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This commit is contained in:
Suzy Wang 2022-11-08 20:51:35 -08:00
parent 9560306cdb
commit ba868801fa
1 changed files with 9 additions and 1 deletions
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10
base/base/bit_cast.h
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@ -13,12 +13,20 @@
template <typename To, typename From>
std::decay_t<To> bit_cast(const From & from)
{
/**
* Assume the source value is 0xAABBCCDD (i.e. sizeof(from) == 4).
* Its BE representation is 0xAABBCCDD, the LE representation is 0xDDCCBBAA.
* Further assume, sizeof(res) == 8 and that res is initially zeroed out.
* With LE, the result after bit_cast is 0xDDCCBBAA00000000 (no change to the previous behavior).
* With BE, we previously produced 0xAABBCCDD00000000 and we now produce 0x00000000AABBCCDD
*/
To res {};
static_assert(sizeof(From) <= sizeof(To));
if constexpr (std::endian::native == std::endian::little)
memcpy(static_cast<void*>(&res), &from, std::min(sizeof(res), sizeof(from)));
else
{
uint32_t offset = (sizeof(res) > sizeof(from)) ? (sizeof(res) - sizeof(from)) : 0;
uint32_t offset = sizeof(res) - sizeof(to);
memcpy(reinterpret_cast<char *>(&res) + offset, &from, std::min(sizeof(res), sizeof(from)));
}
return res;