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Merge pull request #3107 from lioncash/hashable

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common/hash: Remove unused HashableStruct
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Rodrigo Locatti 2019-11-13 17:30:30 -03:00 committed by GitHub
commit 7f424d0f60
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1 changed files with 0 additions and 35 deletions
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35
src/common/hash.h
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@ -35,41 +35,6 @@ static inline u64 ComputeStructHash64(const T& data) {
return ComputeHash64(&data, sizeof(data));
}
/// A helper template that ensures the padding in a struct is initialized by memsetting to 0.
template <typename T>
struct HashableStruct {
// In addition to being trivially copyable, T must also have a trivial default constructor,
// because any member initialization would be overridden by memset
static_assert(std::is_trivial_v<T>, "Type passed to HashableStruct must be trivial");
/*
* We use a union because "implicitly-defined copy/move constructor for a union X copies the
* object representation of X." and "implicitly-defined copy assignment operator for a union X
* copies the object representation (3.9) of X." = Bytewise copy instead of memberwise copy.
* This is important because the padding bytes are included in the hash and comparison between
* objects.
*/
union {
T state;
};
HashableStruct() {
// Memset structure to zero padding bits, so that they will be deterministic when hashing
std::memset(&state, 0, sizeof(T));
}
bool operator==(const HashableStruct<T>& o) const {
return std::memcmp(&state, &o.state, sizeof(T)) == 0;
};
bool operator!=(const HashableStruct<T>& o) const {
return !(*this == o);
};
std::size_t Hash() const {
return Common::ComputeStructHash64(state);
}
};
struct PairHash {
template <class T1, class T2>
std::size_t operator()(const std::pair<T1, T2>& pair) const noexcept {