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/*
* xxHash - Fast Hash algorithm
* Copyright (C) 2012-2020 Yann Collet
* Copyright (C) 2019-2020 Devin Hussey (easyaspi314)
*
* BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* You can contact the author at :
* - xxHash homepage: http://www.xxhash.com
* - xxHash source repository : https://github.com/Cyan4973/xxHash */
/* This is a compact, 100% standalone reference XXH32 single-run implementation.
* Instead of focusing on performance hacks, this focuses on cleanliness,
* conformance, portability and simplicity.
*
* This file aims to be 100% compatible with C90/C++98, with the additional
* requirement of stdint.h. No library functions are used. */
#include <stddef.h> /* size_t, NULL */
#include <stdint.h> /* uint8_t, uint32_t */
#include "xxhash32.h"
static uint32_t const PRIME32_1 = 0x9E3779B1U; /* 0b10011110001101110111100110110001 */
static uint32_t const PRIME32_2 = 0x85EBCA77U; /* 0b10000101111010111100101001110111 */
static uint32_t const PRIME32_3 = 0xC2B2AE3DU; /* 0b11000010101100101010111000111101 */
static uint32_t const PRIME32_4 = 0x27D4EB2FU; /* 0b00100111110101001110101100101111 */
static uint32_t const PRIME32_5 = 0x165667B1U; /* 0b00010110010101100110011110110001 */
/* Rotates value left by amt. */
static uint32_t XXH_rotl32(uint32_t const value, uint32_t const amt)
{
return (value << (amt % 32)) | (value >> (32 - (amt % 32)));
}
/* Portably reads a 32-bit little endian integer from data at the given offset. */
static uint32_t XXH_read32(uint8_t const *const data, size_t const offset)
{
return (uint32_t) data[offset + 0]
| ((uint32_t) data[offset + 1] << 8)
| ((uint32_t) data[offset + 2] << 16)
| ((uint32_t) data[offset + 3] << 24);
}
/* Mixes input into acc. */
static uint32_t XXH32_round(uint32_t acc, uint32_t const input)
{
acc += input * PRIME32_2;
acc = XXH_rotl32(acc, 13);
acc *= PRIME32_1;
return acc;
}
/* Mixes all bits to finalize the hash. */
static uint32_t XXH32_avalanche(uint32_t hash)
{
hash ^= hash >> 15;
hash *= PRIME32_2;
hash ^= hash >> 13;
hash *= PRIME32_3;
hash ^= hash >> 16;
return hash;
}
/* The XXH32 hash function.
* input: The data to hash.
* length: The length of input. It is undefined behavior to have length larger than the
* capacity of input.
* seed: A 32-bit value to seed the hash with.
* returns: The 32-bit calculated hash value. */
uint32_t XXH32(void const *const input, size_t const length, uint32_t const seed)
{
uint8_t const *const data = (uint8_t const *) input;
uint32_t hash;
size_t remaining = length;
size_t offset = 0;
/* Don't dereference a null pointer. The reference implementation notably doesn't
* check for this by default. */
if (input == NULL) {
return XXH32_avalanche(seed + PRIME32_5);
}
if (remaining >= 16) {
/* Initialize our accumulators */
uint32_t acc1 = seed + PRIME32_1 + PRIME32_2;
uint32_t acc2 = seed + PRIME32_2;
uint32_t acc3 = seed + 0;
uint32_t acc4 = seed - PRIME32_1;
while (remaining >= 16) {
acc1 = XXH32_round(acc1, XXH_read32(data, offset)); offset += 4;
acc2 = XXH32_round(acc2, XXH_read32(data, offset)); offset += 4;
acc3 = XXH32_round(acc3, XXH_read32(data, offset)); offset += 4;
acc4 = XXH32_round(acc4, XXH_read32(data, offset)); offset += 4;
remaining -= 16;
}
hash = XXH_rotl32(acc1, 1) + XXH_rotl32(acc2, 7) + XXH_rotl32(acc3, 12) + XXH_rotl32(acc4, 18);
} else {
/* Not enough data for the main loop, put something in there instead. */
hash = seed + PRIME32_5;
}
hash += (uint32_t) length;
/* Process the remaining data. */
while (remaining >= 4) {
hash += XXH_read32(data, offset) * PRIME32_3;
hash = XXH_rotl32(hash, 17);
hash *= PRIME32_4;
offset += 4;
remaining -= 4;
}
while (remaining != 0) {
hash += (uint32_t) data[offset] * PRIME32_5;
hash = XXH_rotl32(hash, 11);
hash *= PRIME32_1;
--remaining;
++offset;
}
return XXH32_avalanche(hash);
}
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