X-Git-Url: http://plrg.eecs.uci.edu/git/?p=folly.git;a=blobdiff_plain;f=folly%2FHash.h;h=916dfba81436f2f9c0d2aaa540fbe17b76e22912;hp=cbd07b56ba126cd81efceb2ef1684f1944c87f12;hb=2d3c33462242cada87a857143101cd99cd94b8f8;hpb=b71e31a5fe51724cd9b05fbb4bbf87510f01e45f diff --git a/folly/Hash.h b/folly/Hash.h index cbd07b56..916dfba8 100644 --- a/folly/Hash.h +++ b/folly/Hash.h @@ -1,5 +1,5 @@ /* - * Copyright 2013 Facebook, Inc. + * Copyright 2017 Facebook, Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. @@ -14,386 +14,7 @@ * limitations under the License. */ -#ifndef FOLLY_BASE_HASH_H_ -#define FOLLY_BASE_HASH_H_ +#pragma once -#include -#include -#include -#include -#include - -#include "folly/SpookyHashV1.h" -#include "folly/SpookyHashV2.h" - -/* - * Various hashing functions. - */ - -namespace folly { namespace hash { - -// This is a general-purpose way to create a single hash from multiple -// hashable objects. hash_combine_generic takes a class Hasher implementing -// hash; hash_combine uses a default hasher StdHasher that uses std::hash. -// hash_combine_generic hashes each argument and combines those hashes in -// an order-dependent way to yield a new hash. - - -// This is the Hash128to64 function from Google's cityhash (available -// under the MIT License). We use it to reduce multiple 64 bit hashes -// into a single hash. -inline size_t hash_128_to_64(const size_t upper, const size_t lower) { - // Murmur-inspired hashing. - const size_t kMul = 0x9ddfea08eb382d69ULL; - size_t a = (lower ^ upper) * kMul; - a ^= (a >> 47); - size_t b = (upper ^ a) * kMul; - b ^= (b >> 47); - b *= kMul; - return b; -} - -// Never used, but gcc demands it. -template -inline size_t hash_combine_generic() { - return 0; -} - -template -size_t hash_combine_generic(const T& t, const Ts&... ts) { - size_t seed = Hasher::hash(t); - if (sizeof...(ts) == 0) { - return seed; - } - size_t remainder = hash_combine_generic(ts...); - return hash_128_to_64(seed, remainder); -} - -// Simply uses std::hash to hash. Note that std::hash is not guaranteed -// to be a very good hash function; provided std::hash doesn't collide on -// the individual inputs, you are fine, but that won't be true for, say, -// strings or pairs -class StdHasher { - public: - template - static size_t hash(const T& t) { - return std::hash()(t); - } -}; - -template -size_t hash_combine(const T& t, const Ts&... ts) { - return hash_combine_generic(t, ts...); -} - -////////////////////////////////////////////////////////////////////// - -/* - * Thomas Wang 64 bit mix hash function - */ - -inline uint64_t twang_mix64(uint64_t key) { - key = (~key) + (key << 21); // key *= (1 << 21) - 1; key -= 1; - key = key ^ (key >> 24); - key = key + (key << 3) + (key << 8); // key *= 1 + (1 << 3) + (1 << 8) - key = key ^ (key >> 14); - key = key + (key << 2) + (key << 4); // key *= 1 + (1 << 2) + (1 << 4) - key = key ^ (key >> 28); - key = key + (key << 31); // key *= 1 + (1 << 31) - return key; -} - -/* - * Inverse of twang_mix64 - * - * Note that twang_unmix64 is significantly slower than twang_mix64. - */ - -inline uint64_t twang_unmix64(uint64_t key) { - // See the comments in jenkins_rev_unmix32 for an explanation as to how this - // was generated - key *= 