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/* Jody Bruchon's fast hashing function (headers)
* See jody_hash.c for license information */
#ifndef JODY_HASH_H
#define JODY_HASH_H
#ifdef __cplusplus
extern "C" {
#endif
/* Required for uint64_t */
#include <stdint.h>
/* Width of a jody_hash. Changing this will also require
* changing the width of tail masks to match. */
#ifndef JODY_HASH_WIDTH
#define JODY_HASH_WIDTH 64
#endif
/* Version increments when algorithm changes incompatibly */
#define JODY_HASH_VERSION 7
/* DO NOT modify shifts/contants unless you know what you're doing. They were
* chosen after lots of testing. Changes will likely cause lots of hash
* collisions. The vectorized versions also use constants that have this value
* "baked in" which must be updated before using them. */
#ifndef JODY_HASH_SHIFT
#define JODY_HASH_SHIFT 14
#endif
/* The constant value's purpose is to cause each byte in the
* jodyhash_t word to have a positionally dependent variation.
* It is injected into the calculation to prevent a string of
* identical bytes from easily producing an identical hash. */
/* The tail mask table is used for block sizes that are
* indivisible by the width of a jodyhash_t. It is ANDed with the
* final jodyhash_t-sized element to zero out data in the buffer
* that is not part of the data to be hashed. */
/* Set hash parameters based on requested hash width */
#if JODY_HASH_WIDTH == 64
typedef uint64_t jodyhash_t;
#ifndef JODY_HASH_CONSTANT
#define JODY_HASH_CONSTANT 0x71812e0f5463d3c8ULL
#endif
static const jodyhash_t tail_mask[] = {
0x0000000000000000,
0x00000000000000ff,
0x000000000000ffff,
0x0000000000ffffff,
0x00000000ffffffff,
0x000000ffffffffff,
0x0000ffffffffffff,
0x00ffffffffffffff,
0xffffffffffffffff
};
#endif /* JODY_HASH_WIDTH == 64 */
#if JODY_HASH_WIDTH == 32
typedef uint32_t jodyhash_t;
#ifndef JODY_HASH_CONSTANT
#define JODY_HASH_CONSTANT 0x8748ee5dU
#endif
static const jodyhash_t tail_mask[] = {
0x00000000,
0x000000ff,
0x0000ffff,
0x00ffffff,
0xffffffff
};
#endif /* JODY_HASH_WIDTH == 32 */
#if JODY_HASH_WIDTH == 16
typedef uint16_t jodyhash_t;
#ifndef JODY_HASH_CONSTANT
#define JODY_HASH_CONSTANT 0x1f5bU
#endif
static const jodyhash_t tail_mask[] = {
0x0000,
0x00ff,
0xffff
};
#endif /* JODY_HASH_WIDTH == 16 */
/* Double-length shift for double-rotation optimization */
#define JH_SHIFT2 ((JODY_HASH_SHIFT * 2) - (((JODY_HASH_SHIFT * 2) > JODY_HASH_WIDTH) * JODY_HASH_WIDTH))
#define JODY_HASH_CONSTANT_ROR2 (JODY_HASH_CONSTANT >> JH_SHIFT2 | (JODY_HASH_CONSTANT << ((sizeof(jodyhash_t) * 8) - JH_SHIFT2)))
/* Macros for bitwise rotation */
#define JH_ROL(a) (jodyhash_t)((a << JODY_HASH_SHIFT) | (a >> ((sizeof(jodyhash_t) * 8) - JODY_HASH_SHIFT)))
#define JH_ROR(a) (jodyhash_t)((a >> JODY_HASH_SHIFT) | (a << ((sizeof(jodyhash_t) * 8) - JODY_HASH_SHIFT)))
#define JH_ROL2(a) (jodyhash_t)(a << JH_SHIFT2 | (a >> ((sizeof(jodyhash_t) * 8) - JH_SHIFT2)))
#define JH_ROR2(a) (jodyhash_t)(a >> JH_SHIFT2 | (a << ((sizeof(jodyhash_t) * 8) - JH_SHIFT2)))
extern int jody_block_hash(jodyhash_t *data, jodyhash_t *hash, const size_t count);
extern int jody_rolling_block_hash(jodyhash_t *data, jodyhash_t *hash, const size_t count);
#ifdef __cplusplus
}
#endif
#endif /* JODY_HASH_H */
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