265 lines
8.5 KiB
C++
265 lines
8.5 KiB
C++
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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//
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//
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// Deal with the differences between Microsoft and GNU implemenations
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// of hash_map. Allows all platforms to use |base::hash_map| and
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// |base::hash_set|.
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// eg:
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// base::hash_map<int> my_map;
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// base::hash_set<int> my_set;
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//
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// NOTE: It is an explicit non-goal of this class to provide a generic hash
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// function for pointers. If you want to hash a pointers to a particular class,
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// please define the template specialization elsewhere (for example, in its
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// header file) and keep it specific to just pointers to that class. This is
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// because identity hashes are not desirable for all types that might show up
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// in containers as pointers.
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#ifndef BASE_CONTAINERS_HASH_TABLES_H_
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#define BASE_CONTAINERS_HASH_TABLES_H_
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#include <utility>
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#include "base/basictypes.h"
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#include "base/strings/string16.h"
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#include "build/build_config.h"
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#if defined(COMPILER_MSVC)
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#include <hash_map>
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#include <hash_set>
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#define BASE_HASH_NAMESPACE stdext
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#elif defined(COMPILER_GCC)
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#if defined(OS_ANDROID)
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#define BASE_HASH_NAMESPACE std
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#else
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#define BASE_HASH_NAMESPACE __gnu_cxx
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#endif
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// This is a hack to disable the gcc 4.4 warning about hash_map and hash_set
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// being deprecated. We can get rid of this when we upgrade to VS2008 and we
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// can use <tr1/unordered_map> and <tr1/unordered_set>.
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#ifdef __DEPRECATED
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#define CHROME_OLD__DEPRECATED __DEPRECATED
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#undef __DEPRECATED
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#endif
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#if defined(OS_ANDROID)
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#include <hash_map>
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#include <hash_set>
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#else
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#include <ext/hash_map>
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#include <ext/hash_set>
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#endif
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#include <string>
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#ifdef CHROME_OLD__DEPRECATED
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#define __DEPRECATED CHROME_OLD__DEPRECATED
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#undef CHROME_OLD__DEPRECATED
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#endif
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namespace BASE_HASH_NAMESPACE {
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#if !defined(OS_ANDROID)
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// The GNU C++ library provides identity hash functions for many integral types,
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// but not for |long long|. This hash function will truncate if |size_t| is
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// narrower than |long long|. This is probably good enough for what we will
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// use it for.
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#define DEFINE_TRIVIAL_HASH(integral_type) \
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template<> \
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struct hash<integral_type> { \
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std::size_t operator()(integral_type value) const { \
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return static_cast<std::size_t>(value); \
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} \
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}
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DEFINE_TRIVIAL_HASH(long long);
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DEFINE_TRIVIAL_HASH(unsigned long long);
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#undef DEFINE_TRIVIAL_HASH
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#endif // !defined(OS_ANDROID)
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// Implement string hash functions so that strings of various flavors can
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// be used as keys in STL maps and sets. The hash algorithm comes from the
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// GNU C++ library, in <tr1/functional>. It is duplicated here because GCC
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// versions prior to 4.3.2 are unable to compile <tr1/functional> when RTTI
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// is disabled, as it is in our build.
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#define DEFINE_STRING_HASH(string_type) \
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template<> \
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struct hash<string_type> { \
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std::size_t operator()(const string_type& s) const { \
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std::size_t result = 0; \
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for (string_type::const_iterator i = s.begin(); i != s.end(); ++i) \
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result = (result * 131) + *i; \
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return result; \
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} \
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}
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DEFINE_STRING_HASH(std::string);
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DEFINE_STRING_HASH(string16);
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#undef DEFINE_STRING_HASH
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} // namespace BASE_HASH_NAMESPACE
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#else // COMPILER
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#error define BASE_HASH_NAMESPACE for your compiler
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#endif // COMPILER
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namespace base {
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using BASE_HASH_NAMESPACE::hash_map;
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using BASE_HASH_NAMESPACE::hash_multimap;
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using BASE_HASH_NAMESPACE::hash_multiset;
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using BASE_HASH_NAMESPACE::hash_set;
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// Implement hashing for pairs of at-most 32 bit integer values.
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// When size_t is 32 bits, we turn the 64-bit hash code into 32 bits by using
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// multiply-add hashing. This algorithm, as described in
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// Theorem 4.3.3 of the thesis "Über die Komplexität der Multiplikation in
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// eingeschränkten Branchingprogrammmodellen" by Woelfel, is:
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//
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// h32(x32, y32) = (h64(x32, y32) * rand_odd64 + rand16 * 2^16) % 2^64 / 2^32
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//
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// Contact danakj@chromium.org for any questions.
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inline std::size_t HashInts32(uint32 value1, uint32 value2) {
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uint64 value1_64 = value1;
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uint64 hash64 = (value1_64 << 32) | value2;
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if (sizeof(std::size_t) >= sizeof(uint64))
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return static_cast<std::size_t>(hash64);
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uint64 odd_random = 481046412LL << 32 | 1025306955LL;
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uint32 shift_random = 10121U << 16;
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hash64 = hash64 * odd_random + shift_random;
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std::size_t high_bits = static_cast<std::size_t>(
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hash64 >> (sizeof(uint64) - sizeof(std::size_t)));
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return high_bits;
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}
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// Implement hashing for pairs of up-to 64-bit integer values.
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// We use the compound integer hash method to produce a 64-bit hash code, by
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// breaking the two 64-bit inputs into 4 32-bit values:
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// http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000
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// Then we reduce our result to 32 bits if required, similar to above.
