| // Copyright 2010 Google Inc. All Rights Reserved. |
| // Authors: jyrki@google.com (Jyrki Alakuijala), gpike@google.com (Geoff Pike) |
| |
| #ifndef UTIL_HASH_HASH128TO64_H_ |
| #define UTIL_HASH_HASH128TO64_H_ |
| |
| #include "gutil/int128.h" |
| #include "gutil/integral_types.h" |
| |
| // Hash 128 input bits down to 64 bits of output. |
| // This is intended to be a reasonably good hash function. |
| // It may change from time to time. |
| inline uint64 Hash128to64(const uint128& x) { |
| // Murmur-inspired hashing. |
| const uint64 kMul = 0xc6a4a7935bd1e995ULL; |
| uint64 a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul; |
| a ^= (a >> 47); |
| uint64 b = (Uint128High64(x) ^ a) * kMul; |
| b ^= (b >> 47); |
| b *= kMul; |
| return b; |
| } |
| |
| #endif // UTIL_HASH_HASH128TO64_H_ |
