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- // Copyright (c) 2011 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- //
- //
- // Deal with the differences between Microsoft and GNU implemenations
- // of hash_map. Allows all platforms to use |base::hash_map| and
- // |base::hash_set|.
- // eg:
- // base::hash_map<int> my_map;
- // base::hash_set<int> my_set;
- //
- // NOTE: It is an explicit non-goal of this class to provide a generic hash
- // function for pointers. If you want to hash a pointers to a particular class,
- // please define the template specialization elsewhere (for example, in its
- // header file) and keep it specific to just pointers to that class. This is
- // because identity hashes are not desirable for all types that might show up
- // in containers as pointers.
- #ifndef BASE_CONTAINERS_HASH_TABLES_H_
- #define BASE_CONTAINERS_HASH_TABLES_H_
- #include <utility>
- #include "base/basictypes.h"
- #include "base/strings/string16.h"
- #include "base/build_config.h"
- #if defined(COMPILER_MSVC)
- #include <hash_map>
- #include <hash_set>
- #define BASE_HASH_NAMESPACE stdext
- #elif defined(COMPILER_GCC)
- #if defined(OS_ANDROID)
- #define BASE_HASH_NAMESPACE std
- #else
- #define BASE_HASH_NAMESPACE __gnu_cxx
- #endif
- // This is a hack to disable the gcc 4.4 warning about hash_map and hash_set
- // being deprecated. We can get rid of this when we upgrade to VS2008 and we
- // can use <tr1/unordered_map> and <tr1/unordered_set>.
- #ifdef __DEPRECATED
- #define CHROME_OLD__DEPRECATED __DEPRECATED
- #undef __DEPRECATED
- #endif
- #if defined(OS_ANDROID)
- #include <hash_map>
- #include <hash_set>
- #else
- #include <ext/hash_map>
- #include <ext/hash_set>
- #endif
- #include <string>
- #ifdef CHROME_OLD__DEPRECATED
- #define __DEPRECATED CHROME_OLD__DEPRECATED
- #undef CHROME_OLD__DEPRECATED
- #endif
- namespace BASE_HASH_NAMESPACE {
- #if !defined(OS_ANDROID)
- // The GNU C++ library provides identity hash functions for many integral types,
- // but not for |long long|. This hash function will truncate if |size_t| is
- // narrower than |long long|. This is probably good enough for what we will
- // use it for.
- #define DEFINE_TRIVIAL_HASH(integral_type) \
- template<> \
- struct hash<integral_type> { \
- std::size_t operator()(integral_type value) const { \
- return static_cast<std::size_t>(value); \
- } \
- }
- DEFINE_TRIVIAL_HASH(long long);
- DEFINE_TRIVIAL_HASH(unsigned long long);
- #undef DEFINE_TRIVIAL_HASH
- #endif // !defined(OS_ANDROID)
- // Implement string hash functions so that strings of various flavors can
- // be used as keys in STL maps and sets. The hash algorithm comes from the
- // GNU C++ library, in <tr1/functional>. It is duplicated here because GCC
- // versions prior to 4.3.2 are unable to compile <tr1/functional> when RTTI
- // is disabled, as it is in our build.
- #define DEFINE_STRING_HASH(string_type) \
- template<> \
- struct hash<string_type> { \
- std::size_t operator()(const string_type& s) const { \
- std::size_t result = 0; \
- for (string_type::const_iterator i = s.begin(); i != s.end(); ++i) \
- result = (result * 131) + *i; \
- return result; \
- } \
- }
- DEFINE_STRING_HASH(std::string);
- DEFINE_STRING_HASH(base::string16);
- #undef DEFINE_STRING_HASH
- } // namespace BASE_HASH_NAMESPACE
- #else // COMPILER
- #error define BASE_HASH_NAMESPACE for your compiler
- #endif // COMPILER
- namespace base {
- using BASE_HASH_NAMESPACE::hash_map;
- using BASE_HASH_NAMESPACE::hash_multimap;
- using BASE_HASH_NAMESPACE::hash_multiset;
- using BASE_HASH_NAMESPACE::hash_set;
- // Implement hashing for pairs of at-most 32 bit integer values.