4611686016279904257U; - key ^= (key >> 28) ^ (key >> 56); - key *= 14933078535860113213U; - key ^= (key >> 14) ^ (key >> 28) ^ (key >> 42) ^ (key >> 56); - key *= 15244667743933553977U; - key ^= (key >> 24) ^ (key >> 48); - key = (key + 1) * 9223367638806167551U; - return key; -} - -/* - * Thomas Wang downscaling hash function - */ - -inline uint32_t twang_32from64(uint64_t key) { - key = (~key) + (key << 18); - key = key ^ (key >> 31); - key = key * 21; - key = key ^ (key >> 11); - key = key + (key << 6); - key = key ^ (key >> 22); - return (uint32_t) key; -} - -/* - * Robert Jenkins' reversible 32 bit mix hash function - */ - -inline uint32_t jenkins_rev_mix32(uint32_t key) { - key += (key << 12); // key *= (1 + (1 << 12)) - key ^= (key >> 22); - key += (key << 4); // key *= (1 + (1 << 4)) - key ^= (key >> 9); - key += (key << 10); // key *= (1 + (1 << 10)) - key ^= (key >> 2); - // key *= (1 + (1 << 7)) * (1 + (1 << 12)) - key += (key << 7); - key += (key << 12); - return key; -} - -/* - * Inverse of jenkins_rev_mix32 - * - * Note that jenkinks_rev_unmix32 is significantly slower than - * jenkins_rev_mix32. - */ - -inline uint32_t jenkins_rev_unmix32(uint32_t key) { - // These are the modular multiplicative inverses (in Z_2^32) of the - // multiplication factors in jenkins_rev_mix32, in reverse order. They were - // computed using the Extended Euclidean algorithm, see - // http://en.wikipedia.org/wiki/Modular_multiplicative_inverse - key *= 2364026753U; - - // The inverse of a ^= (a >> n) is - // b = a - // for (int i = n; i < 32; i += n) { - // b ^= (a >> i); - // } - key ^= - (key >> 2) ^ (key >> 4) ^ (key >> 6) ^ (key >> 8) ^ - (key >> 10) ^ (key >> 12) ^ (key >> 14) ^ (key >> 16) ^ - (key >> 18) ^ (key >> 20) ^ (key >> 22) ^ (key >> 24) ^ - (key >> 26) ^ (key >> 28) ^ (key >> 30); - key *= 3222273025U; - key ^= (key >> 9) ^ (key >> 18) ^ (key >> 27); - key *= 4042322161U; - key ^= (key >> 22); - key *= 16773121U; - return key; -} - -/* - * Fowler / Noll / Vo (FNV) Hash - * http://www.isthe.com/chongo/tech/comp/fnv/ - */ - -const uint32_t FNV_32_HASH_START = 216613626UL; -const uint64_t FNV_64_HASH_START = 14695981039346656037ULL; - -inline uint32_t fnv32(const char* s, - uint32_t hash = FNV_32_HASH_START) { - for (; *s; ++s) { - hash += (hash << 1) + (hash << 4) + (hash << 7) + - (hash << 8) + (hash << 24); - hash ^= *s; - } - return hash; -} - -inline uint32_t fnv32_buf(const void* buf, - int n, - uint32_t hash = FNV_32_HASH_START) { - const char* char_buf = reinterpret_cast(buf); - - for (int i = 0; i < n; ++i) { - hash += (hash << 1) + (hash << 4) + (hash << 7) + - (hash << 8) + (hash << 24); - hash ^= char_buf[i]; - } - - return hash; -} - -inline uint32_t fnv32(const std::string& str, - uint64_t hash = FNV_32_HASH_START) { - return fnv32_buf(str.data(), str.size(), hash); -} - -inline uint64_t fnv64(const char* s, - uint64_t hash = FNV_64_HASH_START) { - for (; *s; ++s) { - hash += (hash << 1) + (hash << 4) + (hash << 5) + (hash << 7) + - (hash << 8) + (hash << 40); - hash ^= *s; - } - return hash; -} - -inline uint64_t fnv64_buf(const void* buf, - int n, - uint64_t hash = FNV_64_HASH_START) { - const char* char_buf = reinterpret_cast(buf); - - for (int i = 0; i < n; ++i) { - hash += (hash << 