#pragma once

#include <stdint.h>

// FNV1a c++11 constexpr compile time hash functions, 32 and 64 bit
// str should be a null terminated string literal, value should be left out 
// e.g hash_32_fnv1a_const("example")
// code license: public domain or equivalent
// post: https://notes.underscorediscovery.com/constexpr-fnv1a/

constexpr uint32_t val_32_const = 0x811c9dc5;
constexpr uint32_t prime_32_const = 0x1000193;

constexpr uint64_t val_64_const = 0xcbf29ce484222325;
constexpr uint64_t prime_64_const = 0x100000001b3;

inline constexpr uint32_t hash_32_fnv1a_const( const char* const str , const uint32_t value = val_32_const ) noexcept
{
    return ( str[0] == '\0' ) ? value : hash_32_fnv1a_const( &str[1] , ( value ^ uint32_t( (uint8_t)str[0] ) ) * prime_32_const );
}

inline constexpr uint64_t hash_64_fnv1a_const( const char* const str , const uint64_t value = val_64_const ) noexcept
{
    return ( str[0] == '\0' ) ? value : hash_64_fnv1a_const( &str[1] , ( value ^ uint64_t( (uint8_t)str[0] ) ) * prime_64_const );
}
