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author | Zeno Albisser <zeno.albisser@digia.com> | 2013-08-15 21:46:11 +0200 |
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committer | Zeno Albisser <zeno.albisser@digia.com> | 2013-08-15 21:46:11 +0200 |
commit | 679147eead574d186ebf3069647b4c23e8ccace6 (patch) | |
tree | fc247a0ac8ff119f7c8550879ebb6d3dd8d1ff69 /chromium/base/containers/hash_tables.h | |
download | qtwebengine-chromium-679147eead574d186ebf3069647b4c23e8ccace6.tar.gz |
Initial import.
Diffstat (limited to 'chromium/base/containers/hash_tables.h')
-rw-r--r-- | chromium/base/containers/hash_tables.h | 264 |
1 files changed, 264 insertions, 0 deletions
diff --git a/chromium/base/containers/hash_tables.h b/chromium/base/containers/hash_tables.h new file mode 100644 index 00000000000..2a2b52f9da6 --- /dev/null +++ b/chromium/base/containers/hash_tables.h @@ -0,0 +1,264 @@ +// 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 "build/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(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 value1, uint32 value2) { + uint64 value1_64 = value1; + uint64 hash64 = (value1_64 << 32) | value2; + + if (sizeof(std::size_t) >= sizeof(uint64)) + return static_cast<std::size_t>(hash64); + + uint64 odd_random = 481046412LL << 32 | 1025306955LL; + uint32 shift_random = 10121U << 16; + + hash64 = hash64 * odd_random + shift_random; + std::size_t high_bits = static_cast<std::size_t>( + hash64 >> (sizeof(uint64) - 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 value1, uint64 value2) { + uint32 short_random1 = 842304669U; + uint32 short_random2 = 619063811U; + uint32 short_random3 = 937041849U; + uint32 short_random4 = 3309708029U; + + uint32 value1a = static_cast<uint32>(value1 & 0xffffffff); + uint32 value1b = static_cast<uint32>((value1 >> 32) & 0xffffffff); + uint32 value2a = static_cast<uint32>(value2 & 0xffffffff); + uint32 value2b = static_cast<uint32>((value2 >> 32) & 0xffffffff); + + uint64 product1 = static_cast<uint64>(value1a) * short_random1; + uint64 product2 = static_cast<uint64>(value1b) * short_random2; + uint64 product3 = static_cast<uint64>(value2a) * short_random3; + uint64 product4 = static_cast<uint64>(value2b) * short_random4; + + uint64 hash64 = product1 + product2 + product3 + product4; + + if (sizeof(std::size_t) >= sizeof(uint64)) + return static_cast<std::size_t>(hash64); + + uint64 odd_random = 1578233944LL << 32 | 194370989LL; + uint32 shift_random = 20591U << 16; + + hash64 = hash64 * odd_random + shift_random; + std::size_t high_bits = static_cast<std::size_t>( + hash64 >> (sizeof(uint64) - 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, int16); +DEFINE_32BIT_PAIR_HASH(int16, uint16); +DEFINE_32BIT_PAIR_HASH(int16, int32); +DEFINE_32BIT_PAIR_HASH(int16, uint32); +DEFINE_32BIT_PAIR_HASH(uint16, int16); +DEFINE_32BIT_PAIR_HASH(uint16, uint16); +DEFINE_32BIT_PAIR_HASH(uint16, int32); +DEFINE_32BIT_PAIR_HASH(uint16, uint32); +DEFINE_32BIT_PAIR_HASH(int32, int16); +DEFINE_32BIT_PAIR_HASH(int32, uint16); +DEFINE_32BIT_PAIR_HASH(int32, int32); +DEFINE_32BIT_PAIR_HASH(int32, uint32); +DEFINE_32BIT_PAIR_HASH(uint32, int16); +DEFINE_32BIT_PAIR_HASH(uint32, uint16); +DEFINE_32BIT_PAIR_HASH(uint32, int32); +DEFINE_32BIT_PAIR_HASH(uint32, uint32); + +#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, int64); +DEFINE_64BIT_PAIR_HASH(int16, uint64); +DEFINE_64BIT_PAIR_HASH(uint16, int64); +DEFINE_64BIT_PAIR_HASH(uint16, uint64); +DEFINE_64BIT_PAIR_HASH(int32, int64); +DEFINE_64BIT_PAIR_HASH(int32, uint64); +DEFINE_64BIT_PAIR_HASH(uint32, int64); +DEFINE_64BIT_PAIR_HASH(uint32, uint64); +DEFINE_64BIT_PAIR_HASH(int64, int16); +DEFINE_64BIT_PAIR_HASH(int64, uint16); +DEFINE_64BIT_PAIR_HASH(int64, int32); +DEFINE_64BIT_PAIR_HASH(int64, uint32); +DEFINE_64BIT_PAIR_HASH(int64, int64); +DEFINE_64BIT_PAIR_HASH(int64, uint64); +DEFINE_64BIT_PAIR_HASH(uint64, int16); +DEFINE_64BIT_PAIR_HASH(uint64, uint16); +DEFINE_64BIT_PAIR_HASH(uint64, int32); +DEFINE_64BIT_PAIR_HASH(uint64, uint32); +DEFINE_64BIT_PAIR_HASH(uint64, int64); +DEFINE_64BIT_PAIR_HASH(uint64, uint64); + +#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. + +#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); +} + +#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); + } +}; + +#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_ |