hash_tables.h revision a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7
1// Copyright (c) 2011 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4// 5 6// 7// Deal with the differences between Microsoft and GNU implemenations 8// of hash_map. Allows all platforms to use |base::hash_map| and 9// |base::hash_set|. 10// eg: 11// base::hash_map<int> my_map; 12// base::hash_set<int> my_set; 13// 14// NOTE: It is an explicit non-goal of this class to provide a generic hash 15// function for pointers. If you want to hash a pointers to a particular class, 16// please define the template specialization elsewhere (for example, in its 17// header file) and keep it specific to just pointers to that class. This is 18// because identity hashes are not desirable for all types that might show up 19// in containers as pointers. 20 21#ifndef BASE_CONTAINERS_HASH_TABLES_H_ 22#define BASE_CONTAINERS_HASH_TABLES_H_ 23 24#include <utility> 25 26#include "base/basictypes.h" 27#include "base/strings/string16.h" 28#include "build/build_config.h" 29 30#if defined(COMPILER_MSVC) 31#include <hash_map> 32#include <hash_set> 33 34#define BASE_HASH_NAMESPACE stdext 35 36#elif defined(COMPILER_GCC) 37#if defined(OS_ANDROID) 38#define BASE_HASH_NAMESPACE std 39#else 40#define BASE_HASH_NAMESPACE __gnu_cxx 41#endif 42 43// This is a hack to disable the gcc 4.4 warning about hash_map and hash_set 44// being deprecated. We can get rid of this when we upgrade to VS2008 and we 45// can use <tr1/unordered_map> and <tr1/unordered_set>. 46#ifdef __DEPRECATED 47#define CHROME_OLD__DEPRECATED __DEPRECATED 48#undef __DEPRECATED 49#endif 50 51#if defined(OS_ANDROID) 52#include <hash_map> 53#include <hash_set> 54#else 55#include <ext/hash_map> 56#include <ext/hash_set> 57#endif 58 59#include <string> 60 61#ifdef CHROME_OLD__DEPRECATED 62#define __DEPRECATED CHROME_OLD__DEPRECATED 63#undef CHROME_OLD__DEPRECATED 64#endif 65 66namespace BASE_HASH_NAMESPACE { 67 68#if !defined(OS_ANDROID) 69// The GNU C++ library provides identity hash functions for many integral types, 70// but not for |long long|. This hash function will truncate if |size_t| is 71// narrower than |long long|. This is probably good enough for what we will 72// use it for. 73 74#define DEFINE_TRIVIAL_HASH(integral_type) \ 75 template<> \ 76 struct hash<integral_type> { \ 77 std::size_t operator()(integral_type value) const { \ 78 return static_cast<std::size_t>(value); \ 79 } \ 80 } 81 82DEFINE_TRIVIAL_HASH(long long); 83DEFINE_TRIVIAL_HASH(unsigned long long); 84 85#undef DEFINE_TRIVIAL_HASH 86#endif // !defined(OS_ANDROID) 87 88// Implement string hash functions so that strings of various flavors can 89// be used as keys in STL maps and sets. The hash algorithm comes from the 90// GNU C++ library, in <tr1/functional>. It is duplicated here because GCC 91// versions prior to 4.3.2 are unable to compile <tr1/functional> when RTTI 92// is disabled, as it is in our build. 