Win32Serial.read coding error for non-blocking read

[tmtopka]

BPO	11080
Nosy	@briancurtin
Files	serialwin32.py: Package pyserial driver for 32-bit Windows platform

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2011-01-31.16:59:52.662>
created_at = <Date 2011-01-31.16:58:55.236>
labels = ['extension-modules', 'invalid', 'OS-windows', 'type-crash']
title = 'Win32Serial.read coding error for non-blocking read'
updated_at = <Date 2011-01-31.16:59:52.661>
user = 'https://bugs.python.org/tmtopka'

bugs.python.org fields:

activity = <Date 2011-01-31.16:59:52.661>
actor = 'brian.curtin'
assignee = 'none'
closed = True
closed_date = <Date 2011-01-31.16:59:52.662>
closer = 'brian.curtin'
components = ['Extension Modules', 'Windows']
creation = <Date 2011-01-31.16:58:55.236>
creator = 'tmtopka'
dependencies = []
files = ['20628']
hgrepos = []
issue_num = 11080
keywords = []
message_count = 2.0
messages = ['127619', '127620']
nosy_count = 2.0
nosy_names = ['brian.curtin', 'tmtopka']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue11080'
versions = ['Python 2.6', '3rd party']

[tmtopka]

Attempting to read a fixed amount of data when the serial port is configured for non-blocking reads (i.e. self.timeout == 0) will occasionally throw an invalid memory access exception, due to an error in the following code:

### pyserial-2.5-rc2 serialWin32.py Line 219
            if self.timeout == 0:
                n = min(comstat.cbInQue, size)
                if n > 0:
                    buf = ctypes.create_string_buffer(n)
                    rc = win32.DWORD()
                    err = win32.ReadFile(self.hComPort, buf, size, ctypes.byref(rc), ctypes.byref(self._overlappedRead))

The buffer length passed to win32.ReadFile should be 'n', not 'size'. This may not have been noticed since it is timing dependent: only if additional input is enqueued inbetween accessing the input queue length and the ReadFile call will the inappropriate invalid memory access exception be raised when 'size' is greater than 'n'.

[briancurtin]

You should contact pyserial.