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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <map>
#include <memory>
#include <string>
#include <vector>
#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "base/threading/thread_checker.h"
#include "media/remoting/rpc.pb.h"
namespace media {
namespace remoting {
// Utility class to process incoming and outgoing RPC message to desired
// components on both end points. On sender side, for outgoing message, sender
// sends RPC message with associated handle value. On receiver side, for
// component which is interested in this RPC message has to register itself to
// RpcBroker. Before the RPC transmission starts, both sender and receiver need
// to negotiate the handle value in the existing RPC communication channel using
// handle kAcquireHandle.
// The class doesn't actually send RPC message to remote end point. Actual
// sender needs to set SendMessageCallback to RpcBroker. The class doesn't
// actually receive RPC message from the remote end point, either. Actually
// receiver needs to call ProcessMessageFromRemote() when RPC message is
// received. RpcBroker will distribute each RPC message to the components based
// on the handle value in the RPC message.
// Note this is single-threaded class running on main thread. It provides
// WeakPtr() for caller to post tasks to the main thread.
class RpcBroker {
using SendMessageCallback =
explicit RpcBroker(const SendMessageCallback& send_message_cb);
// Get unique handle value (larger than 0) for RPC message handles.
int GetUniqueHandle();
using ReceiveMessageCallback =
// Register a component to receive messages via the given
// ReceiveMessageCallback. |handle| is a unique handle value provided by a
// prior call to GetUniqueHandle() and is used to reference the component in
// the RPC messages. The receiver can then use it to direct an RPC message
// back to a specific component.
void RegisterMessageReceiverCallback(int handle,
const ReceiveMessageCallback& callback);
// Allows components to unregister in order to stop receiving message.
void UnregisterMessageReceiverCallback(int handle);
// Allows RpcBroker to distribute incoming RPC message to desired components.
void ProcessMessageFromRemote(std::unique_ptr<pb::RpcMessage> message);
// Sends RPC message to remote end point. The actually sender which sets
// SendMessageCallback to RpcBrokwer will receive RPC message to do actual
// data transmission.
void SendMessageToRemote(std::unique_ptr<pb::RpcMessage> message);
// Gets weak pointer of RpcBroker. This allows callers to post tasks to
// RpcBroker on the main thread.
base::WeakPtr<RpcBroker> GetWeakPtr();
// Overwrites |send_message_cb_|. This is used only for test purposes.
void SetMessageCallbackForTesting(const SendMessageCallback& send_message_cb);
// Predefined invalid handle value for RPC message.
static constexpr int kInvalidHandle = -1;
// Predefined handle value for RPC messages related to initialization (before
// the receiver handle(s) are known).
static constexpr int kAcquireHandle = 0;
// The first handle to return from GetUniqueHandle().
static constexpr int kFirstHandle = 1;
// Checks that all method calls occur on the same thread.
base::ThreadChecker thread_checker_;
// Next unique handle to return from GetUniqueHandle().
int next_handle_;
// Maps to hold handle value associated to MessageReceiver.
std::map<int, ReceiveMessageCallback> receive_callbacks_;
// Callback that is run to send a serialized message.
SendMessageCallback send_message_cb_;
base::WeakPtrFactory<RpcBroker> weak_factory_;
} // namespace remoting
} // namespace media