/**

 * Seccomp Library hash code

 *

 */

/*

 * This code is based on MurmurHash3.cpp from Austin Appleby and is placed in

 * the public domain.

 *

 * https://github.com/aappleby/smhasher

 *

 */

#include <stdlib.h>

#include <inttypes.h>

#include "hash.h"

static inline uint32_t getblock32(const uint32_t *p, int i)

{

	return p[i];

}

static inline uint32_t rotl32(uint32_t x, int8_t r)

{

	return (x << r) | (x >> (32 - r));

}

static inline uint32_t fmix32(uint32_t h)

{

	h ^= h >> 16;

	h *= 0x85ebca6b;

	h ^= h >> 13;

	h *= 0xc2b2ae35;

	h ^= h >> 16;

	return h;

}

/* NOTE: this is an implementation of MurmurHash3_x86_32 */

uint32_t hash(const void *key, size_t length)

{

	const uint8_t *data = (const uint8_t *)key;

	const uint32_t *blocks;

	const uint8_t *tail;

	const int nblocks = length / 4;

	const uint32_t c1 = 0xcc9e2d51;

	const uint32_t c2 = 0x1b873593;

	uint32_t k1;

	uint32_t k2 = 0;

	int i;

	/* NOTE: we always force a seed of 0 */

	uint32_t h1 = 0;

	/* body */

	blocks = (const uint32_t *)(data + nblocks * 4);

	for(i = -nblocks; i; i++) {

		k1 = getblock32(blocks, i);

		k1 *= c1;

		k1 = rotl32(k1, 15);

		k1 *= c2;

		h1 ^= k1;

		h1 = rotl32(h1, 13);

		h1 = h1 * 5 + 0xe6546b64;

	}

	/* tail */

	tail = (const uint8_t *)(data + nblocks * 4);

	switch(length & 3) {

	case 3:

		k2 ^= tail[2] << 16;

	case 2:

		k2 ^= tail[1] << 8;

	case 1:

		k2 ^= tail[0];

		k2 *= c1;

		k2 = rotl32(k2, 15);

		k2 *= c2;

		h1 ^= k2;

	};

	/* finalization */

	h1 ^= length;

	h1 = fmix32(h1);

	return h1;

}