Win32SerialParityCheckStream.h

Enable keyboard shortcuts

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_dom_Win32SerialParityCheckStream_h

#define mozilla_dom_Win32SerialParityCheckStream_h

#include "mozilla/UniquePtrExtensions.h"

#include "nsCOMPtr.h"

#include "nsIAsyncInputStream.h"

namespace mozilla::dom {

// Wraps the raw serial read stream on Windows when parity checking is enabled.

// Windows does not mark parity errors inline in the byte stream; instead the

// driver records them and they are reported by IOCTL_SERIAL_GET_COMMSTATUS

// (the IOCTL behind ClearCommError()). This stream delegates reads to the inner

// stream and, after each read, polls that IOCTL for SERIAL_ERROR_PARITY. On

// detecting a parity error it delivers the bytes from the current read and

// then fails its next read with NS_ERROR_DOM_SERIAL_PARITY_ERROR, which rides

// the DataPipe close channel to the content process to surface a "ParityError"

// DOMException.

class Win32SerialParityCheckStream final : public nsIAsyncInputStream {

 public:

  NS_DECL_THREADSAFE_ISUPPORTS

  NS_DECL_NSIINPUTSTREAM

  NS_DECL_NSIASYNCINPUTSTREAM

  Win32SerialParityCheckStream(nsCOMPtr<nsIAsyncInputStream> aInner,

                               UniqueFileHandle aCommHandle);

 private:

  ~Win32SerialParityCheckStream() = default;

  // Polls the comm status and latches a parity error if one is reported.

  void CheckForParityError();

  nsCOMPtr<nsIAsyncInputStream> mInner;

  // A duplicate of the comm port handle, used solely for comm status polling.

  UniqueFileHandle mCommHandle;

  // Set once a parity error has been observed. After the bytes from the read

  // that observed it are delivered, the next read fails with the parity error.

  bool mParityErrorLatched = false;

};

}  // namespace mozilla::dom

#endif  // mozilla_dom_Win32SerialParityCheckStream_h