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* Copyright 2012 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.
// This file contains interfaces for DataChannels
#include <stddef.h>
#include <stdint.h>
#include <string>
#include "absl/functional/any_invocable.h"
#include "absl/types/optional.h"
#include "api/priority.h"
#include "api/ref_count.h"
#include "api/rtc_error.h"
#include "rtc_base/checks.h"
#include "rtc_base/copy_on_write_buffer.h"
#include "rtc_base/system/rtc_export.h"
namespace webrtc {
// C++ version of:
// TODO(deadbeef): Use absl::optional for the "-1 if unset" things.
struct DataChannelInit {
// Deprecated. Reliability is assumed, and channel will be unreliable if
// maxRetransmitTime or MaxRetransmits is set.
bool reliable = false;
// True if ordered delivery is required.
bool ordered = true;
// The max period of time in milliseconds in which retransmissions will be
// sent. After this time, no more retransmissions will be sent.
// Cannot be set along with `maxRetransmits`.
// This is called `maxPacketLifeTime` in the WebRTC JS API.
// Negative values are ignored, and positive values are clamped to [0-65535]
absl::optional<int> maxRetransmitTime;
// The max number of retransmissions.
// Cannot be set along with `maxRetransmitTime`.
// Negative values are ignored, and positive values are clamped to [0-65535]
absl::optional<int> maxRetransmits;
// This is set by the application and opaque to the WebRTC implementation.
std::string protocol;
// True if the channel has been externally negotiated and we do not send an
// in-band signalling in the form of an "open" message. If this is true, `id`
// below must be set; otherwise it should be unset and will be negotiated
// in-band.
bool negotiated = false;
// The stream id, or SID, for SCTP data channels. -1 if unset (see above).
int id = -1;
absl::optional<Priority> priority;
// At the JavaScript level, data can be passed in as a string or a blob, so
// this structure's `binary` flag tells whether the data should be interpreted
// as binary or text.
struct DataBuffer {
DataBuffer(const rtc::CopyOnWriteBuffer& data, bool binary)
: data(data), binary(binary) {}
// For convenience for unit tests.
explicit DataBuffer(const std::string& text)
: data(, text.length()), binary(false) {}
size_t size() const { return data.size(); }
rtc::CopyOnWriteBuffer data;
// Indicates if the received data contains UTF-8 or binary data.
// Note that the upper layers are left to verify the UTF-8 encoding.
// TODO(jiayl): prefer to use an enum instead of a bool.
bool binary;
// Used to implement RTCDataChannel events.
// The code responding to these callbacks should unwind the stack before
// using any other webrtc APIs; re-entrancy is not supported.
class DataChannelObserver {
// The data channel state have changed.
virtual void OnStateChange() = 0;
// A data buffer was successfully received.
virtual void OnMessage(const DataBuffer& buffer) = 0;
// The data channel's buffered_amount has changed.
virtual void OnBufferedAmountChange(uint64_t sent_data_size) {}
// Override this to get callbacks directly on the network thread.
// An implementation that does that must not block the network thread
// but rather only use the callback to trigger asynchronous processing
// elsewhere as a result of the notification.
// The default return value, `false`, means that notifications will be
// delivered on the signaling thread associated with the peerconnection
// instance.
// TODO(webrtc:11547): Eventually all DataChannelObserver implementations
// should be called on the network thread and this method removed.
virtual bool IsOkToCallOnTheNetworkThread() { return false; }
virtual ~DataChannelObserver() = default;
class RTC_EXPORT DataChannelInterface : public RefCountInterface {
// C++ version of:
// Unlikely to change, but keep in sync with and
// RTCDataChannel.h:RTCDataChannelState.
enum DataState {
kOpen, // The DataChannel is ready to send data.
static const char* DataStateString(DataState state) {
switch (state) {
case kConnecting:
return "connecting";
case kOpen:
return "open";
case kClosing:
return "closing";
case kClosed:
return "closed";
RTC_CHECK(false) << "Unknown DataChannel state: " << state;
return "";
// Used to receive events from the data channel. Only one observer can be
// registered at a time. UnregisterObserver should be called before the
// observer object is destroyed.
virtual void RegisterObserver(DataChannelObserver* observer) = 0;
virtual void UnregisterObserver() = 0;
// The label attribute represents a label that can be used to distinguish this
// DataChannel object from other DataChannel objects.
virtual std::string label() const = 0;
// The accessors below simply return the properties from the DataChannelInit
// the data channel was constructed with.
virtual bool reliable() const = 0;
// TODO(deadbeef): Remove these dummy implementations when all classes have
// implemented these APIs. They should all just return the values the
// DataChannel was created with.
virtual bool ordered() const;
// TODO(hta): Deprecate and remove the following two functions.
virtual uint16_t maxRetransmitTime() const;
virtual uint16_t maxRetransmits() const;
virtual absl::optional<int> maxRetransmitsOpt() const;
virtual absl::optional<int> maxPacketLifeTime() const;
virtual std::string protocol() const;
virtual bool negotiated() const;
// Returns the ID from the DataChannelInit, if it was negotiated out-of-band.
// If negotiated in-band, this ID will be populated once the DTLS role is
// determined, and until then this will return -1.
virtual int id() const = 0;
virtual Priority priority() const { return Priority::kLow; }
virtual DataState state() const = 0;
// When state is kClosed, and the DataChannel was not closed using
// the closing procedure, returns the error information about the closing.
// The default implementation returns "no error".
virtual RTCError error() const { return RTCError(); }
virtual uint32_t messages_sent() const = 0;
virtual uint64_t bytes_sent() const = 0;
virtual uint32_t messages_received() const = 0;
virtual uint64_t bytes_received() const = 0;
// Returns the number of bytes of application data (UTF-8 text and binary
// data) that have been queued using Send but have not yet been processed at
// the SCTP level. See comment above Send below.
// Values are less or equal to MaxSendQueueSize().
virtual uint64_t buffered_amount() const = 0;
// Begins the graceful data channel closing procedure. See:
virtual void Close() = 0;
// Sends `data` to the remote peer. If the data can't be sent at the SCTP
// level (due to congestion control), it's buffered at the data channel level,
// up to a maximum of MaxSendQueueSize().
// Returns false if the data channel is not in open state or if the send
// buffer is full.
// TODO(webrtc:13289): Return an RTCError with information about the failure.
// TODO(tommi): Remove this method once downstream implementations don't refer
// to it.
virtual bool Send(const DataBuffer& buffer);
// Queues up an asynchronus send operation to run on a network thread.
// Once the operation has completed the `on_complete` callback is invoked,
// on the thread the send operation was done on. It's important that
// `on_complete` implementations do not block the current thread but rather
// post any expensive operations to other worker threads.
// TODO(tommi): Make pure virtual after updating mock class in Chromium.
// Deprecate `Send` in favor of this variant since the return value of `Send`
// is limiting for a fully async implementation (yet in practice is ignored).
virtual void SendAsync(DataBuffer buffer,
absl::AnyInvocable<void(RTCError) &&> on_complete);
// Amount of bytes that can be queued for sending on the data channel.
// Those are bytes that have not yet been processed at the SCTP level.
static uint64_t MaxSendQueueSize();
~DataChannelInterface() override = default;
} // namespace webrtc