Move hash_pair.h from cc/base into base/.

cc/base/hash_pair.h

-// Copyright (c) 2012 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.
-//
-// Defines methods for hashing a pair of integers.
-
-#ifndef CC_BASE_HASH_PAIR_H_
-#define CC_BASE_HASH_PAIR_H_
-
-#include <utility>
-
-#include "base/basictypes.h"
-#include "base/containers/hash_tables.h"
-
-#if defined(COMPILER_MSVC)
-
-#define DEFINE_PAIR_HASH_FUNCTION_START(type1, type2) \
-    template<> \
-    inline std::size_t hash_value<std::pair<type1, type2> >( \
-        const std::pair<type1, type2>& value)
-
-#define DEFINE_PAIR_HASH_FUNCTION_END()
-
-#elif defined(COMPILER_GCC)
-
-#define DEFINE_PAIR_HASH_FUNCTION_START(type1, type2) \
-    template<> \
-    struct hash<std::pair<type1, type2> > { \
-      std::size_t operator()(std::pair<type1, type2> value) const
-
-#define DEFINE_PAIR_HASH_FUNCTION_END() \
-    };
-
-#else
-#error define DEFINE_PAIR_HASH_FUNCTION_START for your compiler
-#endif  // COMPILER
-
-namespace BASE_HASH_NAMESPACE {
-
-// 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
-
-#define DEFINE_32BIT_PAIR_HASH(type1, type2) \
-    DEFINE_PAIR_HASH_FUNCTION_START(type1, type2) { \
-      uint64 first = value.first; \
-      uint32 second = value.second; \
-      uint64 hash64 = (first << 32) | second; \
-      \
-      if (sizeof(std::size_t) >= sizeof(uint64)) \
-        return static_cast<std::size_t>(hash64); \
-      \
-      uint64 odd_random = 481046412LL << 32 | 1025306954LL; \
-      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; \
-    } \
-  DEFINE_PAIR_HASH_FUNCTION_END();
-
-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
-
-// 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.
-
-#define DEFINE_64BIT_PAIR_HASH(type1, type2) \
-    DEFINE_PAIR_HASH_FUNCTION_START(type1, type2) { \
-      uint32 short_random1 = 842304669U; \
-      uint32 short_random2 = 619063811U; \
-      uint32 short_random3 = 937041849U; \
-      uint32 short_random4 = 3309708029U; \
-      \
-      uint64 value1 = value.first; \
-      uint64 value2 = value.second; \
-      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_PAIR_HASH_FUNCTION_END();
-
-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
-}
-
-#undef DEFINE_PAIR_HASH_FUNCTION_START
-#undef DEFINE_PAIR_HASH_FUNCTION_END
-
-#endif  // CC_BASE_HASH_PAIR_H_