traditional_reassembly_streams.h

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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_RX_TRADITIONAL_REASSEMBLY_STREAMS_H_

#define NET_DCSCTP_RX_TRADITIONAL_REASSEMBLY_STREAMS_H_

#include <stddef.h>

#include <stdint.h>

#include <map>

#include <string>

#include "absl/strings/string_view.h"

#include "api/array_view.h"

#include "net/dcsctp/common/sequence_numbers.h"

#include "net/dcsctp/packet/chunk/forward_tsn_common.h"

#include "net/dcsctp/packet/data.h"

#include "net/dcsctp/rx/reassembly_streams.h"

namespace dcsctp {

// Handles reassembly of incoming data when interleaved message sending

// is not enabled on the association, i.e. when RFC8260 is not in use and

// RFC4960 is to be followed.

class TraditionalReassemblyStreams : public ReassemblyStreams {

 public:

  TraditionalReassemblyStreams(absl::string_view log_prefix,

                               OnAssembledMessage on_assembled_message);

  int Add(UnwrappedTSN tsn, Data data) override;

  size_t HandleForwardTsn(

      UnwrappedTSN new_cumulative_ack_tsn,

      rtc::ArrayView<const AnyForwardTsnChunk::SkippedStream> skipped_streams)

      override;

  void ResetStreams(rtc::ArrayView<const StreamID> stream_ids) override;

  HandoverReadinessStatus GetHandoverReadiness() const override;

  void AddHandoverState(DcSctpSocketHandoverState& state) override;

  void RestoreFromState(const DcSctpSocketHandoverState& state) override;

 private:

  using ChunkMap = std::map<UnwrappedTSN, Data>;

  // Base class for `UnorderedStream` and `OrderedStream`.

  class StreamBase {

   protected:

    explicit StreamBase(TraditionalReassemblyStreams* parent)

        : parent_(*parent) {}

    size_t AssembleMessage(ChunkMap::iterator start, ChunkMap::iterator end);

    size_t AssembleMessage(UnwrappedTSN tsn, Data data);

    TraditionalReassemblyStreams& parent_;

};

  // Manages all received data for a specific unordered stream, and assembles

  // messages when possible.

  class UnorderedStream : StreamBase {

   public:

    explicit UnorderedStream(TraditionalReassemblyStreams* parent)

        : StreamBase(parent) {}

    int Add(UnwrappedTSN tsn, Data data);

    // Returns the number of bytes removed from the queue.

    size_t EraseTo(UnwrappedTSN tsn);

    bool has_unassembled_chunks() const { return !chunks_.empty(); }

   private:

    // Given an iterator to any chunk within the map, try to assemble a message

    // into `reassembled_messages` containing it and - if successful - erase

    // those chunks from the stream chunks map.

//

    // Returns the number of bytes that were assembled.

    size_t TryToAssembleMessage(ChunkMap::iterator iter);

    ChunkMap chunks_;

};

  // Manages all received data for a specific ordered stream, and assembles

  // messages when possible.

  class OrderedStream : StreamBase {

   public:

    explicit OrderedStream(TraditionalReassemblyStreams* parent,

                           SSN next_ssn = SSN(0))

        : StreamBase(parent), next_ssn_(ssn_unwrapper_.Unwrap(next_ssn)) {}

    int Add(UnwrappedTSN tsn, Data data);

    size_t EraseTo(SSN ssn);

    void Reset() {

      ssn_unwrapper_.Reset();

      next_ssn_ = ssn_unwrapper_.Unwrap(SSN(0));

    SSN next_ssn() const { return next_ssn_.Wrap(); }

    bool has_unassembled_chunks() const { return !chunks_by_ssn_.empty(); }

   private:

    // Try to assemble one or several messages in order from the stream.

    // Returns the number of bytes assembled if a message was assembled.

    size_t TryToAssembleMessage();

    size_t TryToAssembleMessages();

    // Same as above but when inserting the first complete message avoid

    // insertion into the map.

    size_t TryToAssembleMessagesFastpath(UnwrappedSSN ssn,

                                         UnwrappedTSN tsn,

                                         Data data);

    // This must be an ordered container to be able to iterate in SSN order.

    std::map<UnwrappedSSN, ChunkMap> chunks_by_ssn_;

    UnwrappedSSN::Unwrapper ssn_unwrapper_;

    UnwrappedSSN next_ssn_;

};

  const absl::string_view log_prefix_;

  // Callback for when a message has been assembled.

  const OnAssembledMessage on_assembled_message_;

  // All unordered and ordered streams, managing not-yet-assembled data.

  std::map<StreamID, UnorderedStream> unordered_streams_;

  std::map<StreamID, OrderedStream> ordered_streams_;

};

}  // namespace dcsctp

#endif  // NET_DCSCTP_RX_TRADITIONAL_REASSEMBLY_STREAMS_H_