X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=folly%2FHash.h;h=b0ae03bb764bbb3e9e0034c75969f896258c5900;hb=c1dd3ab18408c97e52856f11d135dcb3237f29b4;hp=a52da9c634e6ff0206b17e327b852896281ed786;hpb=27494a20393fa45072e7d526d358835f3abe312a;p=folly.git

diff --git a/folly/Hash.h b/folly/Hash.h
index a52da9c6..b0ae03bb 100644
--- a/folly/Hash.h
+++ b/folly/Hash.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012 Facebook, Inc.
+ * Copyright 2016 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,12 +14,19 @@
  * limitations under the License.
  */
 
-#ifndef FOLLY_BASE_HASH_H_
-#define FOLLY_BASE_HASH_H_
+#pragma once
 
-#include <stdint.h>
+#include <cstdint>
 #include <cstring>
 #include <string>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include <folly/ApplyTuple.h>
+#include <folly/Bits.h>
+#include <folly/SpookyHashV1.h>
+#include <folly/SpookyHashV2.h>
 
 /*
  * Various hashing functions.
@@ -27,6 +34,79 @@
 
 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;
+}
+
+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);
+  if (sizeof...(ts) == 0) {
+    return seed;
+  }
+  size_t remainder = hash_combine_generic<Hasher>(ts...);
+  /* 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
+// 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...);
+}
+
 //////////////////////////////////////////////////////////////////////
 
 /*
@@ -34,13 +114,32 @@ namespace folly { namespace hash {
  */
 
 inline uint64_t twang_mix64(uint64_t key) {
-  key = (~key) + (key << 21);
+  key = (~key) + (key << 21);  // key *= (1 << 21) - 1; key -= 1;
   key = key ^ (key >> 24);
-  key = (key + (key << 3)) + (key << 8);
+  key = key + (key << 3) + (key << 8);  // key *= 1 + (1 << 3) + (1 << 8)
   key = key ^ (key >> 14);
-  key = (key + (key << 2)) + (key << 4);
+  key = key + (key << 2) + (key << 4);  // key *= 1 + (1 << 2) + (1 << 4)
   key = key ^ (key >> 28);
-  key = key + (key << 31);
+  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;
 }
 
@@ -63,23 +162,56 @@ inline uint32_t twang_32from64(uint64_t key) {
  */
 
 inline uint32_t jenkins_rev_mix32(uint32_t key) {
-  key += (key << 12);
+  key += (key << 12);  // key *= (1 + (1 << 12))
   key ^= (key >> 22);
-  key += (key << 4);
+  key += (key << 4);   // key *= (1 + (1 << 4))
   key ^= (key >> 9);
-  key += (key << 10);
+  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 uint32_t FNV_32_HASH_START = 2166136261UL;
 const uint64_t FNV_64_HASH_START = 14695981039346656037ULL;
 
 inline uint32_t fnv32(const char* s,
@@ -93,11 +225,12 @@ inline uint32_t fnv32(const char* s,
 }
 
 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];
@@ -107,7 +240,7 @@ inline uint32_t fnv32_buf(const void* buf,
 }
 
 inline uint32_t fnv32(const std::string& str,
-                      uint64_t hash = FNV_32_HASH_START) {
+                      uint32_t hash = FNV_32_HASH_START) {
   return fnv32_buf(str.data(), str.size(), hash);
 }
 
@@ -122,11 +255,12 @@ inline uint64_t fnv64(const char* s,
 }
 
 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];
@@ -143,13 +277,14 @@ inline uint64_t fnv64(const std::string& str,
  * Paul Hsieh: http://www.azillionmonkeys.com/qed/hash.html
  */
 
-#define get16bits(d) (*((const uint16_t*) (d)))
+#define get16bits(d) folly::loadUnaligned<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 unsigned char* s = reinterpret_cast<const unsigned 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;
@@ -211,9 +346,21 @@ inline uint32_t hsieh_hash32_str(const std::string& str) {
 
 } // 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));
@@ -228,16 +375,87 @@ template<> struct hasher<uint32_t> {
 
 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);
+  }
+};
+
+// 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
 
-#endif
+// 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