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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef mozilla_ipc_SendStream_h
#define mozilla_ipc_SendStream_h
#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/ipc/PSendStreamChild.h"
#include "mozilla/ipc/PSendStreamParent.h"
class nsIInputStream;
class nsIAsyncInputStream;
namespace mozilla {
namespace dom {
class nsIContentChild;
} // dom namespace
namespace ipc {
class PBackgroundChild;
// The SendStream IPC actor is designed to push an nsIInputStream from child to
// parent incrementally. This is mainly needed for streams such as nsPipe that
// may not yet have all their data available when the stream must be sent across
// an IPC boundary. While many streams are handled by SerializeInputStream(),
// these streams cannot be serialized and must be sent using this actor.
//
// The SendStream actor only supports sending data from child to parent.
//
// The SendStream actor only support async, non-blocking streams because they
// must be read inline on the main thread and Worker threads.
//
// In general, the creation and handling of the SendStream actor cannot be
// abstracted away behind SerializeInputStream() because the actor must be
// carefully managed. Specifically:
//
// 1) The data flow must be explicitly initiated by calling
// SendStreamChild::Start() after the actor has been sent to the parent.
// 2) If the actor is never sent to the parent, then the child code must
// call SendStreamChild::StartDestroy() to avoid memory leaks.
// 3) The SendStreamChild actor can only be used on threads that can be
// guaranteed to stay alive as long as the actor is alive. Right now
// this limits SendStream to the main thread and Worker threads.
//
// In general you should probably use the AutoIPCStreamChild RAII class
// defined in InputStreamUtils.h instead of using SendStreamChild directly.
class SendStreamChild : public PSendStreamChild
{
public:
// Create a SendStreamChild using a PContent IPC manager on the
// main thread. This can return nullptr if the provided stream is
// blocking.
static SendStreamChild*
Create(nsIAsyncInputStream* aInputStream, dom::nsIContentChild* aManager);
// Create a SendStreamChild using a PBackground IPC manager on the
// main thread or a Worker thread. This can return nullptr if the provided
// stream is blocking or if the Worker thread is already shutting down.
static SendStreamChild*
Create(nsIAsyncInputStream* aInputStream, PBackgroundChild* aManager);
// Start reading data from the nsIAsyncInputStream used to create the actor.
// This must be called after the actor is passed to the parent. If you
// use AutoIPCStream this is handled automatically.
virtual void
Start() = 0;
// Start cleaning up the actor. This must be called if the actor is never
// sent to the parent. If you use AutoIPCStream this is handled
// automatically.
virtual void
StartDestroy() = 0;
protected:
virtual
~SendStreamChild() = 0;
};
// On the parent side, you must simply call TakeReader() upon receiving a
// reference to the SendStreamParent actor. You do not need to maintain a
// reference to the actor itself.
class SendStreamParent : public PSendStreamParent
{
public:
virtual already_AddRefed<nsIInputStream>
TakeReader() = 0;
protected:
virtual
~SendStreamParent() = 0;
};
} // namespace ipc
} // namespace mozilla
#endif // mozilla_ipc_SendStream_h
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