/* * Copyright (c) Meta Platforms, Inc. and affiliates. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ // This is version 2 of SpookyHash, incompatible with version 1. // // SpookyHash: a 128-bit noncryptographic hash function // By Bob Jenkins, public domain // Oct 31 2010: alpha, framework + SpookyHash::Mix appears right // Oct 31 2011: alpha again, Mix only good to 2^^69 but rest appears right // Dec 31 2011: beta, improved Mix, tested it for 2-bit deltas // Feb 2 2012: production, same bits as beta // Feb 5 2012: adjusted definitions of uint* to be more portable // Mar 30 2012: 3 bytes/cycle, not 4. Alpha was 4 but wasn't thorough enough. // August 5 2012: SpookyV2 (different results) // // Up to 3 bytes/cycle for long messages. Reasonably fast for short messages. // All 1 or 2 bit deltas achieve avalanche within 1% bias per output bit. // // This was developed for and tested on 64-bit x86-compatible processors. // It assumes the processor is little-endian. There is a macro // controlling whether unaligned reads are allowed (by default they are). // This should be an equally good hash on big-endian machines, but it will // compute different results on them than on little-endian machines. // // Google's CityHash has similar specs to SpookyHash, and CityHash is faster // on new Intel boxes. MD4 and MD5 also have similar specs, but they are orders // of magnitude slower. CRCs are two or more times slower, but unlike // SpookyHash, they have nice math for combining the CRCs of pieces to form // the CRCs of wholes. There are also cryptographic hashes, but those are even // slower than MD5. // #pragma once #include <cassert> #include <cstddef> #include <cstdint> #include <folly/CPortability.h> #include <folly/Portability.h> #include <folly/lang/CString.h> namespace folly { namespace hash { // clang-format off class SpookyHashV2 { … }; // clang-format on } // namespace hash } // namespace folly
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