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#pragma once
#include <util/system/defaults.h>
#define FNV32INIT 2166136261U
#define FNV32PRIME 16777619U
#define FNV64INIT ULL(14695981039346656037)
#define FNV64PRIME ULL(1099511628211)
namespace NFnvPrivate {
template <class It>
constexpr ui32 FnvHash32(It b, It e, ui32 init) {
while (b != e) {
init = (init * FNV32PRIME) ^ (unsigned char)*b++;
}
return init;
}
template <class It>
constexpr ui64 FnvHash64(It b, It e, ui64 init) {
while (b != e) {
init = (init * FNV64PRIME) ^ (unsigned char)*b++;
}
return init;
}
template <unsigned N>
struct TFnvHelper;
#define DEF_FNV(t) \
template <> \
struct TFnvHelper<t> { \
static const ui##t Init = FNV##t##INIT; \
template <class It> \
static constexpr ui##t FnvHash(It b, It e, ui##t init) { \
return FnvHash##t(b, e, init); \
} \
};
DEF_FNV(32)
DEF_FNV(64)
#undef DEF_FNV
}
template <class T, class It>
static constexpr T FnvHash(It b, It e, T init) {
static_assert(sizeof(*b) == 1, "expect sizeof(*b) == 1");
return (T)NFnvPrivate::TFnvHelper<8 * sizeof(T)>::FnvHash(b, e, init);
}
template <class T, class It>
static constexpr T FnvHash(It b, It e) {
return FnvHash<T>(b, e, (T)NFnvPrivate::TFnvHelper<8 * sizeof(T)>::Init);
}
template <class T>
static constexpr T FnvHash(const void* buf, size_t len, T init) {
return FnvHash<T>((const unsigned char*)buf, (const unsigned char*)buf + len, init);
}
template <class T>
static constexpr T FnvHash(const void* buf, size_t len) {
return FnvHash<T>((const unsigned char*)buf, (const unsigned char*)buf + len);
}
template <class T, class Buf>
static constexpr T FnvHash(const Buf& buf) {
return FnvHash<T>(buf.data(), buf.size() * sizeof(*buf.data()));
}
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