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Common/Hash: static_assert on the type passed to HashableStruct

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wwylele 2018-03-14 15:37:47 +02:00
parent 30cc8c10cd
commit 9c785814e7
1 changed files with 8 additions and 6 deletions
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14
src/common/hash.h
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@ -22,21 +22,23 @@ static inline u64 ComputeHash64(const void* data, size_t len) {
}
/**
* Computes a 64-bit hash of a struct. In addition to being POD (trivially copyable and having
* standard layout), it is also critical that either the struct includes no padding, or that any
* padding is initialized to a known value by memsetting the struct to 0 before filling it in.
* Computes a 64-bit hash of a struct. In addition to being trivially copyable, it is also critical
* that either the struct includes no padding, or that any padding is initialized to a known value
* by memsetting the struct to 0 before filling it in.
*/
template <typename T>
static inline u64 ComputeStructHash64(const T& data) {
static_assert(
std::is_trivially_copyable<T>::value && std::is_standard_layout<T>::value,
"Type passed to ComputeStructHash64 must be trivially copyable and standard layout");
static_assert(std::is_trivially_copyable<T>(),
"Type passed to ComputeStructHash64 must be trivially copyable");
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<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