quiche/quic/core/quic_blocked_writer_list.cc

// Copyright (c) 2024 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "quiche/quic/core/quic_blocked_writer_list.h"

#include <utility>

#include "quiche/quic/platform/api/quic_bug_tracker.h"
#include "quiche/quic/platform/api/quic_flag_utils.h"

namespace quic {

void QuicBlockedWriterList::Add(QuicBlockedWriterInterface& blocked_writer) {
  if (!blocked_writer.IsWriterBlocked()) {
    // It is a programming error if this ever happens. When we are sure it is
    // not happening, replace it with a QUICHE_DCHECK.
    QUIC_BUG(quic_bug_12724_4)
        << "Tried to add writer into blocked list when it shouldn't be added";
    // Return without adding the connection to the blocked list, to avoid
    // infinite loops in OnCanWrite.
    return;
  }

  write_blocked_list_.insert(std::make_pair(&blocked_writer, true));
}

bool QuicBlockedWriterList::Empty() const {
  return write_blocked_list_.empty();
}

bool QuicBlockedWriterList::Remove(QuicBlockedWriterInterface& blocked_writer) {
  return write_blocked_list_.erase(&blocked_writer) != 0;
}

void QuicBlockedWriterList::OnWriterUnblocked() {
  // Move every blocked writer in |write_blocked_list_| to a temporary list.
  const size_t num_blocked_writers_before = write_blocked_list_.size();
  WriteBlockedList temp_list;
  temp_list.swap(write_blocked_list_);
  QUICHE_DCHECK(write_blocked_list_.empty());

  // Give each blocked writer a chance to write what they intended to write.
  // If they are blocked again, they will call |OnWriteBlocked| to add
  // themselves back into |write_blocked_list_|.
  while (!temp_list.empty()) {
    QuicBlockedWriterInterface* blocked_writer = temp_list.begin()->first;
    temp_list.erase(temp_list.begin());
    blocked_writer->OnBlockedWriterCanWrite();
  }
  const size_t num_blocked_writers_after = write_blocked_list_.size();
  if (num_blocked_writers_after != 0) {
    if (num_blocked_writers_before == num_blocked_writers_after) {
      QUIC_CODE_COUNT(quic_zero_progress_on_can_write);
    } else {
      QUIC_CODE_COUNT(quic_blocked_again_on_can_write);
    }
  }
}

}  // namespace quic