Hashing

abs_hash provides two classic string-friendly hash algorithms: FNV-1a (32- and 64-bit) and djb2. The hash map module (abs_hashmap) is built on the 64-bit FNV-1a variant for its string keys.

#include "abscom/abs.h"

API

Function	Description
uint32_t abs_hash_fnv1a32(const void *data, size_t len)	FNV-1a 32-bit hash over len bytes.
uint64_t abs_hash_fnv1a64(const void *data, size_t len)	FNV-1a 64-bit hash over len bytes.
uint64_t abs_hash_fnv1a64_str(const char *str)	FNV-1a 64-bit hash of a NUL-terminated string.
uint32_t abs_hash_djb2(const char *str)	djb2 32-bit hash of a NUL-terminated string.

Example

#include "abscom/abs.h"
#include <stdio.h>

int main(void) {
    printf("fnv1a32(\"hello\") = %u\n", abs_hash_fnv1a32("hello", 5));
    printf("fnv1a64(\"hello\") = %llu\n",
           (unsigned long long)abs_hash_fnv1a64_str("hello"));
    printf("djb2(\"hello\")    = %u\n", abs_hash_djb2("hello"));
    return 0;
}

Known test vectors

The test suite pins these values so the algorithms never silently change:

abs_hash_fnv1a32("hello", 5) == 0x4f9f2cabu
abs_hash_djb2("")            == 5381u

Hashing the same bytes always yields the same value; these are not cryptographic hashes, so do not use them for security purposes.

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