hash_function.h

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/*
 * Copyright (c) 2022 Meta
 *
 * SPDX-License-Identifier: Apache-2.0
 */

 
#ifndef ZEPHYR_INCLUDE_SYS_HASH_FUNCTION_H_
#define ZEPHYR_INCLUDE_SYS_HASH_FUNCTION_H_
 
#include <stddef.h>
#include <stdint.h>
 
#include <zephyr/sys/__assert.h>
#include <zephyr/sys/util_macro.h>
 
#ifdef __cplusplus
extern "C" {
#endif


typedef uint32_t (*sys_hash_func32_t)(const void *str, size_t n);

static inline uint32_t sys_hash32_identity(const void *str, size_t n)
{
        switch (n) {
        case sizeof(uint8_t):
                return *(uint8_t *)str;
        case sizeof(uint16_t):
                return *(uint16_t *)str;
        case sizeof(uint32_t):
                return *(uint32_t *)str;
        case sizeof(uint64_t):
                return (uint32_t)(*(uint64_t *)str);
        default:
                break;
        }
 
        __ASSERT(false, "invalid str length %zu", n);
 
        return 0;
}

uint32_t sys_hash32_djb2(const void *str, size_t n);

uint32_t sys_hash32_murmur3(const void *str, size_t n);

static inline uint32_t sys_hash32(const void *str, size_t n)
{
        if (IS_ENABLED(CONFIG_SYS_HASH_FUNC32_CHOICE_IDENTITY)) {
                return sys_hash32_identity(str, n);
        }
 
        if (IS_ENABLED(CONFIG_SYS_HASH_FUNC32_CHOICE_DJB2)) {
                return sys_hash32_djb2(str, n);
        }
 
        if (IS_ENABLED(CONFIG_SYS_HASH_FUNC32_CHOICE_MURMUR3)) {
                return sys_hash32_murmur3(str, n);
        }
 
        __ASSERT(0, "No default 32-bit hash. See CONFIG_SYS_HASH_FUNC32_CHOICE");
 
        return 0;
}

 
#ifdef __cplusplus
}
#endif
 
#endif /* ZEPHYR_INCLUDE_SYS_HASH_FUNCTION_H_ */