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inline std::size_t HashInts64(uint64 value1, uint64 value2) {
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uint32 short_random1 = 842304669U;
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uint32 short_random2 = 619063811U;
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uint32 short_random3 = 937041849U;
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uint32 short_random4 = 3309708029U;
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uint32 value1a = static_cast<uint32>(value1 & 0xffffffff);
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uint32 value1b = static_cast<uint32>((value1 >> 32) & 0xffffffff);
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uint32 value2a = static_cast<uint32>(value2 & 0xffffffff);
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uint32 value2b = static_cast<uint32>((value2 >> 32) & 0xffffffff);
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uint64 product1 = static_cast<uint64>(value1a) * short_random1;
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uint64 product2 = static_cast<uint64>(value1b) * short_random2;
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uint64 product3 = static_cast<uint64>(value2a) * short_random3;
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uint64 product4 = static_cast<uint64>(value2b) * short_random4;
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uint64 hash64 = product1 + product2 + product3 + product4;
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if (sizeof(std::size_t) >= sizeof(uint64))
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return static_cast<std::size_t>(hash64);
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uint64 odd_random = 1578233944LL << 32 | 194370989LL;
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uint32 shift_random = 20591U << 16;
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hash64 = hash64 * odd_random + shift_random;
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std::size_t high_bits = static_cast<std::size_t>(
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hash64 >> (sizeof(uint64) - sizeof(std::size_t)));
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return high_bits;
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}
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#define DEFINE_32BIT_PAIR_HASH(Type1, Type2) \
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inline std::size_t HashPair(Type1 value1, Type2 value2) { \
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return HashInts32(value1, value2); \
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}
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DEFINE_32BIT_PAIR_HASH(int16, int16);
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DEFINE_32BIT_PAIR_HASH(int16, uint16);
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DEFINE_32BIT_PAIR_HASH(int16, int32);
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DEFINE_32BIT_PAIR_HASH(int16, uint32);
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DEFINE_32BIT_PAIR_HASH(uint16, int16);
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DEFINE_32BIT_PAIR_HASH(uint16, uint16);
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DEFINE_32BIT_PAIR_HASH(uint16, int32);
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DEFINE_32BIT_PAIR_HASH(uint16, uint32);
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DEFINE_32BIT_PAIR_HASH(int32, int16);
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DEFINE_32BIT_PAIR_HASH(int32, uint16);
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DEFINE_32BIT_PAIR_HASH(int32, int32);
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DEFINE_32BIT_PAIR_HASH(int32, uint32);
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DEFINE_32BIT_PAIR_HASH(uint32, int16);
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DEFINE_32BIT_PAIR_HASH(uint32, uint16);
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DEFINE_32BIT_PAIR_HASH(uint32, int32);
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DEFINE_32BIT_PAIR_HASH(uint32, uint32);
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#undef DEFINE_32BIT_PAIR_HASH
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#define DEFINE_64BIT_PAIR_HASH(Type1, Type2) \
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inline std::size_t HashPair(Type1 value1, Type2 value2) { \
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return HashInts64(value1, value2); \
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}
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DEFINE_64BIT_PAIR_HASH(int16, int64);
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DEFINE_64BIT_PAIR_HASH(int16, uint64);
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DEFINE_64BIT_PAIR_HASH(uint16, int64);
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DEFINE_64BIT_PAIR_HASH(uint16, uint64);
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DEFINE_64BIT_PAIR_HASH(int32, int64);
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DEFINE_64BIT_PAIR_HASH(int32, uint64);
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DEFINE_64BIT_PAIR_HASH(uint32, int64);
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DEFINE_64BIT_PAIR_HASH(uint32, uint64);
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DEFINE_64BIT_PAIR_HASH(int64, int16);
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DEFINE_64BIT_PAIR_HASH(int64, uint16);
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DEFINE_64BIT_PAIR_HASH(int64, int32);
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DEFINE_64BIT_PAIR_HASH(int64, uint32);
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DEFINE_64BIT_PAIR_HASH(int64, int64);
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DEFINE_64BIT_PAIR_HASH(int64, uint64);
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DEFINE_64BIT_PAIR_HASH(uint64, int16);
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DEFINE_64BIT_PAIR_HASH(uint64, uint16);
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DEFINE_64BIT_PAIR_HASH(uint64, int32);
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DEFINE_64BIT_PAIR_HASH(uint64, uint32);
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DEFINE_64BIT_PAIR_HASH(uint64, int64);
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DEFINE_64BIT_PAIR_HASH(uint64, uint64);
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#undef DEFINE_64BIT_PAIR_HASH
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} // namespace base
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namespace BASE_HASH_NAMESPACE {
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// Implement methods for hashing a pair of integers, so they can be used as
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// keys in STL containers.
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#if defined(COMPILER_MSVC)
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template<typename Type1, typename Type2>
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inline std::size_t hash_value(const std::pair<Type1, Type2>& value) {
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return base::HashPair(value.first, value.second);
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}
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#elif defined(COMPILER_GCC)
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template<typename Type1, typename Type2>
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struct hash<std::pair<Type1, Type2> > {
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std::size_t operator()(std::pair<Type1, Type2> value) const {
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return base::HashPair(value.first, value.second);
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}
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};
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#else
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#error define hash<std::pair<Type1, Type2> > for your compiler
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#endif // COMPILER
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}
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#undef DEFINE_PAIR_HASH_FUNCTION_START
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#undef DEFINE_PAIR_HASH_FUNCTION_END
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#endif // BASE_CONTAINERS_HASH_TABLES_H_
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