fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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90 lines
3.0 KiB
90 lines
3.0 KiB
// 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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// XXH3p_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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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 structure.
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// The hash results are thus applicable to change. (Thus, it rarely makes
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// sense to specify a seed for this function.)
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inline uint64_t NPHash64(const char* data, size_t n, uint32_t seed) {
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// Currently same as Hash64
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return Hash64(data, n, seed);
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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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// Currently same as Hash64
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return Hash64(data, n);
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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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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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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 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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