Function sendfile

src/windows/libwinio.cpp:702–741

Future<size_t> sendfile(
    const int_fd& socket, const int_fd& file, off_t offset, size_t size)
{
  process::initialize();

  if (offset < 0) {
    return Failure("process::windows::sendfile got negative offset");
  }

  Promise<size_t>* promise = new Promise<size_t>();
  Future<size_t> future = promise->future();

  auto overlapped = std::make_shared<IOOverlappedReadWrite>(
      IOOverlappedBase{OVERLAPPED{}, socket, IOType::SENDFILE}, promise);

  uint64_t offset64 = static_cast<uint64_t>(offset);
  overlapped->base.overlapped.Offset = static_cast<DWORD>(offset64);
  overlapped->base.overlapped.OffsetHigh = static_cast<DWORD>(offset64 >> 32);

  enable_cancellation(socket, future, overlapped);

  const Result<size_t> result =
    os::sendfile_async(socket, file, size, &overlapped->base.overlapped);

  // If the request is pending, then we return immediately and have the
  // callback free the promise and overlapped.
  if (result.isNone()) {
    return future;
  }

  // In an error or immediate success, we have to manually set the promise
  // and free it.
  if (result.isError()) {
    promise->fail("os::sendfile_async failed: " + result.error());
  } else if (result.isSome()) {
    promise->set(result.get());
  }
  delete promise;
  return future;
}

} // namespace windows {
} // namespace process {