mem_lock.h

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/*
 * Copyright 2015 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http:///www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


#ifndef PAGESPEED_KERNEL_BASE_MEM_LOCK_H_
#define PAGESPEED_KERNEL_BASE_MEM_LOCK_H_

#include "pagespeed/kernel/base/basictypes.h"
#include "pagespeed/kernel/base/named_lock_manager.h"
#include "pagespeed/kernel/base/string.h"

namespace net_instaweb {

class Function;
class MemLockState;

class MemLock : public NamedLock {
 public:
  static const int64 kDoNotSteal = -1;
  static const int64 kNotHeld = -1;
  static const int64 kNotPending = -1;

  virtual void LockTimedWait(int64 wait_ms, Function* callback);
  virtual void LockTimedWaitStealOld(int64 wait_ms, int64 steal_ms,
                                     Function* callback);
  virtual void Unlock();
  virtual GoogleString name() const;
  virtual bool Held() { return grant_time_ms_ != kNotHeld; }

  void Wakeup();

  int64 wakeup_time_ms() const { return wakeup_time_ms_; }

  int StableCompare(const MemLock* that) const;

 private:
  friend class MemLockState;

  MemLock(int64 sequence, MemLockState* lock_state);
  virtual ~MemLock();

  int64 grant_time_ms() const { return grant_time_ms_; }

  int64 steal_ms() const { return steal_ms_; }

  void Grant(int64 grant_time_ms);

  void Deny();

  void CalculateWakeupTime(int64 held_lock_grant_time_ms);

  bool CanSteal() const { return steal_ms_ != kDoNotSteal; }

  bool IsPending() const { return wakeup_time_ms_ != kNotPending; }

  void Clear();

  bool ShouldCancelOnWakeup() const {
    return cancel_time_ms_ == wakeup_time_ms_;
  }

  MemLockState* lock_state_;
  Function* callback_;

  int64 cancel_time_ms_; 
  int64 grant_time_ms_; 
  int64 sequence_; 

  int64 steal_ms_; 
  int64 wakeup_time_ms_; 
};

}  

#endif