guard_state.hpp

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#pragma once
 
#include <yaclib/log.hpp>
 
#include <cstdint>
 
namespace yaclib::detail {
 
class GuardState {
  static constexpr auto kMask = ~std::uintptr_t{1};
 
 public:
  GuardState() noexcept = default;
 
  explicit GuardState(void* ptr, bool owns) noexcept
    : _state{reinterpret_cast<std::uintptr_t>(ptr) | static_cast<std::uintptr_t>(owns)} {
  }
 
  GuardState(GuardState&& other) noexcept : _state{other._state} {
    other._state &= kMask;
  }
 
  GuardState& operator=(GuardState&& other) noexcept {
    Swap(other);
    return *this;
  }
 
  void Swap(GuardState& other) noexcept {
    std::swap(_state, other._state);
  }
 
  void* Ptr() const {
    return reinterpret_cast<void*>(_state & kMask);
  }
 
  bool Owns() const noexcept {
    return (_state & 1U) != 0;
  }
 
  void* LockState() noexcept {
    YACLIB_DEBUG(Owns(), "Cannot lock locked guard");
    _state |= 1U;
    return Ptr();
  }
 
  void* UnlockState() noexcept {
    YACLIB_DEBUG(!Owns(), "Cannot unlock not locked guard");
    _state &= kMask;
    return Ptr();
  }
 
  void* ReleaseState() noexcept {
    void* was = Ptr();
    _state = 0;
    return was;
  }
 
 protected:
  std::uintptr_t _state = 0;
};
 
}  // namespace yaclib::detail