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/*
* Copyright 2014 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef WEBRTC_BASE_ASYNCINVOKER_H_
#define WEBRTC_BASE_ASYNCINVOKER_H_
#include "webrtc/base/asyncinvoker-inl.h"
#include "webrtc/base/bind.h"
#include "webrtc/base/sigslot.h"
#include "webrtc/base/scopedptrcollection.h"
#include "webrtc/base/thread.h"
namespace rtc {
// 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 rtc
#endif // WEBRTC_BASE_ASYNCINVOKER_H_
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