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#pragma once
#pragma warning( disable : 4307 ) // '*': integral constant overflow
#pragma warning( disable : 4244 ) // possible loss of data
#include <cstdint>
#include <string>
using hash_t = unsigned int;
// used for compile-time FNV-1a 32bit hashes.
#define fnv( str ) \
[&]() { \
constexpr hash_t out = hash::fnv1a( str ); \
\
return out; \
}()
// used for compile-time FNV-1a 32bit hashes when above macro cant be used for constexpr variables.
#define fnv_const( str ) Hash::fnv1a_32( str )
namespace hash // FNV-1a ( Fowler-Noll-Vo hash ).
{
// FNV-1a constants.
enum : hash_t {
FNV1A_PRIME = 0x1000193,
FNV1A_BASIS = 0x811C9DC5
};
// compile-time strlen.
__forceinline constexpr size_t ct_strlen( const char *str ) {
size_t out = 1;
for( ; str[ out ] != '\0'; ++out );
return out;
}
// hash data.
__forceinline constexpr hash_t fnv1a( const uint8_t *data, const size_t len ) {
hash_t out = FNV1A_BASIS;
for( size_t i = 0; i < len; ++i )
out = ( out ^ data[ i ] ) * FNV1A_PRIME;
return out;
}
// hash c-style string.
__forceinline constexpr hash_t fnv1a( const char *str ) {
hash_t out = FNV1A_BASIS;
size_t len = ct_strlen( str );
for( size_t i = 0; i < len; ++i )
out = ( out ^ str[ i ] ) * FNV1A_PRIME;
return out;
}
// hash C++-style string ( runtime only ).
__forceinline hash_t fnv1a( const std::string &str ) {
return fnv1a( ( uint8_t* )str.c_str( ), str.length( ) );
}
}
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