22161b7547
Summary: With expected use for a 128-bit hash, xxhash library is upgraded to current dev (2c611a76f914828bed675f0f342d6c4199ffee1e) as of Aug 6 so that we can use production version of XXH3_128bits as new Hash128 function (added in hash128.h). To make this work, however, we have to carve out the "preview" version of XXH3 that is used in new SST Bloom and Ribbon filters, since that will not get maintenance in xxhash releases. I have consolidated all the relevant code into xxph3.h and made it "inline only" (no .cc file). The working name for this hash function is changed from XXH3p to XXPH3 (XX Preview Hash) because the latter is easier to get working with no symbol name conflicts between the headers. Pull Request resolved: https://github.com/facebook/rocksdb/pull/8634 Test Plan: no expected change in existing functionality. For Hash128, added some unit tests based on those for Hash64 to ensure some basic properties and that the values do not change accidentally. Reviewed By: zhichao-cao Differential Revision: D30173490 Pulled By: pdillinger fbshipit-source-id: 06aa542a7a28b353bc2c865b9b2f8bdfe44158e4
119 lines
4.2 KiB
C++
119 lines
4.2 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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//
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// Common hash functions with convenient interfaces. If hashing a
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// statically-sized input in a performance-critical context, consider
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// calling a specific hash implementation directly, such as
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// XXH3_64bits from xxhash.h.
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//
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// Since this is a very common header, implementation details are kept
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// out-of-line. Out-of-lining also aids in tracking the time spent in
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// hashing functions. Inlining is of limited benefit for runtime-sized
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// hash inputs.
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#pragma once
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#include <cstddef>
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#include <cstdint>
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#include "rocksdb/slice.h"
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#include "util/fastrange.h"
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namespace ROCKSDB_NAMESPACE {
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// Stable/persistent 64-bit hash. Higher quality and generally faster than
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// Hash(), especially for inputs > 24 bytes.
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// KNOWN FLAW: incrementing seed by 1 might not give sufficiently independent
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// results from previous seed. Recommend incrementing by a large odd number.
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extern uint64_t Hash64(const char* data, size_t n, uint64_t seed);
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// Specific optimization without seed (same as seed = 0)
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extern uint64_t Hash64(const char* data, size_t n);
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// Non-persistent hash. Must only used for in-memory data structures.
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// The hash results are thus subject to change between releases,
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// architectures, build configuration, etc. (Thus, it rarely makes sense
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// to specify a seed for this function, except for a "rolling" hash.)
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// KNOWN FLAW: incrementing seed by 1 might not give sufficiently independent
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// results from previous seed. Recommend incrementing by a large odd number.
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inline uint64_t NPHash64(const char* data, size_t n, uint64_t seed) {
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#ifdef ROCKSDB_MODIFY_NPHASH
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// For testing "subject to change"
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return Hash64(data, n, seed + 123456789);
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#else
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// Currently same as Hash64
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return Hash64(data, n, seed);
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#endif
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}
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// Specific optimization without seed (same as seed = 0)
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inline uint64_t NPHash64(const char* data, size_t n) {
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#ifdef ROCKSDB_MODIFY_NPHASH
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// For testing "subject to change"
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return Hash64(data, n, 123456789);
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#else
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// Currently same as Hash64
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return Hash64(data, n);
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#endif
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}
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// Stable/persistent 32-bit hash. Moderate quality and high speed on
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// small inputs.
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// TODO: consider rename to Hash32
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// KNOWN FLAW: incrementing seed by 1 might not give sufficiently independent
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// results from previous seed. Recommend pseudorandom or hashed seeds.
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extern uint32_t Hash(const char* data, size_t n, uint32_t seed);
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// TODO: consider rename to LegacyBloomHash32
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inline uint32_t BloomHash(const Slice& key) {
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return Hash(key.data(), key.size(), 0xbc9f1d34);
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}
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inline uint64_t GetSliceHash64(const Slice& key) {
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return Hash64(key.data(), key.size());
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}
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// Provided for convenience for use with template argument deduction, where a
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// specific overload needs to be used.
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extern uint64_t (*kGetSliceNPHash64UnseededFnPtr)(const Slice&);
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inline uint64_t GetSliceNPHash64(const Slice& s) {
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return NPHash64(s.data(), s.size());
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}
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inline uint64_t GetSliceNPHash64(const Slice& s, uint64_t seed) {
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return NPHash64(s.data(), s.size(), seed);
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}
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// Similar to `GetSliceNPHash64()` with `seed`, but input comes from
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// concatenation of `Slice`s in `data`.
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extern uint64_t GetSlicePartsNPHash64(const SliceParts& data, uint64_t seed);
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inline size_t GetSliceRangedNPHash(const Slice& s, size_t range) {
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return FastRange64(NPHash64(s.data(), s.size()), range);
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}
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// TODO: consider rename to GetSliceHash32
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inline uint32_t GetSliceHash(const Slice& s) {
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return Hash(s.data(), s.size(), 397);
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}
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// Useful for splitting up a 64-bit hash
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inline uint32_t Upper32of64(uint64_t v) {
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return static_cast<uint32_t>(v >> 32);
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}
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inline uint32_t Lower32of64(uint64_t v) { return static_cast<uint32_t>(v); }
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// std::hash compatible interface.
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// TODO: consider rename to SliceHasher32
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struct SliceHasher {
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uint32_t operator()(const Slice& s) const { return GetSliceHash(s); }
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};
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} // namespace ROCKSDB_NAMESPACE
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