chromium/net/disk_cache/blockfile/in_flight_io.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_DISK_CACHE_BLOCKFILE_IN_FLIGHT_IO_H_
#define NET_DISK_CACHE_BLOCKFILE_IN_FLIGHT_IO_H_

#include <set>

#include "base/check.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/ref_counted.h"
#include "base/synchronization/lock.h"
#include "base/synchronization/waitable_event.h"

namespace base {
class SequencedTaskRunner;
}  // namespace base

namespace disk_cache {

class InFlightIO;

// This class represents a single asynchronous IO operation while it is being
// bounced between threads.
class BackgroundIO : public base::RefCountedThreadSafe<BackgroundIO> { … };

// This class keeps track of asynchronous IO operations. A single instance
// of this class is meant to be used to start an asynchronous operation (using
// PostXX, exposed by a derived class). This class will post the operation to a
// worker thread, hanlde the notification when the operation finishes and
// perform the callback on the same thread that was used to start the operation.
//
// The regular sequence of calls is:
//                 Thread_1                          Worker_thread
//    1.     DerivedInFlightIO::PostXX()
//    2.                         -> PostTask ->
//    3.    InFlightIO::OnOperationPosted()
//    4.                                        DerivedBackgroundIO::XX()
//    5.                                         IO operation completes
//    6.                                       InFlightIO::OnIOComplete()
//    7.                         <- PostTask <-
//    8.  BackgroundIO::OnIOSignalled()
//    9.  InFlightIO::InvokeCallback()
//   10. DerivedInFlightIO::OnOperationComplete()
//   11.       invoke callback
//
// Shutdown is a special case that is handled though WaitForPendingIO() instead
// of just waiting for step 7.
class InFlightIO { … };

}  // namespace disk_cache

#endif  // NET_DISK_CACHE_BLOCKFILE_IN_FLIGHT_IO_H_