1 // Copyright (c) 2006-2008 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_HASH_TABLES_H_ 22 #define BASE_HASH_TABLES_H_ 23 24 #include "build/build_config.h" 25 26 #include "base/string16.h" 27 28 #if defined(COMPILER_MSVC) 29 #include <hash_map> 30 #include <hash_set> 31 namespace base { 32 using stdext::hash_map; 33 using stdext::hash_set; 34 } 35 #elif defined(COMPILER_GCC) 36 // This is a hack to disable the gcc 4.4 warning about hash_map and hash_set 37 // being deprecated. We can get rid of this when we upgrade to VS2008 and we 38 // can use <tr1/unordered_map> and <tr1/unordered_set>. 39 #ifdef __DEPRECATED 40 #define CHROME_OLD__DEPRECATED __DEPRECATED 41 #undef __DEPRECATED 42 #endif 43 44 #include <ext/hash_map> 45 #include <ext/hash_set> 46 #include <string> 47 48 #ifdef CHROME_OLD__DEPRECATED 49 #define __DEPRECATED CHROME_OLD__DEPRECATED 50 #undef CHROME_OLD__DEPRECATED 51 #endif 52 53 namespace base { 54 using __gnu_cxx::hash_map; 55 using __gnu_cxx::hash_set; 56 } // namespace base 57 58 namespace __gnu_cxx { 59 60 // The GNU C++ library provides identiy hash functions for many integral types, 61 // but not for |long long|. This hash function will truncate if |size_t| is 62 // narrower than |long long|. This is probably good enough for what we will 63 // use it for. 64 65 #define DEFINE_TRIVIAL_HASH(integral_type) \ 66 template<> \ 67 struct hash<integral_type> { \ 68 std::size_t operator()(integral_type value) const { \ 69 return static_cast<std::size_t>(value); \ 70 } \ 71 } 72 73 DEFINE_TRIVIAL_HASH(long long); 74 DEFINE_TRIVIAL_HASH(unsigned long long); 75 76 #undef DEFINE_TRIVIAL_HASH 77 78 // Implement string hash functions so that strings of various flavors can 79 // be used as keys in STL maps and sets. The hash algorithm comes from the 80 // GNU C++ library, in <tr1/functional>. It is duplicated here because GCC 81 // versions prior to 4.3.2 are unable to compile <tr1/functional> when RTTI 82 // is disabled, as it is in our build. 83 84 #define DEFINE_STRING_HASH(string_type) \ 85 template<> \ 86 struct hash<string_type> { \ 87 std::size_t operator()(const string_type& s) const { \ 88 std::size_t result = 0; \ 89 for (string_type::const_iterator i = s.begin(); i != s.end(); ++i) \ 90 result = (result * 131) + *i; \ 91 return result; \ 92 } \ 93 } 94 95 DEFINE_STRING_HASH(std::string); 96 DEFINE_STRING_HASH(std::wstring); 97 98 #if defined(WCHAR_T_IS_UTF32) 99 // If string16 and std::wstring are not the same type, provide a 100 // specialization for string16. 101 DEFINE_STRING_HASH(string16); 102 #endif // WCHAR_T_IS_UTF32 103 104 #undef DEFINE_STRING_HASH 105 106 } // namespace __gnu_cxx 107 108 #endif // COMPILER 109 110 #endif // BASE_HASH_TABLES_H_ 111
