win32: add methods to cancel read/write operation, use in close, fixes #51
diff --git a/serial/serialwin32.py b/serial/serialwin32.py
index cb2fa0b..1611e21 100644
--- a/serial/serialwin32.py
+++ b/serial/serialwin32.py
@@ -234,12 +234,12 @@
if self._port_handle:
# Restore original timeout values:
win32.SetCommTimeouts(self._port_handle, self._orgTimeouts)
- # Close COM-Port:
- win32.CloseHandle(self._port_handle)
if self._overlapped_read is not None:
+ self.cancel_read()
win32.CloseHandle(self._overlapped_read.hEvent)
self._overlapped_read = None
if self._overlapped_write is not None:
+ self.cancel_write()
win32.CloseHandle(self._overlapped_write.hEvent)
self._overlapped_write = None
self._port_handle = None
@@ -265,7 +265,8 @@
"""\
Read size bytes from the serial port. If a timeout is set it may
return less characters as requested. With no timeout it will block
- until the requested number of bytes is read."""
+ until the requested number of bytes is read.
+ """
if not self.is_open:
raise portNotOpenError
if size > 0:
@@ -431,3 +432,25 @@
if not win32.ClearCommError(self._port_handle, ctypes.byref(flags), ctypes.byref(comstat)):
raise SerialException('call to ClearCommError failed')
return comstat.cbOutQue
+
+ def _cancel_overlapped_io(self, overlapped):
+ """Cancel a blocking read operation, may be called from other thread"""
+ # check if read operation is pending
+ rc = win32.DWORD()
+ err = win32.GetOverlappedResult(
+ self._port_handle,
+ ctypes.byref(overlapped),
+ ctypes.byref(rc),
+ False)
+ if not err and win32.GetLastError() == win32.ERROR_IO_PENDING:
+ # cancel, ignoring any errors (e.g. it may just have finished on its own)
+ win32.CancelIoEx(self._port_handle, overlapped)
+
+ def cancel_read(self):
+ """Cancel a blocking read operation, may be called from other thread"""
+ self._cancel_overlapped_io(self._overlapped_read)
+
+ def cancel_write(self):
+ """Cancel a blocking write operation, may be called from other thread"""
+ self._cancel_overlapped_io(self._overlapped_write)
+
diff --git a/serial/win32.py b/serial/win32.py
index 43caae1..cef5568 100644
--- a/serial/win32.py
+++ b/serial/win32.py
@@ -179,6 +179,10 @@
WaitForSingleObject.restype = DWORD
WaitForSingleObject.argtypes = [HANDLE, DWORD]
+CancelIoEx = _stdcall_libraries['kernel32'].CancelIoEx
+CancelIoEx.restype = BOOL
+CancelIoEx.argtypes = [HANDLE, LPOVERLAPPED]
+
ONESTOPBIT = 0 # Variable c_int
TWOSTOPBITS = 2 # Variable c_int
ONE5STOPBITS = 1