93 94#define DEFINE_STRING_HASH(string_type) \ 95 template<> \ 96 struct hash<string_type> { \ 97 std::size_t operator()(const string_type& s) const { \ 98 std::size_t result = 0; \ 99 for (string_type::const_iterator i = s.begin(); i != s.end(); ++i) \ 100 result = (result * 131) + *i; \ 101 return result; \ 102 } \ 103 } 104 105DEFINE_STRING_HASH(std::string); 106DEFINE_STRING_HASH(base::string16); 107 108#undef DEFINE_STRING_HASH 109 110} // namespace BASE_HASH_NAMESPACE 111 112#else // COMPILER 113#error define BASE_HASH_NAMESPACE for your compiler 114#endif // COMPILER 115 116namespace base { 117using BASE_HASH_NAMESPACE::hash_map; 118using BASE_HASH_NAMESPACE::hash_multimap; 119using BASE_HASH_NAMESPACE::hash_multiset; 120using BASE_HASH_NAMESPACE::hash_set; 121 122// Implement hashing for pairs of at-most 32 bit integer values. 123// When size_t is 32 bits, we turn the 64-bit hash code into 32 bits by using 124// multiply-add hashing. This algorithm, as described in 125// Theorem 4.3.3 of the thesis "Über die Komplexität der Multiplikation in 126// eingeschränkten Branchingprogrammmodellen" by Woelfel, is: 127// 128// h32(x32, y32) = (h64(x32, y32) * rand_odd64 + rand16 * 2^16) % 2^64 / 2^32 129// 130// Contact danakj@chromium.org for any questions. 131inline std::size_t HashInts32(uint32 value1, uint32 value2) { 132 uint64 value1_64 = value1; 133 uint64 hash64 = (value1_64 << 32) | value2; 134 135 if (sizeof(std::size_t) >= sizeof(uint64)) 136 return static_cast<std::size_t>(hash64); 137 138 uint64 odd_random = 481046412LL << 32 | 1025306955LL; 139 uint32 shift_random = 10121U << 16; 140 141 hash64 = hash64 * odd_random + shift_random; 142 std::size_t high_bits = static_cast<std::size_t>( 143 hash64 >> (sizeof(uint64) - sizeof(std::size_t))); 144 return high_bits; 145} 146 147// Implement hashing for pairs of up-to 64-bit integer values. 148// We use the compound integer hash method to produce a 64-bit hash code, by 149// breaking the two 64-bit inputs into 4 32-bit values: 150// http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000 151// Then we reduce our result to 32 bits if required, similar to above. 152inline std::size_t HashInts64(uint64 value1, uint64 value2) { 153 uint32 short_random1 = 842304669U; 154 uint32 short_random2 = 619063811U; 155 uint32 short_random3 = 937041849U; 156 uint32 short_random4 = 3309708029U; 157 158 uint32 value1a = static_cast<uint32>(value1 & 0xffffffff); 159 uint32 value1b = static_cast<uint32>((value1 >> 32) & 0xffffffff); 160 uint32 value2a = static_cast<uint32>(value2 & 0xffffffff); 161 uint32 value2b = static_cast<uint32>((value2 >> 32) & 0xffffffff); 162 163 uint64 product1 = static_cast<uint64>(value1a) * short_random1; 164 uint64 product2 = static_cast<uint64>(value1b) * short_random2; 165 uint64 product3 = static_cast<uint64>(value2a) * short_random3; 166 uint64 product4 = static_cast<uint64>(value2b) * short_random4; 167 168 uint64 hash64 = product1 + product2 + product3 + product4; 169 170 if (sizeof(std::size_t) >= sizeof(uint64)) 171 return static_cast<std::size_t>(hash64); 172 173 uint64 odd_random = 1578233944LL << 32 | 