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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 * Computes a 64-bit hash of a struct. In addition to being trivially copyable, it is also critical
* standard layout), it is also critical that either the struct includes no padding, or that any * that either the struct includes no padding, or that any padding is initialized to a known value
* padding is initialized to a known value by memsetting the struct to 0 before filling it in. * by memsetting the struct to 0 before filling it in.
*/ */
template <typename T> template <typename T>
static inline u64 ComputeStructHash64(const T& data) { static inline u64 ComputeStructHash64(const T& data) {
static_assert( static_assert(std::is_trivially_copyable<T>(),
std::is_trivially_copyable<T>::value && std::is_standard_layout<T>::value, "Type passed to ComputeStructHash64 must be trivially copyable");
"Type passed to ComputeStructHash64 must be trivially copyable and standard layout");
return ComputeHash64(&data, sizeof(data)); return ComputeHash64(&data, sizeof(data));
} }
/// A helper template that ensures the padding in a struct is initialized by memsetting to 0. /// A helper template that ensures the padding in a struct is initialized by memsetting to 0.
template <typename T> template <typename T>
struct HashableStruct { 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 * 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 * object representation of X." and "implicitly-defined copy assignment operator for a union X