fnv1a.hpp File Reference

#include <stddef.h>

Functions
size_t	fnv1a_hash_bytes (const unsigned char *first, size_t count)
	From https://github.com/microsoft/VCSamples/ in file VC2015Samples/_Hash_seq/fnv1a.hpp The internal hash function std::_Hash_seq(const unsigned char *), used to implement std::hash on some string types, was visible in recent versions of the Standard Library is not anymore visible (VC2017 15.3).
size_t	fnv1a_hash_string (const char *string)
size_t	fnv1a_hash_string (const wchar_t *string)

Function Documentation

fnv1a_hash_bytes()

size_t fnv1a_hash_bytes ( const unsigned char * first, size_t count )

inline

From https://github.com/microsoft/VCSamples/ in file VC2015Samples/_Hash_seq/fnv1a.hpp The internal hash function std::_Hash_seq(const unsigned char *), used to implement std::hash on some string types, was visible in recent versions of the Standard Library is not anymore visible (VC2017 15.3).

To remove this dependency, add the header (fnv1a.hpp) to any affected code, and then find and replace _Hash_seq by fnv1a_hash_bytes. You'll get identical behavior to the internal implementation in _Hash_seq.

                                                                         {
 #if defined(_WIN64)
    static_assert(sizeof(size_t) == 8, "This code is for 64-bit size_t.");
    const size_t fnv_offset_basis = 14695981039346656037ULL;
    const size_t fnv_prime = 1099511628211ULL;
 
 #else /* defined(_WIN64) */
    static_assert(sizeof(size_t) == 4, "This code is for 32-bit size_t.");
    const size_t fnv_offset_basis = 2166136261U;
    const size_t fnv_prime = 16777619U;
 #endif /* defined(_WIN64) */
 
    size_t result = fnv_offset_basis;
    for (size_t next = 0; next < count; ++next)
        {   // fold in another byte
        result ^= (size_t)first[next];
        result *= fnv_prime;
        }
    return (result);
}

fnv1a_hash_string() [1/2]

size_t fnv1a_hash_string ( const char * string )

inline

{
#if defined(_WIN64)
    static_assert(sizeof(size_t) == 8, "This code is for 64-bit size_t.");
    const size_t fnv_offset_basis = 14695981039346656037ULL;
    const size_t fnv_prime = 1099511628211ULL;
 
#else /* defined(_WIN64) */
    static_assert(sizeof(size_t) == 4, "This code is for 32-bit size_t.");
    const size_t fnv_offset_basis = 2166136261U;
    const size_t fnv_prime = 16777619U;
#endif /* defined(_WIN64) */
 
    size_t result = fnv_offset_basis;
    while (*string)
    { // fold in another byte
        result ^= (size_t)(*string);
        result *= fnv_prime;
        string++;
    }
    return (result);
}

fnv1a_hash_string() [2/2]

size_t fnv1a_hash_string ( const wchar_t * string )

inline

{
#if defined(_WIN64)
    static_assert(sizeof(size_t) == 8, "This code is for 64-bit size_t.");
    const size_t fnv_offset_basis = 14695981039346656037ULL;
    const size_t fnv_prime = 1099511628211ULL;
 
#else /* defined(_WIN64) */
    static_assert(sizeof(size_t) == 4, "This code is for 32-bit size_t.");
    const size_t fnv_offset_basis = 2166136261U;
    const size_t fnv_prime = 16777619U;
#endif /* defined(_WIN64) */
 
    size_t result = fnv_offset_basis;
    while (*string)
    { // fold in another byte
        result ^= (size_t)(*string);
        result *= fnv_prime;
        string++;
    }
    return (result);
}