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/*
* Copyright (c) 2021 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.
*/
#ifndef NET_DCSCTP_SOCKET_CALLBACK_DEFERRER_H_
#define NET_DCSCTP_SOCKET_CALLBACK_DEFERRER_H_
#include <cstdint>
#include <functional>
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "absl/strings/string_view.h"
#include "api/array_view.h"
#include "api/ref_counted_base.h"
#include "api/scoped_refptr.h"
#include "net/dcsctp/public/dcsctp_message.h"
#include "net/dcsctp/public/dcsctp_socket.h"
#include "rtc_base/ref_counted_object.h"
namespace dcsctp {
// Defers callbacks until they can be safely triggered.
//
// There are a lot of callbacks from the dcSCTP library to the client,
// such as when messages are received or streams are closed. When the client
// receives these callbacks, the client is expected to be able to call into the
// library - from within the callback. For example, sending a reply message when
// a certain SCTP message has been received, or to reconnect when the connection
// was closed for any reason. This means that the dcSCTP library must always be
// in a consistent and stable state when these callbacks are delivered, and to
// ensure that's the case, callbacks are not immediately delivered from where
// they originate, but instead queued (deferred) by this class. At the end of
// any public API method that may result in callbacks, they are triggered and
// then delivered.
//
// There are a number of exceptions, which is clearly annotated in the API.
class CallbackDeferrer : public DcSctpSocketCallbacks {
public:
explicit CallbackDeferrer(DcSctpSocketCallbacks& underlying)
: underlying_(underlying) {}
void TriggerDeferred() {
// Need to swap here. The client may call into the library from within a
// callback, and that might result in adding new callbacks to this instance,
// and the vector can't be modified while iterated on.
std::vector<std::function<void(DcSctpSocketCallbacks & cb)>> deferred;
deferred.swap(deferred_);
for (auto& cb : deferred) {
cb(underlying_);
}
}
void SendPacket(rtc::ArrayView<const uint8_t> data) override {
// Will not be deferred - call directly.
underlying_.SendPacket(data);
}
std::unique_ptr<Timeout> CreateTimeout() override {
// Will not be deferred - call directly.
return underlying_.CreateTimeout();
}
TimeMs TimeMillis() override {
// Will not be deferred - call directly.
return underlying_.TimeMillis();
}
uint32_t GetRandomInt(uint32_t low, uint32_t high) override {
// Will not be deferred - call directly.
return underlying_.GetRandomInt(low, high);
}
void OnMessageReceived(DcSctpMessage message) override {
deferred_.emplace_back(
[deliverer = MessageDeliverer(std::move(message))](
DcSctpSocketCallbacks& cb) mutable { deliverer.Deliver(cb); });
}
void OnError(ErrorKind error, absl::string_view message) override {
deferred_.emplace_back(
[error, message = std::string(message)](DcSctpSocketCallbacks& cb) {
cb.OnError(error, message);
});
}
void OnAborted(ErrorKind error, absl::string_view message) override {
deferred_.emplace_back(
[error, message = std::string(message)](DcSctpSocketCallbacks& cb) {
cb.OnAborted(error, message);
});
}
void OnConnected() override {
deferred_.emplace_back([](DcSctpSocketCallbacks& cb) { cb.OnConnected(); });
}
void OnClosed() override {
deferred_.emplace_back([](DcSctpSocketCallbacks& cb) { cb.OnClosed(); });
}
void OnConnectionRestarted() override {
deferred_.emplace_back(
[](DcSctpSocketCallbacks& cb) { cb.OnConnectionRestarted(); });
}
void OnStreamsResetFailed(rtc::ArrayView<const StreamID> outgoing_streams,
absl::string_view reason) override {
deferred_.emplace_back(
[streams = std::vector<StreamID>(outgoing_streams.begin(),
outgoing_streams.end()),
reason = std::string(reason)](DcSctpSocketCallbacks& cb) {
cb.OnStreamsResetFailed(streams, reason);
});
}
void OnStreamsResetPerformed(
rtc::ArrayView<const StreamID> outgoing_streams) override {
deferred_.emplace_back(
[streams = std::vector<StreamID>(outgoing_streams.begin(),
outgoing_streams.end())](
DcSctpSocketCallbacks& cb) {
cb.OnStreamsResetPerformed(streams);
});
}
void OnIncomingStreamsReset(
rtc::ArrayView<const StreamID> incoming_streams) override {
deferred_.emplace_back(
[streams = std::vector<StreamID>(incoming_streams.begin(),
incoming_streams.end())](
DcSctpSocketCallbacks& cb) { cb.OnIncomingStreamsReset(streams); });
}
void OnBufferedAmountLow(StreamID stream_id) override {
deferred_.emplace_back([stream_id](DcSctpSocketCallbacks& cb) {
cb.OnBufferedAmountLow(stream_id);
});
}
void OnTotalBufferedAmountLow() override {
deferred_.emplace_back(
[](DcSctpSocketCallbacks& cb) { cb.OnTotalBufferedAmountLow(); });
}
private:
// A wrapper around the move-only DcSctpMessage, to let it be captured in a
// lambda.
class MessageDeliverer {
public:
explicit MessageDeliverer(DcSctpMessage&& message)
: state_(rtc::make_ref_counted<State>(std::move(message))) {}
void Deliver(DcSctpSocketCallbacks& c) {
// Really ensure that it's only called once.
RTC_DCHECK(!state_->has_delivered);
state_->has_delivered = true;
c.OnMessageReceived(std::move(state_->message));
}
private:
struct State : public rtc::RefCountInterface {
explicit State(DcSctpMessage&& m)
: has_delivered(false), message(std::move(m)) {}
bool has_delivered;
DcSctpMessage message;
};
rtc::scoped_refptr<State> state_;
};
DcSctpSocketCallbacks& underlying_;
std::vector<std::function<void(DcSctpSocketCallbacks& cb)>> deferred_;
};
} // namespace dcsctp
#endif // NET_DCSCTP_SOCKET_CALLBACK_DEFERRER_H_
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