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EDITING: serialwin32.py

#! python
#
# backend for Windows ("win32" incl. 32/64 bit support)
#
# (C) 2001-2015 Chris Liechti <cliechti@gmx.net>
#
# This file is part of pySerial. https://github.com/pyserial/pyserial
# SPDX-License-Identifier:    BSD-3-Clause
#
# Initial patch to use ctypes by Giovanni Bajo <rasky@develer.com>

# pylint: disable=invalid-name,too-few-public-methods
import ctypes
import time
from serial import win32

import serial
from serial.serialutil import SerialBase, SerialException, to_bytes, portNotOpenError, writeTimeoutError

class Serial(SerialBase):
    """Serial port implementation for Win32 based on ctypes."""

BAUDRATES = (50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800,
                 9600, 19200, 38400, 57600, 115200)

def __init__(self, *args, **kwargs):
        self._port_handle = None
        self._overlapped_read = None
        self._overlapped_write = None
        super(Serial, self).__init__(*args, **kwargs)

def open(self):
        """\
        Open port with current settings. This may throw a SerialException
        if the port cannot be opened.
        """
        if self._port is None:
            raise SerialException("Port must be configured before it can be used.")
        if self.is_open:
            raise SerialException("Port is already open.")
        # the "\\.\COMx" format is required for devices other than COM1-COM8
        # not all versions of windows seem to support this properly
        # so that the first few ports are used with the DOS device name
        port = self.name
        try:
            if port.upper().startswith('COM') and int(port[3:]) > 8:
                port = '\\\\.\\' + port
        except ValueError:
            # for like COMnotanumber
            pass
        self._port_handle = win32.CreateFile(
            port,
            win32.GENERIC_READ | win32.GENERIC_WRITE,
            0,  # exclusive access
            None,  # no security
            win32.OPEN_EXISTING,
            win32.FILE_ATTRIBUTE_NORMAL | win32.FILE_FLAG_OVERLAPPED,
            0)
        if self._port_handle == win32.INVALID_HANDLE_VALUE:
            self._port_handle = None    # 'cause __del__ is called anyway
            raise SerialException("could not open port {!r}: {!r}".format(self.portstr, ctypes.WinError()))

try:
            self._overlapped_read = win32.OVERLAPPED()
            self._overlapped_read.hEvent = win32.CreateEvent(None, 1, 0, None)
            self._overlapped_write = win32.OVERLAPPED()
            #~ self._overlapped_write.hEvent = win32.CreateEvent(None, 1, 0, None)
            self._overlapped_write.hEvent = win32.CreateEvent(None, 0, 0, None)

# Setup a 4k buffer
            win32.SetupComm(self._port_handle, 4096, 4096)

# Save original timeout values:
            self._orgTimeouts = win32.COMMTIMEOUTS()
            win32.GetCommTimeouts(self._port_handle, ctypes.byref(self._orgTimeouts))

self._reconfigure_port()

# Clear buffers:
            # Remove anything that was there
            win32.PurgeComm(
                self._port_handle,
                win32.PURGE_TXCLEAR | win32.PURGE_TXABORT |
                win32.PURGE_RXCLEAR | win32.PURGE_RXABORT)
        except:
            try:
                self._close()
            except:
                # ignore any exception when closing the port
                # also to keep original exception that happened when setting up
                pass
            self._port_handle = None
            raise
        else:
            self.is_open = True

def _reconfigure_port(self):
        """Set communication parameters on opened port."""
        if not self._port_handle:
            raise SerialException("Can only operate on a valid port handle")

# Set Windows timeout values
        # timeouts is a tuple with the following items:
        # (ReadIntervalTimeout,ReadTotalTimeoutMultiplier,
        #  ReadTotalTimeoutConstant,WriteTotalTimeoutMultiplier,
        #  WriteTotalTimeoutConstant)
        timeouts = win32.COMMTIMEOUTS()
        if self._timeout is None:
            pass  # default of all zeros is OK
        elif self._timeout == 0:
            timeouts.ReadIntervalTimeout = win32.MAXDWORD
        else:
            timeouts.ReadTotalTimeoutConstant = max(int(self._timeout * 1000), 1)
        if self._timeout != 0 and self._inter_byte_timeout is not None:
            timeouts.ReadIntervalTimeout = max(int(self._inter_byte_timeout * 1000), 1)

if self._write_timeout is None:
            pass
        elif self._write_timeout == 0:
            timeouts.WriteTotalTimeoutConstant = win32.MAXDWORD
        else:
            timeouts.WriteTotalTimeoutConstant = max(int(self._write_timeout * 1000), 1)
        win32.SetCommTimeouts(self._port_handle, ctypes.byref(timeouts))

win32.SetCommMask(self._port_handle, win32.EV_ERR)

