import win32security
import win32file
import win32event
import win32con
import win32api
import pywintypes
class WinBufferedReadFile(object):
verbose = False
def __init__(self, filename):
self._hfile = win32file.CreateFile(filename,
win32con.GENERIC_READ | win32con.GENERIC_WRITE,
win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE,
win32security.SECURITY_ATTRIBUTES(),
win32con.OPEN_EXISTING,
win32con.FILE_FLAG_OVERLAPPED,
0)
self._read_ovrlpd = pywintypes.OVERLAPPED()
self._read_ovrlpd.hEvent = win32event.CreateEvent(None, True,
False, None)
self._write_ovrlpd = pywintypes.OVERLAPPED()
self._write_ovrlpd.hEvent = win32event.CreateEvent(None, True,
False, None)
self._bufs = []
self._n = 0
def __del__(self):
win32api.CloseHandle(self._read_ovrlpd.hEvent)
win32api.CloseHandle(self._write_ovrlpd.hEvent)
def close(self):
win32api.CloseHandle(self._hfile)
def write(self, s):
win32file.WriteFile(self._hfile, s, self._write_ovrlpd)
win32file.GetOverlappedResult(self._hfile, self._write_ovrlpd, True)
def flush(self):
pass # TODO: flush in win32file?
def read(self, n):
while True: # emulate blocking IO
if self._n >= n:
frags = []
frags_length = 0
if self.verbose:
txt = "get %s, | bufs = %s " % (n, self._n)
txt += "[%s]" % ','.join(map(lambda x: str(len(x)),
self._bufs))
print(txt)
while frags_length < n:
frags.append(self._bufs.pop(0))
frags_length += len(frags[-1])
self._n -= n
whole = ''.join(frags)
ret = whole[:n]
rest = whole[n:]
if len(rest) > 0:
self._bufs.append(rest)
if self.verbose:
txt = "return %s(%s), | bufs = %s " % (len(ret), n,
self._n)
txt += "[%s]" % ','.join(map(lambda x: str(len(x)),
self._bufs))
print(txt)
return ret
try:
# 4096 is the largest result viosdev will return right now.
err, b = win32file.ReadFile(self._hfile, 4096,
self._read_ovrlpd)
nr = win32file.GetOverlappedResult(self._hfile,
self._read_ovrlpd,
True)
if nr > 0:
self._bufs.append(b[:nr])
self._n += nr
if self.verbose:
txt = "read %s, err %s | bufs = %s " % (nr, err, self._n)
txt += "[%s]" % ','.join(map(lambda x: str(len(x)),
self._bufs))
print(txt)
except Exception:
pass
# Never Reached
raise Exception("Error in WinBufferedReadFile - should never be reached")
