FNV1a.h

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// This file was released as public domain | original author: ruby0x1
// https://gist.github.com/ruby0x1/81308642d0325fd386237cfa3b44785c
 
#pragma once
#include <stddef.h>
#include <stdint.h>
 
//fnv1a 32 and 64 bit hash functions
// key is the data to hash, len is the size of the data (or how much of it to hash against)
// code license: public domain or equivalent
// post: https://notes.underscorediscovery.com/constexpr-fnv1a/
 
inline constexpr uint32_t hash_32_fnv1a(const char *const data, size_t len)
{
 
    uint32_t hash = 0x811c9dc5;
    uint32_t prime = 0x1000193;
 
    for (uint32_t i = 0; i < len; ++i) {
        uint8_t value = data[i];
        hash = hash ^ value;
        hash *= prime;
    }
 
    return hash;
 
} //hash_32_fnv1a
 
inline constexpr uint64_t hash_64_fnv1a(const char *const data, size_t len)
{
 
    uint64_t hash = 0xcbf29ce484222325;
    uint64_t prime = 0x100000001b3;
 
    for (uint64_t i = 0; i < len; ++i) {
        uint8_t value = data[i];
        hash = hash ^ value;
        hash *= prime;
    }
 
    return hash;
 
} //hash_64_fnv1a