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 66 namespace 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 82 DEFINE_TRIVIAL_HASH(long long); 83 DEFINE_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 } 104 105 DEFINE_STRING_HASH(std::string); 106 DEFINE_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 115 116 namespace base { 117 using BASE_HASH_NAMESPACE::hash_map; 118 using BASE_HASH_NAMESPACE::hash_multimap; 119 using BASE_HASH_NAMESPACE::hash_multiset; 120 using 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 "ber die Komplexitt der Multiplikation in 126 // eingeschrnkten 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 (at) chromium.org for any questions. 131 inline 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. 152 inline 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) \ 183 inline std::size_t HashPair(Type1 value1, Type2 value2) { \ 184 return HashInts32(value1, value2); \ 185 } 186 187 DEFINE_32BIT_PAIR_HASH(int16, int16); 188 DEFINE_32BIT_PAIR_HASH(int16, uint16); 189 DEFINE_32BIT_PAIR_HASH(int16, int32); 190 DEFINE_32BIT_PAIR_HASH(int16, uint32); 191 DEFINE_32BIT_PAIR_HASH(uint16, int16); 192 DEFINE_32BIT_PAIR_HASH(uint16, uint16); 193 DEFINE_32BIT_PAIR_HASH(uint16, int32); 194 DEFINE_32BIT_PAIR_HASH(uint16, uint32); 195 DEFINE_32BIT_PAIR_HASH(int32, int16); 196 DEFINE_32BIT_PAIR_HASH(int32, uint16); 197 DEFINE_32BIT_PAIR_HASH(int32, int32); 198 DEFINE_32BIT_PAIR_HASH(int32, uint32); 199 DEFINE_32BIT_PAIR_HASH(uint32, int16); 200 DEFINE_32BIT_PAIR_HASH(uint32, uint16); 201 DEFINE_32BIT_PAIR_HASH(uint32, int32); 202 DEFINE_32BIT_PAIR_HASH(uint32, uint32); 203 204 #undef DEFINE_32BIT_PAIR_HASH 205 206 #define DEFINE_64BIT_PAIR_HASH(Type1, Type2) \ 207 inline std::size_t HashPair(Type1 value1, Type2 value2) { \ 208 return HashInts64(value1, value2); \ 209 } 210 211 DEFINE_64BIT_PAIR_HASH(int16, int64); 212 DEFINE_64BIT_PAIR_HASH(int16, uint64); 213 DEFINE_64BIT_PAIR_HASH(uint16, int64); 214 DEFINE_64BIT_PAIR_HASH(uint16, uint64); 215 DEFINE_64BIT_PAIR_HASH(int32, int64); 216 DEFINE_64BIT_PAIR_HASH(int32, uint64); 217 DEFINE_64BIT_PAIR_HASH(uint32, int64); 218 DEFINE_64BIT_PAIR_HASH(uint32, uint64); 219 DEFINE_64BIT_PAIR_HASH(int64, int16); 220 DEFINE_64BIT_PAIR_HASH(int64, uint16); 221 DEFINE_64BIT_PAIR_HASH(int64, int32); 222 DEFINE_64BIT_PAIR_HASH(int64, uint32); 223 DEFINE_64BIT_PAIR_HASH(int64, int64); 224 DEFINE_64BIT_PAIR_HASH(int64, uint64); 225 DEFINE_64BIT_PAIR_HASH(uint64, int16); 226 DEFINE_64BIT_PAIR_HASH(uint64, uint16); 227 DEFINE_64BIT_PAIR_HASH(uint64, int32); 228 DEFINE_64BIT_PAIR_HASH(uint64, uint32); 229 DEFINE_64BIT_PAIR_HASH(uint64, int64); 230 DEFINE_64BIT_PAIR_HASH(uint64, uint64); 231 232 #undef DEFINE_64BIT_PAIR_HASH 233 } // namespace base 234 235 namespace 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) 241 242 template<typename Type1, typename Type2> 243 inline 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) 248 template<typename Type1, typename Type2> 249 struct 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
