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106 lines
3.5 KiB
Python
106 lines
3.5 KiB
Python
9 years ago
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# -*- coding: utf-8 -*-
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r"""
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werkzeug.posixemulation
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~~~~~~~~~~~~~~~~~~~~~~~
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Provides a POSIX emulation for some features that are relevant to
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web applications. The main purpose is to simplify support for
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systems such as Windows NT that are not 100% POSIX compatible.
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Currently this only implements a :func:`rename` function that
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follows POSIX semantics. Eg: if the target file already exists it
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will be replaced without asking.
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This module was introduced in 0.6.1 and is not a public interface.
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It might become one in later versions of Werkzeug.
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:copyright: (c) 2013 by the Werkzeug Team, see AUTHORS for more details.
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:license: BSD, see LICENSE for more details.
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"""
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import sys
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import os
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import errno
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import time
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import random
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can_rename_open_file = False
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if os.name == 'nt': # pragma: no cover
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_rename = lambda src, dst: False
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_rename_atomic = lambda src, dst: False
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try:
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import ctypes
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_MOVEFILE_REPLACE_EXISTING = 0x1
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_MOVEFILE_WRITE_THROUGH = 0x8
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_MoveFileEx = ctypes.windll.kernel32.MoveFileExW
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def _rename(src, dst):
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if not isinstance(src, unicode):
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src = unicode(src, sys.getfilesystemencoding())
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if not isinstance(dst, unicode):
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dst = unicode(dst, sys.getfilesystemencoding())
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if _rename_atomic(src, dst):
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return True
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retry = 0
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rv = False
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while not rv and retry < 100:
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rv = _MoveFileEx(src, dst, _MOVEFILE_REPLACE_EXISTING |
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_MOVEFILE_WRITE_THROUGH)
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if not rv:
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time.sleep(0.001)
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retry += 1
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return rv
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# new in Vista and Windows Server 2008
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_CreateTransaction = ctypes.windll.ktmw32.CreateTransaction
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_CommitTransaction = ctypes.windll.ktmw32.CommitTransaction
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_MoveFileTransacted = ctypes.windll.kernel32.MoveFileTransactedW
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_CloseHandle = ctypes.windll.kernel32.CloseHandle
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can_rename_open_file = True
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def _rename_atomic(src, dst):
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ta = _CreateTransaction(None, 0, 0, 0, 0, 1000, 'Werkzeug rename')
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if ta == -1:
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return False
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try:
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retry = 0
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rv = False
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while not rv and retry < 100:
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rv = _MoveFileTransacted(src, dst, None, None,
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_MOVEFILE_REPLACE_EXISTING |
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_MOVEFILE_WRITE_THROUGH, ta)
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if rv:
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rv = _CommitTransaction(ta)
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break
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else:
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time.sleep(0.001)
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retry += 1
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return rv
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finally:
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_CloseHandle(ta)
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except Exception:
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pass
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def rename(src, dst):
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# Try atomic or pseudo-atomic rename
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if _rename(src, dst):
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return
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# Fall back to "move away and replace"
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try:
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os.rename(src, dst)
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except OSError as e:
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if e.errno != errno.EEXIST:
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raise
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old = "%s-%08x" % (dst, random.randint(0, sys.maxint))
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os.rename(dst, old)
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os.rename(src, dst)
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try:
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os.unlink(old)
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except Exception:
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pass
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else:
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rename = os.rename
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can_rename_open_file = True
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