stop_token.h

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#ifndef YAZE_UTIL_STOP_TOKEN_H_
#define YAZE_UTIL_STOP_TOKEN_H_
 
#include <atomic>
#include <memory>
#include <utility>
 
namespace yaze::util {
 
struct NoStopStateTag {};
inline constexpr NoStopStateTag kNoStopState{};
 
// Poll-only cancellation for background scans. Some supported libc++ versions
// lack std::stop_token; the scans do not need stop callbacks or std::jthread.
class StopToken {
 public:
  StopToken() = default;
 
  bool has_stop_state() const noexcept { return state_ != nullptr; }
 
  bool stop_requested() const noexcept {
    return state_ && state_->load(std::memory_order_acquire);
  }
 
 private:
  friend class StopSource;
  explicit StopToken(std::shared_ptr<std::atomic<bool>> state)
      : state_(std::move(state)) {}
 
  std::shared_ptr<std::atomic<bool>> state_;
};
 
class StopSource {
 public:
  StopSource() : state_(std::make_shared<std::atomic<bool>>(false)) {}
  explicit StopSource(NoStopStateTag) noexcept {}
 
  StopToken get_token() const noexcept { return StopToken(state_); }
 
  bool request_stop() noexcept {
    return state_ && !state_->exchange(true, std::memory_order_acq_rel);
  }
 
 private:
  std::shared_ptr<std::atomic<bool>> state_;
};
 
}  // namespace yaze::util
 
#endif  // YAZE_UTIL_STOP_TOKEN_H_