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|
import os
import sys
from . import exceptions
from . import constants
if os.name == 'nt': # pragma: no cover
import win32con
import win32file
import pywintypes
import winerror
import msvcrt
__overlapped = pywintypes.OVERLAPPED()
if sys.version_info.major == 2:
lock_length = -1
else:
lock_length = int(2**31 - 1)
def lock(file_, flags):
if flags & constants.LOCK_SH:
if sys.version_info.major == 2:
if flags & constants.LOCK_NB:
mode = win32con.LOCKFILE_FAIL_IMMEDIATELY
else:
mode = 0
else:
if flags & constants.LOCK_NB:
mode = msvcrt.LK_NBRLCK
else:
mode = msvcrt.LK_RLCK
# is there any reason not to reuse the following structure?
hfile = win32file._get_osfhandle(file_.fileno())
try:
win32file.LockFileEx(hfile, mode, 0, -0x10000, __overlapped)
except pywintypes.error as exc_value:
# error: (33, 'LockFileEx', 'The process cannot access the file
# because another process has locked a portion of the file.')
if exc_value.winerror == winerror.ERROR_LOCK_VIOLATION:
raise exceptions.LockException(
exceptions.LockException.LOCK_FAILED,
exc_value.strerror,
fh=file_)
else:
# Q: Are there exceptions/codes we should be dealing with
# here?
raise
else:
mode = win32con.LOCKFILE_EXCLUSIVE_LOCK
if flags & constants.LOCK_NB:
mode |= win32con.LOCKFILE_FAIL_IMMEDIATELY
if flags & constants.LOCK_NB:
mode = msvcrt.LK_NBLCK
else:
mode = msvcrt.LK_LOCK
# windows locks byte ranges, so make sure to lock from file start
try:
savepos = file_.tell()
if savepos:
# [ ] test exclusive lock fails on seek here
# [ ] test if shared lock passes this point
file_.seek(0)
# [x] check if 0 param locks entire file (not documented in
# Python)
# [x] fails with "IOError: [Errno 13] Permission denied",
# but -1 seems to do the trick
try:
msvcrt.locking(file_.fileno(), mode, lock_length)
except IOError as exc_value:
# [ ] be more specific here
raise exceptions.LockException(
exceptions.LockException.LOCK_FAILED,
exc_value.strerror,
fh=file_)
finally:
if savepos:
file_.seek(savepos)
except IOError as exc_value:
raise exceptions.LockException(
exceptions.LockException.LOCK_FAILED, exc_value.strerror,
fh=file_)
def unlock(file_):
try:
savepos = file_.tell()
if savepos:
file_.seek(0)
try:
msvcrt.locking(file_.fileno(), constants.LOCK_UN, lock_length)
except IOError as exc_value:
if exc_value.strerror == 'Permission denied':
hfile = win32file._get_osfhandle(file_.fileno())
try:
win32file.UnlockFileEx(
hfile, 0, -0x10000, __overlapped)
except pywintypes.error as exc_value:
if exc_value.winerror == winerror.ERROR_NOT_LOCKED:
# error: (158, 'UnlockFileEx',
# 'The segment is already unlocked.')
# To match the 'posix' implementation, silently
# ignore this error
pass
else:
# Q: Are there exceptions/codes we should be
# dealing with here?
raise
else:
raise exceptions.LockException(
exceptions.LockException.LOCK_FAILED,
exc_value.strerror,
fh=file_)
finally:
if savepos:
file_.seek(savepos)
except IOError as exc_value:
raise exceptions.LockException(
exceptions.LockException.LOCK_FAILED, exc_value.strerror,
fh=file_)
elif os.name == 'posix': # pragma: no cover
import fcntl
def lock(file_, flags):
locking_exceptions = IOError,
try: # pragma: no cover
locking_exceptions += BlockingIOError,
except NameError: # pragma: no cover
pass
try:
fcntl.flock(file_.fileno(), flags)
except locking_exceptions as exc_value:
# The exception code varies on different systems so we'll catch
# every IO error
raise exceptions.LockException(exc_value, fh=file_)
def unlock(file_):
fcntl.flock(file_.fileno(), constants.LOCK_UN)
else: # pragma: no cover
raise RuntimeError('PortaLocker only defined for nt and posix platforms')
|
