// SPDX-License-Identifier: BSD-2-Clause
// Copyright (C) 2010 Andrea Mazzoleni

#include "tommyhash.h"

/******************************************************************************/
/* hash */

#include <string.h> /* for memcpy */

/**
 * Swap endianness.
 * They are needed only if BigEndian.
 */
#if defined(__GNUC__)
#define tommy_swap32(x) __builtin_bswap32(x)
#else
tommy_inline tommy_uint32_t tommy_swap32(tommy_uint32_t v)
{
	return ((v & 0xFF000000) >> 24) |
		((v & 0x00FF0000) >> 8)  |
		((v & 0x0000FF00) << 8)  |
		((v & 0x000000FF) << 24);
}
#endif

tommy_inline tommy_uint32_t tommy_le_uint32_read(const void* ptr)
{
	tommy_uint32_t v;
	memcpy(&v, ptr, sizeof(v));
#if defined(WORDS_BIGENDIAN) || defined(__BIG_ENDIAN__) || \
	(defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
	v = tommy_swap32(v);
#endif
	return v;
}

#define tommy_rot(x, k) \
	(((x) << (k)) | ((x) >> (32 - (k))))

#define tommy_mix(a, b, c) \
	do { \
		a -= c;  a ^= tommy_rot(c, 4);  c += b; \
		b -= a;  b ^= tommy_rot(a, 6);  a += c; \
		c -= b;  c ^= tommy_rot(b, 8);  b += a; \
		a -= c;  a ^= tommy_rot(c, 16);  c += b; \
		b -= a;  b ^= tommy_rot(a, 19);  a += c; \
		c -= b;  c ^= tommy_rot(b, 4);  b += a; \
	} while (0)

#define tommy_final(a, b, c) \
	do { \
		c ^= b; c -= tommy_rot(b, 14); \
		a ^= c; a -= tommy_rot(c, 11); \
		b ^= a; b -= tommy_rot(a, 25); \
		c ^= b; c -= tommy_rot(b, 16); \
		a ^= c; a -= tommy_rot(c, 4);  \
		b ^= a; b -= tommy_rot(a, 14); \
		c ^= b; c -= tommy_rot(b, 24); \
	} while (0)

TOMMY_API tommy_uint32_t tommy_hash_u32(tommy_uint32_t init_val, const void* void_key, tommy_size_t key_len)
{
	const unsigned char* key = tommy_cast(const unsigned char*, void_key);
	tommy_uint32_t a, b, c;

	a = b = c = 0xdeadbeef + ((tommy_uint32_t)key_len) + init_val;

	while (key_len > 12) {
		a += tommy_le_uint32_read(key + 0);
		b += tommy_le_uint32_read(key + 4);
		c += tommy_le_uint32_read(key + 8);

		tommy_mix(a, b, c);

		key_len -= 12;
		key += 12;
	}

	switch (key_len) {
	case 0 :
		return c; /* used only when called with a zero length */
	case 12 :
		c += tommy_le_uint32_read(key + 8);
		b += tommy_le_uint32_read(key + 4);
		a += tommy_le_uint32_read(key + 0);
		break;
	case 11 : c += ((tommy_uint32_t)key[10]) << 16; /* fallthrough */
	case 10 : c += ((tommy_uint32_t)key[9]) << 8; /* fallthrough */
	case 9 : c += key[8]; /* fallthrough */
	case 8 :
		b += tommy_le_uint32_read(key + 4);
		a += tommy_le_uint32_read(key + 0);
		break;
	case 7 : b += ((tommy_uint32_t)key[6]) << 16; /* fallthrough */
	case 6 : b += ((tommy_uint32_t)key[5]) << 8; /* fallthrough */
	case 5 : b += key[4]; /* fallthrough */
	case 4 :
		a += tommy_le_uint32_read(key + 0);
		break;
	case 3 : a += ((tommy_uint32_t)key[2]) << 16; /* fallthrough */
	case 2 : a += ((tommy_uint32_t)key[1]) << 8; /* fallthrough */
	case 1 : a += key[0]; /* fallthrough */
	}

