diff options
Diffstat (limited to 'src/util/numeric.cpp')
| -rw-r--r-- | src/util/numeric.cpp | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/src/util/numeric.cpp b/src/util/numeric.cpp index 67df4ffba..0426656a5 100644 --- a/src/util/numeric.cpp +++ b/src/util/numeric.cpp @@ -22,6 +22,7 @@ with this program; if not, write to the Free Software Foundation, Inc., #include "../log.h" #include "../constants.h" // BS, MAP_BLOCKSIZE +#include <string.h> #include <iostream> // Calculate the borders of a "d-radius" cube @@ -139,6 +140,49 @@ int myrand_range(int min, int max) return (myrand()%(max-min+1))+min; } +// 64-bit unaligned version of MurmurHash +u64 murmur_hash_64_ua(const void *key, int len, unsigned int seed) +{ + const u64 m = 0xc6a4a7935bd1e995; + const int r = 47; + u64 h = seed ^ (len * m); + + const u64 *data = (const u64 *)key; + const u64 *end = data + (len / 8); + + while (data != end) { + u64 k; + memcpy(&k, data, sizeof(u64)); + data++; + + k *= m; + k ^= k >> r; + k *= m; + + h ^= k; + h *= m; + } + + const unsigned char *data2 = (const unsigned char *)data; + switch (len & 7) { + case 7: h ^= (u64)data2[6] << 48; + case 6: h ^= (u64)data2[5] << 40; + case 5: h ^= (u64)data2[4] << 32; + case 4: h ^= (u64)data2[3] << 24; + case 3: h ^= (u64)data2[2] << 16; + case 2: h ^= (u64)data2[1] << 8; + case 1: h ^= (u64)data2[0]; + h *= m; + } + + h ^= h >> r; + h *= m; + h ^= h >> r; + + return h; +} + + /* blockpos: position of block in block coordinates camera_pos: position of camera in nodes |