- // When size_t is 32 bits, we turn the 64-bit hash code into 32 bits by using
- // multiply-add hashing. This algorithm, as described in
- // Theorem 4.3.3 of the thesis "Über die Komplexität der Multiplikation in
- // eingeschränkten Branchingprogrammmodellen" by Woelfel, is:
- //
- // h32(x32, y32) = (h64(x32, y32) * rand_odd64 + rand16 * 2^16) % 2^64 / 2^32
- //
- // Contact danakj@chromium.org for any questions.
- inline std::size_t HashInts32(uint32_t value1, uint32_t value2) {
- uint64_t value1_64 = value1;
- uint64_t hash64 = (value1_64 << 32) | value2;
- if (sizeof(std::size_t) >= sizeof(uint64_t))
- return static_cast<std::size_t>(hash64);
- uint64_t odd_random = 481046412LL << 32 | 1025306955LL;
- uint32_t shift_random = 10121U << 16;
- hash64 = hash64 * odd_random + shift_random;
- std::size_t high_bits = static_cast<std::size_t>(
- hash64 >> (8 * (sizeof(uint64_t) - sizeof(std::size_t))));
- return high_bits;
- }
- // Implement hashing for pairs of up-to 64-bit integer values.
- // We use the compound integer hash method to produce a 64-bit hash code, by
- // breaking the two 64-bit inputs into 4 32-bit values:
- // http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000
- // Then we reduce our result to 32 bits if required, similar to above.
- inline std::size_t HashInts64(uint64_t value1, uint64_t value2) {
- uint32_t short_random1 = 842304669U;
- uint32_t short_random2 = 619063811U;
- uint32_t short_random3 = 937041849U;
- uint32_t short_random4 = 3309708029U;
- uint32_t value1a = static_cast<uint32_t>(value1 & 0xffffffff);
- uint32_t value1b = static_cast<uint32_t>((value1 >> 32) & 0xffffffff);
- uint32_t value2a = static_cast<uint32_t>(value2 & 0xffffffff);
- uint32_t value2b = static_cast<uint32_t>((value2 >> 32) & 0xffffffff);
- uint64_t product1 = static_cast<uint64_t>(value1a) * short_random1;
- uint64_t product2 = static_cast<uint64_t>(value1b) * short_random2;
- uint64_t product3 = static_cast<uint64_t>(value2a) * short_random3;
- uint64_t product4 = static_cast<uint64_t>(value2b) * short_random4;
- uint64_t hash64 = product1 + product2 + product3 + product4;
- if (sizeof(std::size_t) >= sizeof(uint64_t))
- return static_cast<std::size_t>(hash64);
- uint64_t odd_random = 1578233944LL << 32 | 194370989LL;
- uint32_t shift_random = 20591U << 16;
- hash64 = hash64 * odd_random + shift_random;
- std::size_t high_bits = static_cast<std::size_t>(
- hash64 >> (8 * (sizeof(uint64_t) - sizeof(std::size_t))));
- return high_bits;
- }
- #define DEFINE_32BIT_PAIR_HASH(Type1, Type2) \
- inline std::size_t HashPair(Type1 value1, Type2 value2) { \
- return HashInts32(value1, value2); \
- }
- DEFINE_32BIT_PAIR_HASH(int16_t, int16_t);
- DEFINE_32BIT_PAIR_HASH(int16_t, uint16_t);
- DEFINE_32BIT_PAIR_HASH(int16_t, int32_t);
- DEFINE_32BIT_PAIR_HASH(int16_t, uint32_t);
