// 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 #include #include #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 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 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 ReadTokenFromPickle( PickleIterator* pickle_iterator); } // namespace base #endif // BASE_TOKEN_H_