mirror of
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95 lines
3.0 KiB
C++
95 lines
3.0 KiB
C++
// Copyright 2018 The Chromium Authors
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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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#ifdef UNSAFE_BUFFERS_BUILD
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// TODO(crbug.com/40284755): Remove this and spanify to fix the errors.
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#pragma allow_unsafe_buffers
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#endif
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#ifndef BASE_TOKEN_H_
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#define BASE_TOKEN_H_
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#include <stdint.h>
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#include <compare>
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#include <optional>
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#include <string>
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#include "base/base_export.h"
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#include "base/containers/span.h"
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#include "base/strings/string_piece.h"
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namespace base {
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// A Token is a randomly chosen 128-bit integer. This class supports generation
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// from a cryptographically strong random source, or constexpr construction over
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// fixed values (e.g. to store a pre-generated constant value). Tokens are
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// similar in spirit and purpose to UUIDs, without many of the constraints and
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// expectations (such as byte layout and string representation) clasically
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// associated with UUIDs.
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class BASE_EXPORT Token {
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public:
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// Constructs a zero Token.
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constexpr Token() = default;
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// Constructs a Token with |high| and |low| as its contents.
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constexpr Token(uint64_t high, uint64_t low) : words_{high, low} {}
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constexpr Token(const Token&) = default;
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constexpr Token& operator=(const Token&) = default;
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constexpr Token(Token&&) noexcept = default;
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constexpr Token& operator=(Token&&) = default;
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// Constructs a new Token with random |high| and |low| values taken from a
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// cryptographically strong random source. The result's |is_zero()| is
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// guaranteed to be false.
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static Token CreateRandom();
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// The high and low 64 bits of this Token.
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constexpr uint64_t high() const { return words_[0]; }
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constexpr uint64_t low() const { return words_[1]; }
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constexpr bool is_zero() const { return words_[0] == 0 && words_[1] == 0; }
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span<const uint8_t, 16> AsBytes() const {
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return as_bytes(make_span(words_));
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}
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friend constexpr auto operator<=>(const Token& lhs,
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const Token& rhs) = default;
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friend constexpr bool operator==(const Token& lhs,
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const Token& rhs) = default;
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// Generates a string representation of this Token useful for e.g. logging.
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std::string ToString() const;
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// FromString is the opposite of ToString. It returns std::nullopt if the
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// |string_representation| is invalid.
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static std::optional<Token> FromString(StringPiece string_representation);
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private:
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// Note: Two uint64_t are used instead of uint8_t[16] in order to have a
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// simpler implementation, paricularly for |ToString()|, |is_zero()|, and
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// constexpr value construction.
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uint64_t words_[2] = {0, 0};
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};
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// For use in std::unordered_map.
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struct BASE_EXPORT TokenHash {
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size_t operator()(const Token& token) const;
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};
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class Pickle;
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class PickleIterator;
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// For serializing and deserializing Token values.
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BASE_EXPORT void WriteTokenToPickle(Pickle* pickle, const Token& token);
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BASE_EXPORT std::optional<Token> ReadTokenFromPickle(
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PickleIterator* pickle_iterator);
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} // namespace base
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#endif // BASE_TOKEN_H_
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