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90 lines
3.3 KiB
90 lines
3.3 KiB
// Copyright 2020 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef CAST_STREAMING_RPC_BROKER_H_
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#define CAST_STREAMING_RPC_BROKER_H_
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#include <vector>
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#include "cast/streaming/remoting.pb.h"
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#include "util/flat_map.h"
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namespace openscreen {
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namespace cast {
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// Processes incoming and outgoing RPC messages and links them to desired
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// components on both end points. For outgoing messages, the messager
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// must send an RPC message with associated handle value. On the messagee side,
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// the message is sent to a pre-registered component using that handle.
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// Before RPC communication starts, both sides need to negotiate the handle
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// value in the existing RPC communication channel using the special handles
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// |kAcquire*Handle|.
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//
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// NOTE: RpcBroker doesn't actually send RPC messages to the remote. The session
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// messager needs to set SendMessageCallback, and call ProcessMessageFromRemote
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// as appropriate. The RpcBroker then distributes each RPC message to the
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// subscribed component.
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class RpcBroker {
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public:
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using Handle = int;
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using ReceiveMessageCallback = std::function<void(const RpcMessage&)>;
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using SendMessageCallback = std::function<void(std::vector<uint8_t>)>;
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explicit RpcBroker(SendMessageCallback send_message_cb);
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RpcBroker(const RpcBroker&) = delete;
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RpcBroker(RpcBroker&&) noexcept;
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RpcBroker& operator=(const RpcBroker&) = delete;
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RpcBroker& operator=(RpcBroker&&);
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~RpcBroker();
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// Get unique handle value for RPC message handles.
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Handle GetUniqueHandle();
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// Register a component to receive messages via the given
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// ReceiveMessageCallback. |handle| is a unique handle value provided by a
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// prior call to GetUniqueHandle() and is used to reference the component in
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// the RPC messages. The receiver can then use it to direct an RPC message
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// back to a specific component.
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void RegisterMessageReceiverCallback(Handle handle,
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ReceiveMessageCallback callback);
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// Allows components to unregister in order to stop receiving message.
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void UnregisterMessageReceiverCallback(Handle handle);
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// Distributes an incoming RPC message to the registered (if any) component.
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void ProcessMessageFromRemote(const RpcMessage& message);
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// Executes the |send_message_cb_| using |message|.
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void SendMessageToRemote(const RpcMessage& message);
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// Checks if the handle is registered for receiving messages. Test-only.
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bool IsRegisteredForTesting(Handle handle);
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// Predefined invalid handle value for RPC message.
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static constexpr Handle kInvalidHandle = -1;
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// Predefined handle values for RPC messages related to initialization (before
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// the receiver handle(s) are known).
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static constexpr Handle kAcquireRendererHandle = 0;
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static constexpr Handle kAcquireDemuxerHandle = 1;
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// The first handle to return from GetUniqueHandle().
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static constexpr Handle kFirstHandle = 100;
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private:
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// Next unique handle to return from GetUniqueHandle().
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Handle next_handle_;
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// Maps of handle values to associated MessageReceivers.
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FlatMap<Handle, ReceiveMessageCallback> receive_callbacks_;
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// Callback that is ran to send a serialized message.
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SendMessageCallback send_message_cb_;
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};
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} // namespace cast
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} // namespace openscreen
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#endif // CAST_STREAMING_RPC_BROKER_H_
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