/*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2015 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
#ifndef FOLLY_BASE_HASH_H_
#define FOLLY_BASE_HASH_H_
+#include <cstdint>
#include <cstring>
-#include <stdint.h>
#include <string>
-#include <utility>
#include <tuple>
+#include <type_traits>
+#include <utility>
-#include "folly/SpookyHashV1.h"
-#include "folly/SpookyHashV2.h"
+#include <folly/ApplyTuple.h>
+#include <folly/SpookyHashV1.h>
+#include <folly/SpookyHashV2.h>
/*
* Various hashing functions.
// 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) {
+inline uint64_t hash_128_to_64(const uint64_t upper, const uint64_t lower) {
// Murmur-inspired hashing.
- const size_t kMul = 0x9ddfea08eb382d69ULL;
- size_t a = (lower ^ upper) * kMul;
+ const uint64_t kMul = 0x9ddfea08eb382d69ULL;
+ uint64_t a = (lower ^ upper) * kMul;
a ^= (a >> 47);
- size_t b = (upper ^ a) * kMul;
+ uint64_t b = (upper ^ a) * kMul;
b ^= (b >> 47);
b *= kMul;
return b;
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;
+}
+
+inline uint32_t twang_32from64(uint64_t key);
+
template <class Hasher, typename T, typename... Ts>
size_t hash_combine_generic(const T& t, const Ts&... ts) {
size_t seed = Hasher::hash(t);
return seed;
}
size_t remainder = hash_combine_generic<Hasher>(ts...);
- return hash_128_to_64(seed, remainder);
+ /* static */ if (sizeof(size_t) == sizeof(uint32_t)) {
+ return twang_32from64((uint64_t(seed) << 32) | remainder);
+ } else {
+ return static_cast<size_t>(hash_128_to_64(seed, remainder));
+ }
}
// Simply uses std::hash to hash. Note that std::hash is not guaranteed
}
inline uint32_t fnv32_buf(const void* buf,
- int n,
+ size_t n,
uint32_t hash = FNV_32_HASH_START) {
- const char* char_buf = reinterpret_cast<const char*>(buf);
+ // forcing signed char, since other platforms can use unsigned
+ const signed char* char_buf = reinterpret_cast<const signed char*>(buf);
- for (int i = 0; i < n; ++i) {
+ for (size_t i = 0; i < n; ++i) {
hash += (hash << 1) + (hash << 4) + (hash << 7) +
(hash << 8) + (hash << 24);
hash ^= char_buf[i];
}
inline uint64_t fnv64_buf(const void* buf,
- int n,
+ size_t n,
uint64_t hash = FNV_64_HASH_START) {
- const char* char_buf = reinterpret_cast<const char*>(buf);
+ // forcing signed char, since other platforms can use unsigned
+ const signed char* char_buf = reinterpret_cast<const signed char*>(buf);
- for (int i = 0; i < n; ++i) {
+ 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];
#define get16bits(d) (*((const uint16_t*) (d)))
-inline uint32_t hsieh_hash32_buf(const void* buf, int len) {
- const char* s = reinterpret_cast<const char*>(buf);
- uint32_t hash = len;
+inline uint32_t hsieh_hash32_buf(const void* buf, size_t len) {
+ // forcing signed char, since other platforms can use unsigned
+ const signed char* s = reinterpret_cast<const signed char*>(buf);
+ uint32_t hash = static_cast<uint32_t>(len);
uint32_t tmp;
- int rem;
+ size_t rem;
if (len <= 0 || buf == 0) {
return 0;
} // namespace hash
-template<class Key>
+template<class Key, class Enable = void>
struct hasher;
+struct Hash {
+ template <class T>
+ size_t operator()(const T& v) const {
+ return hasher<T>()(v);
+ }
+
+ template <class T, class... Ts>
+ size_t operator()(const T& t, const Ts&... ts) const {
+ return hash::hash_128_to_64((*this)(t), (*this)(ts...));
+ }
+};
+
template<> struct hasher<int32_t> {
size_t operator()(int32_t key) const {
return hash::jenkins_rev_mix32(uint32_t(key));
template<> struct hasher<int64_t> {
size_t operator()(int64_t key) const {
- return hash::twang_mix64(uint64_t(key));
+ return static_cast<size_t>(hash::twang_mix64(uint64_t(key)));
}
};
template<> struct hasher<uint64_t> {
size_t operator()(uint64_t key) const {
- return hash::twang_mix64(key);
+ return static_cast<size_t>(hash::twang_mix64(key));
+ }
+};
+
+template<> struct hasher<std::string> {
+ size_t operator()(const std::string& key) const {
+ return static_cast<size_t>(
+ hash::SpookyHashV2::Hash64(key.data(), key.size(), 0));
+ }
+};
+
+template <class T>
+struct hasher<T, typename std::enable_if<std::is_enum<T>::value, void>::type> {
+ size_t operator()(T key) const {
+ return Hash()(static_cast<typename std::underlying_type<T>::type>(key));
+ }
+};
+
+template <class T1, class T2>
+struct hasher<std::pair<T1, T2>> {
+ size_t operator()(const std::pair<T1, T2>& key) const {
+ return Hash()(key.first, key.second);
+ }
+};
+
+template <typename... Ts>
+struct hasher<std::tuple<Ts...>> {
+ size_t operator() (const std::tuple<Ts...>& key) const {
+ return applyTuple(Hash(), key);
}
};
// Hash function for pairs. Requires default hash functions for both
// items in the pair.
template <typename T1, typename T2>
- class hash<std::pair<T1, 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);