mvfst/quic/codec/QuicPacketRebuilder.h

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

#pragma once

#include <quic/codec/QuicPacketBuilder.h>
#include <quic/state/StateData.h>

namespace quic {

/**
 * A PacketRebuilder is a packet builder that takes in a list of frames, and
 * pass them onto a wrapped builder to rebuild the packet. Note that you still
 * buildPacket() from the wrapped in builder.
 * TODO: The cloning builder only clones stream data that has not already been
 * reset or closed. It is possible that a packet may have contained data for
 * only closed streams. In that case we would only write out the header.
 * This is a waste, so we should do something about this in the future.
 */
class PacketRebuilder {
 public:
  PacketRebuilder(
      PacketBuilderInterface& regularBuilder,
      QuicConnectionStateBase& conn);

  [[nodiscard]] quic::Expected<Optional<ClonedPacketIdentifier>, QuicError>
  rebuildFromPacket(OutstandingPacketWrapper& packet);

  // TODO: Same as passing cipherOverhead into the CloningScheduler, this really
  // is a sad way to solve the writableBytes problem.
  uint64_t getHeaderBytes() const;

 private:
  /**
   * A helper function that takes a OutstandingPacketWrapper that's not
   * processed, and return its maybeClonedPacketIdentifier. If this packet has
   * never been cloned, then create the maybeClonedPacketIdentifier and add it
   * into outstandings.clonedPacketIdentifiers first.
   */
  ClonedPacketIdentifier cloneOutstandingPacket(
      OutstandingPacketWrapper& packet);

  bool retransmittable(const QuicStreamState& stream) const {
    return stream.sendState == StreamSendState::Open;
  }

  const ChainedByteRangeHead* cloneCryptoRetransmissionBuffer(
      const WriteCryptoFrame& frame,
      const QuicCryptoStream& stream);

  const ChainedByteRangeHead* cloneRetransmissionBuffer(
      const WriteStreamFrame& frame,
      const QuicStreamState* stream);

 private:
  PacketBuilderInterface& builder_;
  QuicConnectionStateBase& conn_;
};
} // namespace quic