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Fix endianness bug in write_digit2_separated (#2699)

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* Fix endianness bug in write_digit2_separated

* Move endianness check to compile time if it possible

* Turn 8 into a constant
This commit is contained in:
Vladislav Shchapov
2022-01-05 03:23:42 +05:00
committed by GitHub
parent 17a5c808da
commit 214cf13f17
2 changed files with 18 additions and 2 deletions
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10
include/fmt/chrono.h
View File

@@ -558,7 +558,15 @@ inline void write_digit2_separated(char* buf, unsigned a, unsigned b,
auto usep = static_cast<unsigned long long>(sep); auto usep = static_cast<unsigned long long>(sep);
// Add ASCII '0' to each digit byte and insert separators. // Add ASCII '0' to each digit byte and insert separators.
digits |= 0x3030003030003030 | (usep << 16) | (usep << 40); digits |= 0x3030003030003030 | (usep << 16) | (usep << 40);
memcpy(buf, &digits, 8);
constexpr const size_t len = 8;
if (const_check(is_big_endian())) {
char tmp[len];
memcpy(tmp, &digits, len);
std::reverse_copy(tmp, tmp + len, buf);
} else {
memcpy(buf, &digits, len);
}
} }
template <typename Period> FMT_CONSTEXPR inline const char* get_units() { template <typename Period> FMT_CONSTEXPR inline const char* get_units() {

10
include/fmt/format.h
View File

@@ -296,10 +296,18 @@ FMT_CONSTEXPR20 auto bit_cast(const From& from) -> To {
} }
inline auto is_big_endian() -> bool { inline auto is_big_endian() -> bool {
#ifdef _WIN32
return false;
#elif defined(__BIG_ENDIAN__)
return true;
#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__)
return __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__;
#else
struct bytes { struct bytes {
char data[sizeof(int)]; char data[sizeof(int)];
}; };
return bit_cast<bytes>(1).data[0] == 0; return bit_cast<bytes>(1).data[0] == 0;
#endif
} }
// A fallback implementation of uintptr_t for systems that lack it. // A fallback implementation of uintptr_t for systems that lack it.
@@ -309,7 +317,7 @@ struct fallback_uintptr {
fallback_uintptr() = default; fallback_uintptr() = default;
explicit fallback_uintptr(const void* p) { explicit fallback_uintptr(const void* p) {
*this = bit_cast<fallback_uintptr>(p); *this = bit_cast<fallback_uintptr>(p);
if (is_big_endian()) { if (const_check(is_big_endian())) {
for (size_t i = 0, j = sizeof(void*) - 1; i < j; ++i, --j) for (size_t i = 0, j = sizeof(void*) - 1; i < j; ++i, --j)
std::swap(value[i], value[j]); std::swap(value[i], value[j]);
} }