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- // Copyright 2018 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #ifndef BASE_TOKEN_H_
- #define BASE_TOKEN_H_
- #include <stdint.h>
- #include <string>
- #include <tuple>
- #include "base/base_export.h"
- #include "base/containers/span.h"
- #include "base/hash/hash.h"
- #include "third_party/abseil-cpp/absl/types/optional.h"
- namespace base {
- // A Token is a randomly chosen 128-bit integer. This class supports generation
- // from a cryptographically strong random source, or constexpr construction over
- // fixed values (e.g. to store a pre-generated constant value). Tokens are
- // similar in spirit and purpose to UUIDs, without many of the constraints and
- // expectations (such as byte layout and string representation) clasically
- // associated with UUIDs.
- class BASE_EXPORT Token {
- public:
- // Constructs a zero Token.
- constexpr Token() = default;
- // Constructs a Token with |high| and |low| as its contents.
- constexpr Token(uint64_t high, uint64_t low) : words_{high, low} {}
- constexpr Token(const Token&) = default;
- constexpr Token& operator=(const Token&) = default;
- constexpr Token(Token&&) noexcept = default;
- constexpr Token& operator=(Token&&) = default;
- // Constructs a new Token with random |high| and |low| values taken from a
- // cryptographically strong random source.
- static Token CreateRandom();
- // The high and low 64 bits of this Token.
- constexpr uint64_t high() const { return words_[0]; }
- constexpr uint64_t low() const { return words_[1]; }
- constexpr bool is_zero() const { return words_[0] == 0 && words_[1] == 0; }
- span<const uint8_t, 16> AsBytes() const {
- return as_bytes(make_span(words_));
- }
- constexpr bool operator==(const Token& other) const {
- return words_[0] == other.words_[0] && words_[1] == other.words_[1];
- }
- constexpr bool operator!=(const Token& other) const {
- return !(*this == other);
- }
- constexpr bool operator<(const Token& other) const {
- return std::tie(words_[0], words_[1]) <
- std::tie(other.words_[0], other.words_[1]);
- }
- // Generates a string representation of this Token useful for e.g. logging.
- std::string ToString() const;
- // FromString is the opposite of ToString. It returns absl::nullopt if the
- // |string_representation| is invalid.
- static absl::optional<Token> FromString(StringPiece string_representation);
- private:
- // Note: Two uint64_t are used instead of uint8_t[16] in order to have a
- // simpler implementation, paricularly for |ToString()|, |is_zero()|, and
- // constexpr value construction.
- uint64_t words_[2] = {0, 0};
- };
- // For use in std::unordered_map.
- struct TokenHash {
- size_t operator()(const base::Token& token) const {
- return base::HashInts64(token.high(), token.low());
- }
- };
- class Pickle;
- class PickleIterator;
- // For serializing and deserializing Token values.
- BASE_EXPORT void WriteTokenToPickle(Pickle* pickle, const Token& token);
- BASE_EXPORT absl::optional<Token> ReadTokenFromPickle(
- PickleIterator* pickle_iterator);
- } // namespace base
- #endif // BASE_TOKEN_H_
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