	tommy_final(a, b, c);

	return c;
}

TOMMY_API tommy_uint64_t tommy_hash_u64(tommy_uint64_t init_val, const void* void_key, tommy_size_t key_len)
{
	const unsigned char* key = tommy_cast(const unsigned char*, void_key);
	tommy_uint32_t a, b, c;

	a = b = c = 0xdeadbeef + ((tommy_uint32_t)key_len) + (init_val & 0xffffffff);
	c += init_val >> 32;

	while (key_len > 12) {
		a += tommy_le_uint32_read(key + 0);
		b += tommy_le_uint32_read(key + 4);
		c += tommy_le_uint32_read(key + 8);

		tommy_mix(a, b, c);

		key_len -= 12;
		key += 12;
	}

	switch (key_len) {
	case 0 :
		return c + ((tommy_uint64_t)b << 32); /* used only when called with a zero length */
	case 12 :
		c += tommy_le_uint32_read(key + 8);
		b += tommy_le_uint32_read(key + 4);
		a += tommy_le_uint32_read(key + 0);
		break;
	case 11 : c += ((tommy_uint32_t)key[10]) << 16; /* fallthrough */
	case 10 : c += ((tommy_uint32_t)key[9]) << 8; /* fallthrough */
	case 9 : c += key[8]; /* fallthrough */
	case 8 :
		b += tommy_le_uint32_read(key + 4);
		a += tommy_le_uint32_read(key + 0);
		break;
	case 7 : b += ((tommy_uint32_t)key[6]) << 16; /* fallthrough */
	case 6 : b += ((tommy_uint32_t)key[5]) << 8; /* fallthrough */
	case 5 : b += key[4]; /* fallthrough */
	case 4 :
		a += tommy_le_uint32_read(key + 0);
		break;
	case 3 : a += ((tommy_uint32_t)key[2]) << 16; /* fallthrough */
	case 2 : a += ((tommy_uint32_t)key[1]) << 8; /* fallthrough */
	case 1 : a += key[0]; /* fallthrough */
	}

	tommy_final(a, b, c);

	return c + ((tommy_uint64_t)b << 32);
}

TOMMY_API tommy_uint32_t tommy_strhash_u32(tommy_uint32_t init_val, const void* void_key)
{
	const unsigned char* key = tommy_cast(const unsigned char*, void_key);
	tommy_uint32_t a, b, c;
	tommy_uint32_t m[3] = { 0xff, 0xff00, 0xff0000 };

	a = b = c = 0xdeadbeef + init_val;
	/* this is different than original lookup3 and the result won't match */

	while (1) {
		tommy_uint32_t v = tommy_le_uint32_read(key);

		if (tommy_haszero_u32(v)) {
			if (v & m[0]) {
				a += v & m[0];
				if (v & m[1]) {
					a += v & m[1];
					if (v & m[2])
						a += v & m[2];
				}
			}

			break;
		}

		a += v;

		v = tommy_le_uint32_read(key + 4);

		if (tommy_haszero_u32(v)) {
			if (v & m[0]) {
				b += v & m[0];
				if (v & m[1]) {
					b += v & m[1];
					if (v & m[2])
						b += v & m[2];
				}
			}

			break;
		}

		b += v;

		v = tommy_le_uint32_read(key + 8);

		if (tommy_haszero_u32(v)) {
			if (v & m[0]) {
				c += v & m[0];
				if (v & m[1]) {
					c += v & m[1];
					if (v & m[2])
						c += v & m[2];
				}
			}

			break;
		}

		c += v;

		tommy_mix(a, b, c);

		key += 12;
	}

	/* for lengths that are multipliers of 12 we already have called mix */
	/* this is different than the original lookup3 and the result won't match */

	tommy_final(a, b, c);

	return c;
}