// Copyright (c) 2011 The LevelDB Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. See the AUTHORS file for names of contributors. #include <string.h> #include "util/coding.h" #include "util/hash.h" namespace leveldb { uint32_t Hash(const char* data, size_t n, uint32_t seed) { // Similar to murmur hash const uint32_t m = 0xc6a4a793; const uint32_t r = 24; const char* limit = data + n; uint32_t h = seed ^ (n * m); // Pick up four bytes at a time while (data + 4 <= limit) { uint32_t w = DecodeFixed32(data); data += 4; h += w; h *= m; h ^= (h >> 16); } // Pick up remaining bytes switch (limit - data) { case 3: h += data[2] << 16; // fall through case 2: h += data[1] << 8; // fall through case 1: h += data[0]; h *= m; h ^= (h >> r); break; } return h; } }