/* SPDX-License-Identifier: MIT */
/**
 * hash.h - implementations of the FNV1a hashing algorithm.
 *
 * Copyright (c) 2022-2023 - Yaroslav de la Peña Smirnov
 */
#ifndef HMAP_HASH_H
#define HMAP_HASH_H

#include <inttypes.h>
#include <stdlib.h>

#if SIZE_MAX == 0xFFFFFFFF
/* size_t is 32bit */
static const size_t fnv_prime	= 16777619u;
static const size_t fnv_offsetb = 2166136261u;
#elif SIZE_MAX == 0xFFFFFFFFFFFFFFFF
/* size_t is 64bit */
static const size_t fnv_prime	= 1099511628211u;
static const size_t fnv_offsetb = 14695981039346656037u;
#endif

/**
 * fnv1a_bytes_hash() - generic fnv1a hash function.
 * @data:	pointer to data to hash.
 * @len:	size of @data in bytes.
 *
 * Return:	hash value.
 */
static inline size_t fnv1a_bytes_hash(const void *data, size_t len)
{
	const char *bytes = (const char *)data;
	size_t		hash  = fnv_offsetb;

	for (size_t i = 0; i < len; i++) {
		hash ^= bytes[i];
		hash *= fnv_prime;
	}

	return hash;
}

/**
 * fnv1a_str_hash() - fnv1a hash function for nul-terminated strings.
 * @str:	nul-terminated string of characters to hash.
 *
 * Return:	hash value.
 */
static inline size_t fnv1a_str_hash(const char *str)
{
	size_t hash = fnv_offsetb;

	for (size_t i = 0; str[i]; i++) {
		hash ^= str[i];
		hash *= fnv_prime;
	}

	return hash;
}

#endif /* HMAP_HASH_H */