib_byte >= 201603L
template<>
struct char_traits<std::byte> : std::char_traits<char>
{
using char_type = std::byte;
using int_type = uint64_t;
static int_type to_int_type(char_type c) noexcept
{
return static_cast<int_type>(std::to_integer<unsigned char>(c));
}
static char_type to_char_type(int_type i) noexcept
{
return std::byte(static_cast<unsigned char>(i));
}
static constexpr int_type eof() noexcept
{
return static_cast<int_type>(std::char_traits<char>::eof());
}
};
#endif
///////////////////
// is_ functions //
///////////////////

28
single_include/nlohmann/json.hpp
View File

@@ -3367,7 +3367,9 @@ NLOHMANN_JSON_NAMESPACE_END
#include <tuple> // tuple
#include <type_traits> // false_type, is_constructible, is_integral, is_same, true_type
#include <utility> // declval
#if defined(__cpp_lib_byte) && __cpp_lib_byte >= 201603L
#include <cstddef> // byte
#endif
// #include <nlohmann/detail/iterators/iterator_traits.hpp>
// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++
@@ -3776,6 +3778,30 @@ struct char_traits<signed char> : std::char_traits<char>
}
};
#if defined(__cpp_lib_byte) && __cpp_lib_byte >= 201603L
template<>
struct char_traits<std::byte> : std::char_traits<char>
{
using char_type = std::byte;
using int_type = uint64_t;
static int_type to_int_type(char_type c) noexcept
{
return static_cast<int_type>(std::to_integer<unsigned char>(c));
}
static char_type to_char_type(int_type i) noexcept
{
return std::byte(static_cast<unsigned char>(i));
}
static constexpr int_type eof() noexcept
{
return static_cast<int_type>(std::char_traits<char>::eof());
}
};
#endif
///////////////////
// is_ functions //
///////////////////

77
tests/src/unit-msgpack.cpp
View File

@@ -1880,3 +1880,80 @@ TEST_CASE("MessagePack roundtrips" * doctest::skip())
}
}
}
#ifdef JSON_HAS_CPP_17
// Test suite for verifying MessagePack handling with std::byte input
TEST_CASE("MessagePack with std::byte")
{
SECTION("std::byte compatibility")
{
SECTION("vector roundtrip")
{
json original =
{
{"name", "test"},
{"value", 42},
{"array", {1, 2, 3}}
};
std::vector<uint8_t> temp = json::to_msgpack(original);
// Convert the uint8_t vector to std::byte vector
std::vector<std::byte> msgpack_data(temp.size());
for (size_t i = 0; i < temp.size(); ++i)
{
msgpack_data[i] = std::byte(temp[i]);
}
// Deserialize from std::byte vector back to JSON
json from_bytes;
CHECK_NOTHROW(from_bytes = json::from_msgpack(msgpack_data));
CHECK(from_bytes == original);
}
SECTION("empty vector")
{
const std::vector<std::byte> empty_data;
CHECK_THROWS_WITH_AS([&]() {
[[maybe_unused]] auto result = json::from_msgpack(empty_data);
return true;
}(),
"[json.exception.parse_error.110] parse error at byte 1: syntax error while parsing MessagePack value: unexpected end of input",
json::parse_error&);
}
SECTION("comparison with workaround")
{
json original =
{
{"string", "hello"},
{"integer", 42},
{"float", 3.14},
{"boolean", true},
{"null", nullptr},
{"array", {1, 2, 3}},
{"object", {{"key", "value"}}}
};
std::vector<uint8_t> temp = json::to_msgpack(original);
std::vector<std::byte> msgpack_data(temp.size());
for (size_t i = 0; i < temp.size(); ++i)
{
msgpack_data[i] = std::byte(temp[i]);
}
// Attempt direct deserialization using std::byte input
json direct_result = json::from_msgpack(msgpack_data);
// Test the workaround approach: reinterpret as unsigned char* and use iterator range
const auto *const char_start = reinterpret_cast<unsigned char const*>(msgpack_data.data());
const auto *const char_end = char_start + msgpack_data.size();
json workaround_result = json::from_msgpack(char_start, char_end);
// Verify that the final deserialized JSON matches the original JSON
CHECK(direct_result == workaround_result);
CHECK(direct_result == original);
}
}
}
#endif