data_track_stream.h

/*
 * Copyright 2026 LiveKit
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
#pragma once
 
#include <condition_variable>
#include <cstdint>
#include <mutex>
#include <optional>
 
#include "livekit/data_track_error.h"
#include "livekit/data_track_frame.h"
#include "livekit/ffi_handle.h"
#include "livekit/visibility.h"
 
namespace livekit {
 
namespace proto {
class FfiEvent;
class DataTrackStreamReadResponse;
} // namespace proto
 
class LIVEKIT_API DataTrackStream {
public:
  struct Options {
    std::optional<std::uint32_t> buffer_size{std::nullopt};
  };
 
  virtual ~DataTrackStream();
 
  DataTrackStream(const DataTrackStream&) = delete;
  DataTrackStream& operator=(const DataTrackStream&) = delete;
  // The FFI listener captures `this`, so moving the object would leave the
  // registered callback pointing at the old address.
  DataTrackStream(DataTrackStream&&) noexcept = delete;
  // Instances are created and returned as std::shared_ptr, so value-move
  // support is not required by the current API.
  DataTrackStream& operator=(DataTrackStream&&) noexcept = delete;
 
  bool read(DataTrackFrame& out);
 
  std::optional<SubscribeDataTrackError> terminalError() const;
 
  void close();
 
private:
  friend class RemoteDataTrack;
#ifdef LIVEKIT_TEST_ACCESS
  friend class DataTrackStreamTest;
#endif
 
  DataTrackStream() = default;
  void init(FfiHandle subscription_handle);
 
  void onFfiEvent(const proto::FfiEvent& event);
 
  void handleReadResponse(const proto::DataTrackStreamReadResponse& response);
 
  void failProtocolError(const char* message);
 
  void pushFrame(DataTrackFrame&& frame);
 
  void pushEos(std::optional<SubscribeDataTrackError> error = std::nullopt);
 
  mutable std::mutex mutex_;
 
  std::condition_variable cv_;
 
  std::optional<DataTrackFrame> frame_;
 
  bool eof_{false};
 
  bool closed_{false};
 
  std::optional<SubscribeDataTrackError> terminal_error_;
 
  FfiHandle subscription_handle_;
 
  std::int32_t listener_id_{-1};
};
 
} // namespace livekit