# Setup the connection info.
        # Get state and modify it:
        comDCB = win32.DCB()
        win32.GetCommState(self._port_handle, ctypes.byref(comDCB))
        comDCB.BaudRate = self._baudrate

if self._bytesize == serial.FIVEBITS:
            comDCB.ByteSize = 5
        elif self._bytesize == serial.SIXBITS:
            comDCB.ByteSize = 6
        elif self._bytesize == serial.SEVENBITS:
            comDCB.ByteSize = 7
        elif self._bytesize == serial.EIGHTBITS:
            comDCB.ByteSize = 8
        else:
            raise ValueError("Unsupported number of data bits: {!r}".format(self._bytesize))

if self._parity == serial.PARITY_NONE:
            comDCB.Parity = win32.NOPARITY
            comDCB.fParity = 0  # Disable Parity Check
        elif self._parity == serial.PARITY_EVEN:
            comDCB.Parity = win32.EVENPARITY
            comDCB.fParity = 1  # Enable Parity Check
        elif self._parity == serial.PARITY_ODD:
            comDCB.Parity = win32.ODDPARITY
            comDCB.fParity = 1  # Enable Parity Check
        elif self._parity == serial.PARITY_MARK:
            comDCB.Parity = win32.MARKPARITY
            comDCB.fParity = 1  # Enable Parity Check
        elif self._parity == serial.PARITY_SPACE:
            comDCB.Parity = win32.SPACEPARITY
            comDCB.fParity = 1  # Enable Parity Check
        else:
            raise ValueError("Unsupported parity mode: {!r}".format(self._parity))

if self._stopbits == serial.STOPBITS_ONE:
            comDCB.StopBits = win32.ONESTOPBIT
        elif self._stopbits == serial.STOPBITS_ONE_POINT_FIVE:
            comDCB.StopBits = win32.ONE5STOPBITS
        elif self._stopbits == serial.STOPBITS_TWO:
            comDCB.StopBits = win32.TWOSTOPBITS
        else:
            raise ValueError("Unsupported number of stop bits: {!r}".format(self._stopbits))

comDCB.fBinary = 1  # Enable Binary Transmission
        # Char. w/ Parity-Err are replaced with 0xff (if fErrorChar is set to TRUE)
        if self._rs485_mode is None:
            if self._rtscts:
                comDCB.fRtsControl = win32.RTS_CONTROL_HANDSHAKE
            else:
                comDCB.fRtsControl = win32.RTS_CONTROL_ENABLE if self._rts_state else win32.RTS_CONTROL_DISABLE
            comDCB.fOutxCtsFlow = self._rtscts
        else:
            # checks for unsupported settings
            # XXX verify if platform really does not have a setting for those
            if not self._rs485_mode.rts_level_for_tx:
                raise ValueError(
                    'Unsupported value for RS485Settings.rts_level_for_tx: {!r}'.format(
                        self._rs485_mode.rts_level_for_tx,))
            if self._rs485_mode.rts_level_for_rx:
                raise ValueError(
                    'Unsupported value for RS485Settings.rts_level_for_rx: {!r}'.format(
                        self._rs485_mode.rts_level_for_rx,))
            if self._rs485_mode.delay_before_tx is not None:
                raise ValueError(
                    'Unsupported value for RS485Settings.delay_before_tx: {!r}'.format(
                        self._rs485_mode.delay_before_tx,))
            if self._rs485_mode.delay_before_rx is not None:
                raise ValueError(
                    'Unsupported value for RS485Settings.delay_before_rx: {!r}'.format(
                        self._rs485_mode.delay_before_rx,))
            if self._rs485_mode.loopback:
                raise ValueError(
                    'Unsupported value for RS485Settings.loopback: {!r}'.format(
                        self._rs485_mode.loopback,))
            comDCB.fRtsControl = win32.RTS_CONTROL_TOGGLE
            comDCB.fOutxCtsFlow = 0

if self._dsrdtr:
            comDCB.fDtrControl = win32.DTR_CONTROL_HANDSHAKE
        else:
            comDCB.fDtrControl = win32.DTR_CONTROL_ENABLE if self._dtr_state else win32.DTR_CONTROL_DISABLE
        comDCB.fOutxDsrFlow = self._dsrdtr
        comDCB.fOutX = self._xonxoff
        comDCB.fInX = self._xonxoff
        comDCB.fNull = 0
        comDCB.fErrorChar = 0
        comDCB.fAbortOnError = 0
        comDCB.XonChar = serial.XON
        comDCB.XoffChar = serial.XOFF

if not win32.SetCommState(self._port_handle, ctypes.byref(comDCB)):
            raise SerialException(
                'Cannot configure port, something went wrong. '
                'Original message: {!r}'.format(ctypes.WinError()))