1) + (hash << 4) + (hash << 5) + (hash << 7) + - (hash << 8) + (hash << 40); - hash ^= char_buf[i]; - } - return hash; -} - -inline uint64_t fnv64(const std::string& str, - uint64_t hash = FNV_64_HASH_START) { - return fnv64_buf(str.data(), str.size(), hash); -} - -/* - * Paul Hsieh: http://www.azillionmonkeys.com/qed/hash.html - */ - -#define get16bits(d) (*((const uint16_t*) (d))) - -inline uint32_t hsieh_hash32_buf(const void* buf, int len) { - const char* s = reinterpret_cast(buf); - uint32_t hash = len; - uint32_t tmp; - int rem; - - if (len <= 0 || buf == 0) { - return 0; - } - - rem = len & 3; - len >>= 2; - - /* Main loop */ - for (;len > 0; len--) { - hash += get16bits (s); - tmp = (get16bits (s+2) << 11) ^ hash; - hash = (hash << 16) ^ tmp; - s += 2*sizeof (uint16_t); - hash += hash >> 11; - } - - /* Handle end cases */ - switch (rem) { - case 3: - hash += get16bits(s); - hash ^= hash << 16; - hash ^= s[sizeof (uint16_t)] << 18; - hash += hash >> 11; - break; - case 2: - hash += get16bits(s); - hash ^= hash << 11; - hash += hash >> 17; - break; - case 1: - hash += *s; - hash ^= hash << 10; - hash += hash >> 1; - } - - /* Force "avalanching" of final 127 bits */ - hash ^= hash << 3; - hash += hash >> 5; - hash ^= hash << 4; - hash += hash >> 17; - hash ^= hash << 25; - hash += hash >> 6; - - return hash; -}; - -#undef get16bits - -inline uint32_t hsieh_hash32(const char* s) { - return hsieh_hash32_buf(s, std::strlen(s)); -} - -inline uint32_t hsieh_hash32_str(const std::string& str) { - return hsieh_hash32_buf(str.data(), str.size()); -} - -////////////////////////////////////////////////////////////////////// - -} // namespace hash - -template -struct hasher; - -template<> struct hasher { - size_t operator()(int32_t key) const { - return hash::jenkins_rev_mix32(uint32_t(key)); - } -}; - -template<> struct hasher { - size_t operator()(uint32_t key) const { - return hash::jenkins_rev_mix32(key); - } -}; - -template<> struct hasher { - size_t operator()(int64_t key) const { - return hash::twang_mix64(uint64_t(key)); - } -}; - -template<> struct hasher { - size_t operator()(uint64_t key) const { - return hash::twang_mix64(key); - } -}; - -// recursion -template -struct TupleHasher { - size_t operator()(std::tuple const& key) const { - return hash::hash_combine( - TupleHasher()(key), - std::get(key)); - } -}; - -// base -template -struct TupleHasher<0, Ts...> { - size_t operator()(std::tuple const& key) const { - // we could do std::hash here directly, but hash_combine hides all the - // ugly templating implicitly - return hash::hash_combine(std::get<0>(key)); - } -}; - -} // namespace folly - -// Custom hash functions. -namespace std { - // Hash function for pairs. Requires default hash functions for both - // items in the pair. - template - class hash > { - public: - size_t operator()(const std::pair& x) const { - return folly::hash::hash_combine(x.first, x.second); - } - }; - - // Hash function for tuples. Requires default hash functions for all types. - template - struct hash> { - size_t operator()(std::tuple const& key) const { - folly::TupleHasher< - std::tuple_size>::value - 1, // start index - Ts...> hasher; - - return hasher(key); - } - }; -} // namespace std - -#endif +// shims: +#include