/*
- * Copyright 2014 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.
* limitations under the License.
*/
-#ifndef FOLLY_BASE_HASH_H_
-#define FOLLY_BASE_HASH_H_
+#pragma once
-#include <cstring>
-#include <stdint.h>
-#include <string>
-#include <utility>
-#include <tuple>
-
-#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<T>; 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 uint64_t hash_128_to_64(const uint64_t upper, const uint64_t lower) {
- // Murmur-inspired hashing.
- const uint64_t kMul = 0x9ddfea08eb382d69ULL;
- uint64_t a = (lower ^ upper) * kMul;
- a ^= (a >> 47);
- uint64_t b = (upper ^ a) * kMul;
- b ^= (b >> 47);
- b *= kMul;
- return b;
-}
-
-// Never used, but gcc demands it.
-template <class Hasher>
-inline size_t hash_combine_generic() {
- return 0;
-}
-
-template <
- class Iter,
- class Hash = std::hash<typename std::iterator_traits<Iter>::value_type>>
-uint64_t hash_range(Iter begin,
- Iter end,
- uint64_t hash = 0,
- Hash hasher = Hash()) {
- for (; begin != end; ++begin) {
- hash = hash_128_to_64(hash, hasher(*begin));
- }
- return hash;
-}
-
-template <class Hasher, typename T, typename... Ts>
-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<Hasher>(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 <typename T>
- static size_t hash(const T& t) {
- return std::hash<T>()(t);
- }
-};
-
-template <typename T, typename... Ts>
-size_t hash_combine(const T& t, const Ts&... ts) {
- return hash_combine_generic<StdHasher>(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 = 2166136261UL;
-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,
- size_t n,
- uint32_t hash = FNV_32_HASH_START) {
- const char* char_buf = reinterpret_cast<const char*>(buf);
-
- for (size_t 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,
- uint32_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,
- size_t n,
- uint64_t hash = FNV_64_HASH_START) {
- const char* char_buf = reinterpret_cast<const char*>(buf);
-
- for (size_t 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, size_t len) {
- const char* s = reinterpret_cast<const char*>(buf);
- uint32_t hash = static_cast<uint32_t>(len);
- uint32_t tmp;
- size_t 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<class Key>
-struct hasher;
-
-template<> struct hasher<int32_t> {
- size_t operator()(int32_t key) const {
- return hash::jenkins_rev_mix32(uint32_t(key));
- }
-};
-
-template<> struct hasher<uint32_t> {
- size_t operator()(uint32_t key) const {
- return hash::jenkins_rev_mix32(key);
- }
-};
-
-template<> struct hasher<int64_t> {
- size_t operator()(int64_t key) const {
- return hash::twang_mix64(uint64_t(key));
- }
-};
-
-template<> struct hasher<uint64_t> {
- size_t operator()(uint64_t key) const {
- return hash::twang_mix64(key);
- }
-};
-
-// recursion
-template <size_t index, typename... Ts>
-struct TupleHasher {
- size_t operator()(std::tuple<Ts...> const& key) const {
- return hash::hash_combine(
- TupleHasher<index - 1, Ts...>()(key),
- std::get<index>(key));
- }
-};
-
-// base
-template <typename... Ts>
-struct TupleHasher<0, Ts...> {
- size_t operator()(std::tuple<Ts...> 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 <typename T1, typename T2>
- struct hash<std::pair<T1, T2> > {
- public:
- size_t operator()(const std::pair<T1, T2>& x) const {
- return folly::hash::hash_combine(x.first, x.second);
- }
- };
-
- // Hash function for tuples. Requires default hash functions for all types.
- template <typename... Ts>
- struct hash<std::tuple<Ts...>> {
- size_t operator()(std::tuple<Ts...> const& key) const {
- folly::TupleHasher<
- std::tuple_size<std::tuple<Ts...>>::value - 1, // start index
- Ts...> hasher;
-
- return hasher(key);
- }
- };
-} // namespace std
-
-#endif
+// shims:
+#include <folly/hash/Hash.h>
projects / folly.git / blobdiff