#~ def __del__(self):
        #~ self.close()

def _close(self):
        """internal close port helper"""
        if self._port_handle is not None:
            # Restore original timeout values:
            win32.SetCommTimeouts(self._port_handle, self._orgTimeouts)
            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
            win32.CloseHandle(self._port_handle)
            self._port_handle = None

def close(self):
        """Close port"""
        if self.is_open:
            self._close()
            self.is_open = False

#  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -

@property
    def in_waiting(self):
        """Return the number of bytes currently in the input buffer."""
        flags = win32.DWORD()
        comstat = win32.COMSTAT()
        if not win32.ClearCommError(self._port_handle, ctypes.byref(flags), ctypes.byref(comstat)):
            raise SerialException("ClearCommError failed ({!r})".format(ctypes.WinError()))
        return comstat.cbInQue

def read(self, size=1):
        """\
        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.
        """
        if not self.is_open:
            raise portNotOpenError
        if size > 0:
            win32.ResetEvent(self._overlapped_read.hEvent)
            flags = win32.DWORD()
            comstat = win32.COMSTAT()
            if not win32.ClearCommError(self._port_handle, ctypes.byref(flags), ctypes.byref(comstat)):
                raise SerialException("ClearCommError failed ({!r})".format(ctypes.WinError()))
            n = min(comstat.cbInQue, size) if self.timeout == 0 else size
            if n > 0:
                buf = ctypes.create_string_buffer(n)
                rc = win32.DWORD()
                read_ok = win32.ReadFile(
                    self._port_handle,
                    buf,
                    n,
                    ctypes.byref(rc),
                    ctypes.byref(self._overlapped_read))
                if not read_ok and win32.GetLastError() not in (win32.ERROR_SUCCESS, win32.ERROR_IO_PENDING):
                    raise SerialException("ReadFile failed ({!r})".format(ctypes.WinError()))
                result_ok = win32.GetOverlappedResult(
                    self._port_handle,
                    ctypes.byref(self._overlapped_read),
                    ctypes.byref(rc),
                    True)
                if not result_ok:
                    if win32.GetLastError() != win32.ERROR_OPERATION_ABORTED:
                        raise SerialException("GetOverlappedResult failed ({!r})".format(ctypes.WinError()))
                read = buf.raw[:rc.value]
            else:
                read = bytes()
        else:
            read = bytes()
        return bytes(read)

def write(self, data):
        """Output the given byte string over the serial port."""
        if not self.is_open:
            raise portNotOpenError
        #~ if not isinstance(data, (bytes, bytearray)):
            #~ raise TypeError('expected %s or bytearray, got %s' % (bytes, type(data)))
        # convert data (needed in case of memoryview instance: Py 3.1 io lib), ctypes doesn't like memoryview
        data = to_bytes(data)
        if data:
            #~ win32event.ResetEvent(self._overlapped_write.hEvent)
            n = win32.DWORD()
            success = win32.WriteFile(self._port_handle, data, len(data), ctypes.byref(n), self._overlapped_write)
            if self._write_timeout != 0:  # if blocking (None) or w/ write timeout (>0)
                if not success and win32.GetLastError() not in (win32.ERROR_SUCCESS, win32.ERROR_IO_PENDING):
                    raise SerialException("WriteFile failed ({!r})".format(ctypes.WinError()))

# Wait for the write to complete.
                #~ win32.WaitForSingleObject(self._overlapped_write.hEvent, win32.INFINITE)
                win32.GetOverlappedResult(self._port_handle, self._overlapped_write, ctypes.byref(n), True)
                if win32.GetLastError() == win32.ERROR_OPERATION_ABORTED:
                    return n.value  # canceled IO is no error
                if n.value != len(data):
                    raise writeTimeoutError
                return n.value
            else:
                errorcode = win32.ERROR_SUCCESS if success else win32.GetLastError()
                if errorcode in (win32.ERROR_INVALID_USER_BUFFER, win32.ERROR_NOT_ENOUGH_MEMORY,
                                 win32.ERROR_OPERATION_ABORTED):
                    return 0
                elif errorcode in (win32.ERROR_SUCCESS, win32.ERROR_IO_PENDING):
                    # no info on true length provided by OS function in async mode
                    return len(data)
                else:
                    raise SerialException("WriteFile failed ({!r})".format(ctypes.WinError()))
        else:
            return 0

def flush(self):
        """\
        Flush of file like objects. In this case, wait until all data
        is written.
        """
        while self.out_waiting:
            time.sleep(0.05)
        # XXX could also use WaitCommEvent with mask EV_TXEMPTY, but it would
        # require overlapped IO and it's also only possible to set a single mask
        # on the port---

def reset_input_buffer(self):
        """Clear input buffer, discarding all that is in the buffer."""
        if not self.is_open:
            raise portNotOpenError
        win32.PurgeComm(self._port_handle, win32.PURGE_RXCLEAR | win32.PURGE_RXABORT)

