87 lines
3.0 KiB
C
87 lines
3.0 KiB
C
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// Copyright (c) 2011 The Chromium 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.
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#ifndef BASE_HASH_HASH_H_
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#define BASE_HASH_HASH_H_
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#include <stddef.h>
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#include <stdint.h>
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#include <limits>
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#include <string>
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#include <utility>
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#include "base/base_export.h"
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#include "base/containers/span.h"
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#include "base/logging.h"
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#include "base/strings/string16.h"
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#include "base/strings/string_piece.h"
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namespace base {
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// WARNING: This hash functions should not be used for any cryptographic
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// purpose.
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// Deprecated: Computes a hash of a memory buffer, use FastHash() instead.
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// If you need to persist a change on disk or between computers, use
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// PersistentHash().
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// TODO(https://crbug.com/1025358): Migrate client code to new hash function.
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BASE_EXPORT uint32_t Hash(const void* data, size_t length);
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BASE_EXPORT uint32_t Hash(const std::string& str);
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BASE_EXPORT uint32_t Hash(const string16& str);
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// Really *fast* and high quality hash.
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// Recommended hash function for general use, we pick the best performant
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// hash for each build target.
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// It is prone to be updated whenever a newer/faster hash function is
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// publicly available.
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// May changed without warning, do not expect stability of outputs.
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BASE_EXPORT size_t FastHash(base::span<const uint8_t> data);
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inline size_t FastHash(StringPiece str) {
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return FastHash(as_bytes(make_span(str)));
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}
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// Computes a hash of a memory buffer. This hash function must not change so
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// that code can use the hashed values for persistent storage purposes or
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// sending across the network. If a new persistent hash function is desired, a
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// new version will have to be added in addition.
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//
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// WARNING: This hash function should not be used for any cryptographic purpose.
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BASE_EXPORT uint32_t PersistentHash(base::span<const uint8_t> data);
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BASE_EXPORT uint32_t PersistentHash(const void* data, size_t length);
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BASE_EXPORT uint32_t PersistentHash(const std::string& str);
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// Hash pairs of 32-bit or 64-bit numbers.
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BASE_EXPORT size_t HashInts32(uint32_t value1, uint32_t value2);
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BASE_EXPORT size_t HashInts64(uint64_t value1, uint64_t value2);
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template <typename T1, typename T2>
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inline size_t HashInts(T1 value1, T2 value2) {
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// This condition is expected to be compile-time evaluated and optimised away
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// in release builds.
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if (sizeof(T1) > sizeof(uint32_t) || (sizeof(T2) > sizeof(uint32_t)))
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return HashInts64(value1, value2);
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return HashInts32(static_cast<uint32_t>(value1),
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static_cast<uint32_t>(value2));
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}
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// A templated hasher for pairs of integer types. Example:
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//
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// using MyPair = std::pair<int32_t, int32_t>;
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// std::unordered_set<MyPair, base::IntPairHash<MyPair>> set;
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template <typename T>
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struct IntPairHash;
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template <typename Type1, typename Type2>
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struct IntPairHash<std::pair<Type1, Type2>> {
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size_t operator()(std::pair<Type1, Type2> value) const {
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return HashInts(value.first, value.second);
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}
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};
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} // namespace base
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#endif // BASE_HASH_HASH_H_
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