hash-fnv.h File Reference

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Description

Fowler-Noll-Vo Hashes.

FNV is a non-cryptographic hash function created by Glenn Fowler, Landon Curt Noll, and Phong Vo.

Definition in file hash-fnv.h.

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

Macros
#define	HASH_FNV32_BASE   ((uint32_t)2166136261UL)
#define	HASH_FNV32_PRIME   ((uint32_t)16777619UL)
#define	HASH_FNV64_BASE   ((uint64_t)14695981039346656037ULL)
#define	HASH_FNV64_PRIME   ((uint64_t)1099511628211ULL)

Functions
uint32_t	hash_fnv32_retry (uint64_t hash, uint32_t limit)
	reduce hash to be within 0 to limit-1. More...
uint32_t	hash_fnv32_xorfold (uint32_t hash, int bits)
	reduce a hash value to n bits. More...
uint32_t	hash_fnv32a_buf (const void *buf, size_t len, uint32_t hval)
	FNV-1a 32 bit hash over a buffer. More...
uint32_t	hash_fnv32a_strn (const char *str, size_t len, uint32_t hval)
	FNV-1a 32 bit hash over a zero terminated string. More...
uint64_t	hash_fnv64_retry (uint64_t hash, uint64_t limit)
	reduce hash to be within 0 to limit-1. More...
uint64_t	hash_fnv64_xorfold (uint64_t hash, int bits)
	reduce a hash value to n bits. More...
uint64_t	hash_fnv64a_buf (const void *buf, size_t len, uint64_t hval)
	FNV-1a 64 bit hash over a buffer. More...
uint64_t	hash_fnv64a_strn (const char *str, size_t len, uint64_t hval)
	FNV-1a 64 bit hash over a zero terminated string. More...

Function Documentation

hash_fnv64a_buf()

uint64_t hash_fnv64a_buf	(	const void *	buf,
		size_t	len,
		uint64_t	hval
	)

FNV-1a 64 bit hash over a buffer.

Parameters

buf	start of the buffer
len	size of the buffer
hval	previous hash value when incremental hashing or HASH_FNV64_BASE when starting a new hash

Returns

new hash value

Definition at line 38 of file hash-fnv.c.

hash_fnv64a_strn()

uint64_t hash_fnv64a_strn	(	const char *	str,
		size_t	len,
		uint64_t	hval
	)

FNV-1a 64 bit hash over a zero terminated string.

Parameters

str	start of the buffer
len	maximum size to be processed
hval	previous hash value when incremental hashing or HASH_FNV64_BASE when starting a new hash

Returns

new hash value

Definition at line 69 of file hash-fnv.c.

hash_fnv32a_buf()

uint32_t hash_fnv32a_buf	(	const void *	buf,
		size_t	len,
		uint32_t	hval
	)

FNV-1a 32 bit hash over a buffer.

Parameters

buf	start of the buffer
len	size of the buffer
hval	previous hash value when incremental hashing or HASH_FNV32_BASE when starting a new hash

Returns

new hash value

Definition at line 54 of file hash-fnv.c.

hash_fnv32a_strn()

uint32_t hash_fnv32a_strn	(	const char *	str,
		size_t	len,
		uint32_t	hval
	)

FNV-1a 32 bit hash over a zero terminated string.

Parameters

str	start of the buffer
len	maximum size to be processed
hval	previous hash value when incremental hashing or HASH_FNV32_BASE when starting a new hash

Returns

new hash value

Definition at line 85 of file hash-fnv.c.

hash_fnv64_xorfold()

uint64_t hash_fnv64_xorfold	(	uint64_t	hash,
		int	bits
	)

reduce a hash value to n bits.

Uses the xor folding method to stash a hash value together, this preserves unbiased hash distribution

Parameters

hash	result from one of the 64 bit hash functions above
bits	number of significat bits for the result

Returns

hashvalue with no more than 'bits' significant bits

Definition at line 101 of file hash-fnv.c.

hash_fnv32_xorfold()

uint32_t hash_fnv32_xorfold	(	uint32_t	hash,
		int	bits
	)

reduce a hash value to n bits.

Uses the xor folding method to stash a hash value together, this preserves unbiased hash distribution

Parameters

hash	result from one of the 32 bit hash functions above
bits	number of significat bits for the result

Returns

hashvalue with no more than 'bits' significant bits

Definition at line 120 of file hash-fnv.c.

hash_fnv64_retry()

uint64_t hash_fnv64_retry	(	uint64_t	hash,
		uint64_t	limit
	)

reduce hash to be within 0 to limit-1.

Uses the retry method to limit a hash value, this preserves unbiased hash distribution.

Parameters

hash	result from one of the 64 bit hash functions above
limit	upper limit plus one for the result

Returns

hashvalue in the range from 0 to limit-1

Definition at line 139 of file hash-fnv.c.

hash_fnv32_retry()

uint32_t hash_fnv32_retry	(	uint64_t	hash,
		uint32_t	limit
	)

reduce hash to be within 0 to limit-1.

Uses the retry method to limit a hash value, this preserves unbiased hash distribution.

Parameters

hash	result from one of the 32 bit hash functions above
limit	upper limit plus one for the result

Returns

hashvalue in the range from 0 to limit-1

Definition at line 151 of file hash-fnv.c.