#include "rbtdb.h"
/*
 * https://sites.google.com/site/murmurhash/
 *
 * MurmurHash3 was written by Austin Appleby, and is placed in the public
 * domain. The author hereby disclaims copyright to this source code.
 *
 * Eric Wong trivially ported this to C for Ruby tdb (32-bit versions only)
 */

#include <stdint.h>

static inline uint32_t rotl32(uint32_t x, int8_t r)
{
	return (x << r) | (x >> (32 - r));
}

#define	ROTL32(x,y)	rotl32(x,y)

#define BIG_CONSTANT(x) (x##LLU)

/* ----------------------------------------------------------------------------
 * Block read - if your platform needs to do endian-swapping or can only
 * handle aligned reads, do the conversion here
 */

static inline uint32_t getblock(const uint32_t * p, int i)
{
	return p[i];
}

/* ----------------------------------------------------------------------------
 * Finalization mix - force all bits of a hash block to avalanche
 */

static inline uint32_t fmix(uint32_t h)
{
	h ^= h >> 16;
	h *= 0x85ebca6b;
	h ^= h >> 13;
	h *= 0xc2b2ae35;
	h ^= h >> 16;

	return h;
}

unsigned int rbtdb_murmur3a(TDB_DATA * key)
{
	const uint8_t *data = key->dptr;
	int len = (int)key->dsize;
	const int nblocks = len / 4;
	static const uint32_t seed;
	uint32_t h1 = seed;
	int i;

	static const uint32_t c1 = 0xcc9e2d51;
	static const uint32_t c2 = 0x1b873593;

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

	for (i = -nblocks; i; i++) {
		uint32_t k1 = getblock(blocks, i);

		k1 *= c1;
		k1 = ROTL32(k1, 15);
		k1 *= c2;

		h1 ^= k1;
		h1 = ROTL32(h1, 13);
		h1 = h1 * 5 + 0xe6546b64;
	}

	/* tail */
	{
		const uint8_t *tail = (const uint8_t *)(data + nblocks * 4);
		uint32_t k1 = 0;

		switch (len & 3) {
		case 3:
			k1 ^= tail[2] << 16;
		case 2:
			k1 ^= tail[1] << 8;
		case 1:
			k1 ^= tail[0];
			k1 *= c1;
			k1 = ROTL32(k1, 15);
			k1 *= c2;
			h1 ^= k1;
		};
	}

	/* finalization */

	h1 ^= len;

	return fmix(h1);
}

static inline uint64_t rotl64(uint64_t x, int8_t r)
{
	return (x << r) | (x >> (64 - r));
}

#define ROTL64(x,y)	rotl64(x,y)

static inline uint64_t getblock64(const uint64_t * p, int i)
{
	return p[i];
}

static inline uint64_t fmix64(uint64_t k)
{
	k ^= k >> 33;
	k *= BIG_CONSTANT(0xff51afd7ed558ccd);
	k ^= k >> 33;
	k *= BIG_CONSTANT(0xc4ceb9fe1a85ec53);
	k ^= k >> 33;

	return k;
}

/* this was a 128-bit hash for x86_64, but we only want 32-bits */
unsigned int rbtdb_murmur3f(TDB_DATA * key)
{
	const uint8_t *data = key->dptr;
	int len = (int)key->dsize;
	const int nblocks = len / 16;
	static const uint32_t seed;
	uint64_t h1 = seed;
	uint64_t h2 = seed;
	uint64_t c1 = BIG_CONSTANT(0x87c37b91114253d5);
	uint64_t c2 = BIG_CONSTANT(0x4cf5ad432745937f);
	int i;

	/* body */
	const uint64_t *blocks = (const uint64_t *)(data);

	for (i = 0; i < nblocks; i++) {
		uint64_t k1 = getblock64(blocks, i * 2 + 0);
		uint64_t k2 = getblock64(blocks, i * 2 + 1);

		k1 *= c1;
		k1 = ROTL64(k1, 31);
		k1 *= c2;
		h1 ^= k1;

		h1 = ROTL64(h1, 27);
		h1 += h2;
		h1 = h1 * 5 + 0x52dce729;

		k2 *= c2;
		k2 = ROTL64(k2, 33);
		k2 *= c1;
		h2 ^= k2;

		h2 = ROTL64(h2, 31);
		h2 += h1;
		h2 = h2 * 5 + 0x38495ab5;
	}

	/* tail */
	{
		const uint8_t *tail = (const uint8_t *)(data + nblocks * 16);

		uint64_t k1 = 0;
		uint64_t k2 = 0;
		#define CAST64(x) ((uint64_t)(x))

		switch (len & 15) {
		case 15:
			k2 ^= CAST64(tail[14]) << 48;
		case 14:
			k2 ^= CAST64(tail[13]) << 40;
		case 13:
			k2 ^= CAST64(tail[12]) << 32;
		case 12:
			k2 ^= CAST64(tail[11]) << 24;
		case 11:
			k2 ^= CAST64(tail[10]) << 16;
		case 10:
			k2 ^= CAST64(tail[9]) << 8;
		case 9:
			k2 ^= CAST64(tail[8]) << 0;
			k2 *= c2;
			k2 = ROTL64(k2, 33);
			k2 *= c1;
			h2 ^= k2;

		case 8:
			k1 ^= CAST64(tail[7]) << 56;
		case 7:
			k1 ^= CAST64(tail[6]) << 48;
		case 6:
			k1 ^= CAST64(tail[5]) << 40;
		case 5:
			k1 ^= CAST64(tail[4]) << 32;
		case 4:
			k1 ^= CAST64(tail[3]) << 24;
		case 3:
			k1 ^= CAST64(tail[2]) << 16;
		case 2:
			k1 ^= CAST64(tail[1]) << 8;
		case 1:
			k1 ^= CAST64(tail[0]) << 0;
			k1 *= c1;
			k1 = ROTL64(k1, 31);
			k1 *= c2;
			h1 ^= k1;
		};
	}

	/* finalization */

	h1 ^= len;
	h2 ^= len;

	h1 += h2;
	h2 += h1;

	h1 = fmix64(h1);
	h2 = fmix64(h2);

	h1 += h2;

	/* not needed for 32-bit hash */
	/* h2 += h1; */

	return (unsigned int)h1; /* truncate to 32-bits */
}