def reset_output_buffer(self):
        """\
        Clear output buffer, aborting the current output and discarding all
        that is in the buffer.
        """
        if not self.is_open:
            raise portNotOpenError
        win32.PurgeComm(self._port_handle, win32.PURGE_TXCLEAR | win32.PURGE_TXABORT)

def _update_break_state(self):
        """Set break: Controls TXD. When active, to transmitting is possible."""
        if not self.is_open:
            raise portNotOpenError
        if self._break_state:
            win32.SetCommBreak(self._port_handle)
        else:
            win32.ClearCommBreak(self._port_handle)

def _update_rts_state(self):
        """Set terminal status line: Request To Send"""
        if self._rts_state:
            win32.EscapeCommFunction(self._port_handle, win32.SETRTS)
        else:
            win32.EscapeCommFunction(self._port_handle, win32.CLRRTS)

def _update_dtr_state(self):
        """Set terminal status line: Data Terminal Ready"""
        if self._dtr_state:
            win32.EscapeCommFunction(self._port_handle, win32.SETDTR)
        else:
            win32.EscapeCommFunction(self._port_handle, win32.CLRDTR)

def _GetCommModemStatus(self):
        if not self.is_open:
            raise portNotOpenError
        stat = win32.DWORD()
        win32.GetCommModemStatus(self._port_handle, ctypes.byref(stat))
        return stat.value

@property
    def cts(self):
        """Read terminal status line: Clear To Send"""
        return win32.MS_CTS_ON & self._GetCommModemStatus() != 0

@property
    def dsr(self):
        """Read terminal status line: Data Set Ready"""
        return win32.MS_DSR_ON & self._GetCommModemStatus() != 0

@property
    def ri(self):
        """Read terminal status line: Ring Indicator"""
        return win32.MS_RING_ON & self._GetCommModemStatus() != 0

@property
    def cd(self):
        """Read terminal status line: Carrier Detect"""
        return win32.MS_RLSD_ON & self._GetCommModemStatus() != 0

# - - platform specific - - - -

def set_buffer_size(self, rx_size=4096, tx_size=None):
        """\
        Recommend a buffer size to the driver (device driver can ignore this
        value). Must be called before the port is opened.
        """
        if tx_size is None:
            tx_size = rx_size
        win32.SetupComm(self._port_handle, rx_size, tx_size)

def set_output_flow_control(self, enable=True):
        """\
        Manually control flow - when software flow control is enabled.
        This will do the same as if XON (true) or XOFF (false) are received
        from the other device and control the transmission accordingly.
        WARNING: this function is not portable to different platforms!
        """
        if not self.is_open:
            raise portNotOpenError
        if enable:
            win32.EscapeCommFunction(self._port_handle, win32.SETXON)
        else:
            win32.EscapeCommFunction(self._port_handle, win32.SETXOFF)

@property
    def out_waiting(self):
        """Return how many bytes the in the outgoing buffer"""
        flags = win32.DWORD()
        comstat = win32.COMSTAT()
        if not win32.ClearCommError(self._port_handle, ctypes.byref(flags), ctypes.byref(comstat)):
            raise SerialException("ClearCommError failed ({!r})".format(ctypes.WinError()))
        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() in (win32.ERROR_IO_PENDING, win32.ERROR_IO_INCOMPLETE):
            # 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)

@SerialBase.exclusive.setter
    def exclusive(self, exclusive):
        """Change the exclusive access setting."""
        if exclusive is not None and not exclusive:
            raise ValueError('win32 only supports exclusive access (not: {})'.format(exclusive))
        else:
            serial.SerialBase.exclusive.__set__(self, exclusive)

CANCEL

Name	Type	Size	Modified	Actions
↩ ..	DIR	—	—
📁 __pycache__/	DIR	—	2026-04-10 12:14
📁 threaded/	DIR	—	2026-04-10 12:14
📁 tools/	DIR	—	2026-04-10 12:14
📁 urlhandler/	DIR	—	2026-04-10 12:14
📄 __init__.py	PY	3.1 KB	2017-07-22 20:49	EDIT
📄 rfc2217.py	PY	58.1 KB	2017-05-03 16:33	EDIT
📄 rs485.py	PY	3.2 KB	2015-12-16 21:52	EDIT
📄 serialcli.py	PY	8.9 KB	2016-06-09 18:29	EDIT
📄 serialjava.py	PY	8.2 KB	2016-01-30 22:39	EDIT
📄 serialposix.py	PY	30.9 KB	2017-07-14 19:49	EDIT
📄 serialutil.py	PY	21.2 KB	2017-07-13 21:31	EDIT
📄 serialwin32.py	PY	19.6 KB	2017-03-06 21:38	EDIT
📄 win32.py	PY	10.6 KB	2016-09-17 14:24	EDIT