// Copyright (c) 2018 Kenton Varda and contributors // Licensed under the MIT License: // // Permission is hereby granted, free of charge, to any person obtaining a copy // of this software and associated documentation files (the "Software"), to deal // in the Software without restriction, including without limitation the rights // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell // copies of the Software, and to permit persons to whom the Software is // furnished to do so, subject to the following conditions: // // The above copyright notice and this permission notice shall be included in // all copies or substantial portions of the Software. // // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN // THE SOFTWARE. #include "hash.h" namespace kj { namespace _ { // private uint HashCoder::operator*(ArrayPtr<const byte> s) const { // murmur2 adapted from libc++ source code. // // TODO(perf): Use CityHash or FarmHash on 64-bit machines? They seem optimized for x86-64; what // about ARM? Ask Vlad for advice. constexpr uint m = 0x5bd1e995; constexpr uint r = 24; uint h = s.size(); const byte* data = s.begin(); uint len = s.size(); for (; len >= 4; data += 4, len -= 4) { uint k; memcpy(&k, data, sizeof(k)); k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; } switch (len) { case 3: h ^= data[2] << 16; case 2: h ^= data[1] << 8; case 1: h ^= data[0]; h *= m; } h ^= h >> 13; h *= m; h ^= h >> 15; return h; } } // namespace _ (private) } // namespace kj