xxhash is a fast, high-quality hashing function. The appended brings in the 32-bit version of it, with the small modification that it assumes the data to be hashed is made of 32-bit chunks; this increases speed slightly for the use-case we care about, i.e. tb-hash.
The original algorithm, as well as a 64-bit implementation, can be found at: https://github.com/Cyan4973/xxHash Signed-off-by: Emilio G. Cota <c...@braap.org> --- include/qemu/xxhash.h | 106 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 106 insertions(+) create mode 100644 include/qemu/xxhash.h diff --git a/include/qemu/xxhash.h b/include/qemu/xxhash.h new file mode 100644 index 0000000..a13a665 --- /dev/null +++ b/include/qemu/xxhash.h @@ -0,0 +1,106 @@ +/* + * xxHash - Fast Hash algorithm + * Copyright (C) 2012-2016, Yann Collet + * + * 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 source repository : https://github.com/Cyan4973/xxHash + */ +#ifndef QEMU_XXHASH_H +#define QEMU_XXHASH_H + +#define PRIME32_1 2654435761U +#define PRIME32_2 2246822519U +#define PRIME32_3 3266489917U +#define PRIME32_4 668265263U +#define PRIME32_5 374761393U + +/* + * Note : although _rotl exists for minGW (GCC under windows), performance + * seems poor. + */ +#if defined(_MSC_VER) +# define XXH_rotl32(x, r) _rotl(x, r) +#else +# define XXH_rotl32(x, r) ((x << r) | (x >> (32 - r))) +#endif + +/* u32 hash of @n contiguous chunks of u32's */ +static inline uint32_t qemu_xxh32(const uint32_t *p, size_t n, uint32_t seed) +{ + const uint32_t *end = p + n; + uint32_t h32; + + if (n >= 4) { + const uint32_t * const limit = end - 4; + uint32_t v1 = seed + PRIME32_1 + PRIME32_2; + uint32_t v2 = seed + PRIME32_2; + uint32_t v3 = seed + 0; + uint32_t v4 = seed - PRIME32_1; + + do { + v1 += *p * PRIME32_2; + v1 = XXH_rotl32(v1, 13); + v1 *= PRIME32_1; + p++; + v2 += *p * PRIME32_2; + v2 = XXH_rotl32(v2, 13); + v2 *= PRIME32_1; + p++; + v3 += *p * PRIME32_2; + v3 = XXH_rotl32(v3, 13); + v3 *= PRIME32_1; + p++; + v4 += *p * PRIME32_2; + v4 = XXH_rotl32(v4, 13); + v4 *= PRIME32_1; + p++; + } while (p <= limit); + h32 = XXH_rotl32(v1, 1) + XXH_rotl32(v2, 7) + XXH_rotl32(v3, 12) + + XXH_rotl32(v4, 18); + } else { + h32 = seed + PRIME32_5; + } + + h32 += n * sizeof(uint32_t); + + while (p < end) { + h32 += *p * PRIME32_3; + h32 = XXH_rotl32(h32, 17) * PRIME32_4 ; + p++; + } + + h32 ^= h32 >> 15; + h32 *= PRIME32_2; + h32 ^= h32 >> 13; + h32 *= PRIME32_3; + h32 ^= h32 >> 16; + + return h32; +} + +#endif /* QEMU_XXHASH_H */ -- 2.5.0