194370989LL; 174 uint32 shift_random = 20591U << 16; 175 176 hash64 = hash64 * odd_random + shift_random; 177 std::size_t high_bits = static_cast<std::size_t>( 178 hash64 >> (sizeof(uint64) - sizeof(std::size_t))); 179 return high_bits; 180} 181 182#define DEFINE_32BIT_PAIR_HASH(Type1, Type2) \ 183inline std::size_t HashPair(Type1 value1, Type2 value2) { \ 184 return HashInts32(value1, value2); \ 185} 186 187DEFINE_32BIT_PAIR_HASH(int16, int16); 188DEFINE_32BIT_PAIR_HASH(int16, uint16); 189DEFINE_32BIT_PAIR_HASH(int16, int32); 190DEFINE_32BIT_PAIR_HASH(int16, uint32); 191DEFINE_32BIT_PAIR_HASH(uint16, int16); 192DEFINE_32BIT_PAIR_HASH(uint16, uint16); 193DEFINE_32BIT_PAIR_HASH(uint16, int32); 194DEFINE_32BIT_PAIR_HASH(uint16, uint32); 195DEFINE_32BIT_PAIR_HASH(int32, int16); 196DEFINE_32BIT_PAIR_HASH(int32, uint16); 197DEFINE_32BIT_PAIR_HASH(int32, int32); 198DEFINE_32BIT_PAIR_HASH(int32, uint32); 199DEFINE_32BIT_PAIR_HASH(uint32, int16); 200DEFINE_32BIT_PAIR_HASH(uint32, uint16); 201DEFINE_32BIT_PAIR_HASH(uint32, int32); 202DEFINE_32BIT_PAIR_HASH(uint32, uint32); 203 204#undef DEFINE_32BIT_PAIR_HASH 205 206#define DEFINE_64BIT_PAIR_HASH(Type1, Type2) \ 207inline std::size_t HashPair(Type1 value1, Type2 value2) { \ 208 return HashInts64(value1, value2); \ 209} 210 211DEFINE_64BIT_PAIR_HASH(int16, int64); 212DEFINE_64BIT_PAIR_HASH(int16, uint64); 213DEFINE_64BIT_PAIR_HASH(uint16, int64); 214DEFINE_64BIT_PAIR_HASH(uint16, uint64); 215DEFINE_64BIT_PAIR_HASH(int32, int64); 216DEFINE_64BIT_PAIR_HASH(int32, uint64); 217DEFINE_64BIT_PAIR_HASH(uint32, int64); 218DEFINE_64BIT_PAIR_HASH(uint32, uint64); 219DEFINE_64BIT_PAIR_HASH(int64, int16); 220DEFINE_64BIT_PAIR_HASH(int64, uint16); 221DEFINE_64BIT_PAIR_HASH(int64, int32); 222DEFINE_64BIT_PAIR_HASH(int64, uint32); 223DEFINE_64BIT_PAIR_HASH(int64, int64); 224DEFINE_64BIT_PAIR_HASH(int64, uint64); 225DEFINE_64BIT_PAIR_HASH(uint64, int16); 226DEFINE_64BIT_PAIR_HASH(uint64, uint16); 227DEFINE_64BIT_PAIR_HASH(uint64, int32); 228DEFINE_64BIT_PAIR_HASH(uint64, uint32); 229DEFINE_64BIT_PAIR_HASH(uint64, int64); 230DEFINE_64BIT_PAIR_HASH(uint64, uint64); 231 232#undef DEFINE_64BIT_PAIR_HASH 233} // namespace base 234 235namespace BASE_HASH_NAMESPACE { 236 237// Implement methods for hashing a pair of integers, so they can be used as 238// keys in STL containers. 239 240#if defined(COMPILER_MSVC) 241 242template<typename Type1, typename Type2> 243inline std::size_t hash_value(const std::pair<Type1, Type2>& value) { 244 return base::HashPair(value.first, value.second); 245} 246 247#elif defined(COMPILER_GCC) 248template<typename Type1, typename Type2> 249struct hash<std::pair<Type1, Type2> > { 250 std::size_t operator()(std::pair<Type1, Type2> value) const { 251 return base::HashPair(value.first, value.second); 252 } 253}; 254 255#else 256#error define hash<std::pair<Type1, Type2> > for your compiler 257#endif // COMPILER 258 259} 260 261#undef DEFINE_PAIR_HASH_FUNCTION_START 262#undef DEFINE_PAIR_HASH_FUNCTION_END 263 264#endif // BASE_CONTAINERS_HASH_TABLES_H_ 265