- DEFINE_32BIT_PAIR_HASH(uint16_t, int16_t);
- DEFINE_32BIT_PAIR_HASH(uint16_t, uint16_t);
- DEFINE_32BIT_PAIR_HASH(uint16_t, int32_t);
- DEFINE_32BIT_PAIR_HASH(uint16_t, uint32_t);
- DEFINE_32BIT_PAIR_HASH(int32_t, int16_t);
- DEFINE_32BIT_PAIR_HASH(int32_t, uint16_t);
- DEFINE_32BIT_PAIR_HASH(int32_t, int32_t);
- DEFINE_32BIT_PAIR_HASH(int32_t, uint32_t);
- DEFINE_32BIT_PAIR_HASH(uint32_t, int16_t);
- DEFINE_32BIT_PAIR_HASH(uint32_t, uint16_t);
- DEFINE_32BIT_PAIR_HASH(uint32_t, int32_t);
- DEFINE_32BIT_PAIR_HASH(uint32_t, uint32_t);
- #undef DEFINE_32BIT_PAIR_HASH
- #define DEFINE_64BIT_PAIR_HASH(Type1, Type2) \
- inline std::size_t HashPair(Type1 value1, Type2 value2) { \
- return HashInts64(value1, value2); \
- }
- DEFINE_64BIT_PAIR_HASH(int16_t, int64_t);
- DEFINE_64BIT_PAIR_HASH(int16_t, uint64_t);
- DEFINE_64BIT_PAIR_HASH(uint16_t, int64_t);
- DEFINE_64BIT_PAIR_HASH(uint16_t, uint64_t);
- DEFINE_64BIT_PAIR_HASH(int32_t, int64_t);
- DEFINE_64BIT_PAIR_HASH(int32_t, uint64_t);
- DEFINE_64BIT_PAIR_HASH(uint32_t, int64_t);
- DEFINE_64BIT_PAIR_HASH(uint32_t, uint64_t);
- DEFINE_64BIT_PAIR_HASH(int64_t, int16_t);
- DEFINE_64BIT_PAIR_HASH(int64_t, uint16_t);
- DEFINE_64BIT_PAIR_HASH(int64_t, int32_t);
- DEFINE_64BIT_PAIR_HASH(int64_t, uint32_t);
- DEFINE_64BIT_PAIR_HASH(int64_t, int64_t);
- DEFINE_64BIT_PAIR_HASH(int64_t, uint64_t);
- DEFINE_64BIT_PAIR_HASH(uint64_t, int16_t);
- DEFINE_64BIT_PAIR_HASH(uint64_t, uint16_t);
- DEFINE_64BIT_PAIR_HASH(uint64_t, int32_t);
- DEFINE_64BIT_PAIR_HASH(uint64_t, uint32_t);
- DEFINE_64BIT_PAIR_HASH(uint64_t, int64_t);
- DEFINE_64BIT_PAIR_HASH(uint64_t, uint64_t);
- #undef DEFINE_64BIT_PAIR_HASH
- } // namespace base
- namespace BASE_HASH_NAMESPACE {
- // Implement methods for hashing a pair of integers, so they can be used as
- // keys in STL containers.
- // NOTE(gejun): Specialize ptr as well which is supposed to work with
- // containers by default
- #if defined(COMPILER_MSVC)
- template<typename Type1, typename Type2>
- inline std::size_t hash_value(const std::pair<Type1, Type2>& value) {
- return base::HashPair(value.first, value.second);
- }
- template<typename Type>
- inline std::size_t hash_value(Type* ptr) {
- return (uintptr_t)ptr;
- }
- #elif defined(COMPILER_GCC)
- template<typename Type1, typename Type2>
- struct hash<std::pair<Type1, Type2> > {
- std::size_t operator()(std::pair<Type1, Type2> value) const {
- return base::HashPair(value.first, value.second);
- }
- };
- template<typename Type>
- struct hash<Type*> {
- std::size_t operator()(Type* ptr) const {
- return (uintptr_t)ptr;
- }
- };
- #else
- #error define hash<std::pair<Type1, Type2> > for your compiler
- #endif // COMPILER
- }
- #undef DEFINE_PAIR_HASH_FUNCTION_START
- #undef DEFINE_PAIR_HASH_FUNCTION_END
- #endif // BASE_CONTAINERS_HASH_TABLES_H_
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