text: /*
   * libjingle
   * Copyright 2014 Google Inc.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   *  1. Redistributions of source code must retain the above copyright notice,
   *     this list of conditions and the following disclaimer.
   *  2. Redistributions in binary form must reproduce the above copyright notice,
   *     this list of conditions and the following disclaimer in the documentation
   *     and/or other materials provided with the distribution.
   *  3. The name of the author may not be used to endorse or promote products
   *     derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
   * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
   * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
   * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
   * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #ifndef TALK_BASE_ASYNCINVOKER_H_
  #define TALK_BASE_ASYNCINVOKER_H_
  
  #include "talk/base/asyncinvoker-inl.h"
  #include "talk/base/bind.h"
  #include "talk/base/sigslot.h"
  #include "talk/base/scopedptrcollection.h"
  #include "talk/base/thread.h"
  
  namespace talk_base {
  
  // Invokes function objects (aka functors) asynchronously on a Thread, and
  // owns the lifetime of calls (ie, when this object is destroyed, calls in
  // flight are cancelled). AsyncInvoker can optionally execute a user-specified
  // function when the asynchronous call is complete, or operates in
  // fire-and-forget mode otherwise.
  //
  // AsyncInvoker does not own the thread it calls functors on.
  //
  // A note about async calls and object lifetimes: users should
  // be mindful of object lifetimes when calling functions asynchronously and
  // ensure objects used by the function _cannot_ be deleted between the
  // invocation and execution of the functor. AsyncInvoker is designed to
  // help: any calls in flight will be cancelled when the AsyncInvoker used to
  // make the call is destructed, and any calls executing will be allowed to
  // complete before AsyncInvoker destructs.
  //
  // The easiest way to ensure lifetimes are handled correctly is to create a
  // class that owns the Thread and AsyncInvoker objects, and then call its
  // methods asynchronously as needed.
  //
  // Example:
  //   class MyClass {
  //    public:
  //     void FireAsyncTaskWithResult(Thread* thread, int x) {
  //       // Specify a callback to get the result upon completion.
  //       invoker_.AsyncInvoke<int>(
  //           thread, Bind(&MyClass::AsyncTaskWithResult, this, x),
  //           &MyClass::OnTaskComplete, this);
  //     }
  //     void FireAnotherAsyncTask(Thread* thread) {
  //       // No callback specified means fire-and-forget.
  //       invoker_.AsyncInvoke<void>(
  //           thread, Bind(&MyClass::AnotherAsyncTask, this));
  //
  //    private:
  //     int AsyncTaskWithResult(int x) {
  //       // Some long running process...
  //       return x * x;
  //     }
  //     void AnotherAsyncTask() {
  //       // Some other long running process...
  //     }
  //     void OnTaskComplete(int result) { result_ = result; }
  //
  //     AsyncInvoker invoker_;
  //     int result_;
  //   };
  class AsyncInvoker : public MessageHandler {
   public:
    AsyncInvoker();
    virtual ~AsyncInvoker();
  
    // Call |functor| asynchronously on |thread|, with no callback upon
    // completion. Returns immediately.
    template <class ReturnT, class FunctorT>
    void AsyncInvoke(Thread* thread,
                     const FunctorT& functor,
                     uint32 id = 0) {
      AsyncClosure* closure =
          new RefCountedObject<FireAndForgetAsyncClosure<FunctorT> >(functor);
      DoInvoke(thread, closure, id);
    }
  
    // Call |functor| asynchronously on |thread|, calling |callback| when done.
    template <class ReturnT, class FunctorT, class HostT>
    void AsyncInvoke(Thread* thread,
                     const FunctorT& functor,
                     void (HostT::*callback)(ReturnT),
                     HostT* callback_host,
                     uint32 id = 0) {
      AsyncClosure* closure =
          new RefCountedObject<NotifyingAsyncClosure<ReturnT, FunctorT, HostT> >(
              this, Thread::Current(), functor, callback, callback_host);
      DoInvoke(thread, closure, id);
    }
  
    // Call |functor| asynchronously on |thread|, calling |callback| when done.
    // Overloaded for void return.
    template <class ReturnT, class FunctorT, class HostT>
    void AsyncInvoke(Thread* thread,
                     const FunctorT& functor,
                     void (HostT::*callback)(),
                     HostT* callback_host,
                     uint32 id = 0) {
      AsyncClosure* closure =
          new RefCountedObject<NotifyingAsyncClosure<void, FunctorT, HostT> >(
              this, Thread::Current(), functor, callback, callback_host);
      DoInvoke(thread, closure, id);
    }
  
    // Synchronously execute on |thread| all outstanding calls we own
    // that are pending on |thread|, and wait for calls to complete
    // before returning. Optionally filter by message id.
    // The destructor will not wait for outstanding calls, so if that
    // behavior is desired, call Flush() before destroying this object.
    void Flush(Thread* thread, uint32 id = MQID_ANY);
  
    // Signaled when this object is destructed.
    sigslot::signal0<> SignalInvokerDestroyed;
  
   private:
    virtual void OnMessage(Message* msg);
    void DoInvoke(Thread* thread, AsyncClosure* closure, uint32 id);
  
    bool destroying_;
  
    DISALLOW_COPY_AND_ASSIGN(AsyncInvoker);
  };
  
  }  // namespace talk_base
  
  
  #endif  // TALK_BASE_ASYNCINVOKER_H_
  