Index: base/containers/hash_tables.h |
diff --git a/base/containers/hash_tables.h b/base/containers/hash_tables.h |
index 13d413b65ed659444206a34d0a996676aefc5c8d..0615e0dd33775758d674f4c392dd059043f117fd 100644 |
--- a/base/containers/hash_tables.h |
+++ b/base/containers/hash_tables.h |
@@ -21,6 +21,9 @@ |
#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" |
@@ -117,4 +120,146 @@ using BASE_HASH_NAMESPACE::hash_multiset; |
using BASE_HASH_NAMESPACE::hash_set; |
} |
+ |
+// Implement methods for hashing a pair of integers, so they can be used as |
+// keys in STL containers. |
+ |
+#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 |
+// |
+// Contact danakj@chromium.org for any questions. |
+#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 // BASE_CONTAINERS_HASH_TABLES_H_ |