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Diffstat (limited to 'werkzeug/posixemulation.py')
-rw-r--r-- | werkzeug/posixemulation.py | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/werkzeug/posixemulation.py b/werkzeug/posixemulation.py new file mode 100644 index 0000000..42171b8 --- /dev/null +++ b/werkzeug/posixemulation.py @@ -0,0 +1,104 @@ +# -*- coding: utf-8 -*- +r""" + werkzeug.posixemulation + ~~~~~~~~~~~~~~~~~~~~~~~ + + Provides a POSIX emulation for some features that are relevant to + web applications. The main purpose is to simplify support for + systems such as Windows NT that are not 100% POSIX compatible. + + Currently this only implements a :func:`rename` function that + follows POSIX semantics. Eg: if the target file already exists it + will be replaced without asking. + + This module was introduced in 0.6.1 and is not a public interface. + It might become one in later versions of Werkzeug. + + :copyright: (c) 2010 by the Werkzeug Team, see AUTHORS for more details. + :license: BSD, see LICENSE for more details. +""" +import os +import errno +import time +import random + + +can_rename_open_file = False +if os.name == 'nt': # pragma: no cover + _rename = lambda src, dst: False + _rename_atomic = lambda src, dst: False + + try: + import ctypes + + _MOVEFILE_REPLACE_EXISTING = 0x1 + _MOVEFILE_WRITE_THROUGH = 0x8 + _MoveFileEx = ctypes.windll.kernel32.MoveFileExW + + def _rename(src, dst): + if not isinstance(src, unicode): + src = unicode(src, sys.getfilesystemencoding()) + if not isinstance(dst, unicode): + dst = unicode(dst, sys.getfilesystemencoding()) + if _rename_atomic(src, dst): + return True + retry = 0 + rv = False + while not rv and retry < 100: + rv = _MoveFileEx(src, dst, _MOVEFILE_REPLACE_EXISTING | + _MOVEFILE_WRITE_THROUGH) + if not rv: + time.sleep(0.001) + retry += 1 + return rv + + # new in Vista and Windows Server 2008 + _CreateTransaction = ctypes.windll.ktmw32.CreateTransaction + _CommitTransaction = ctypes.windll.ktmw32.CommitTransaction + _MoveFileTransacted = ctypes.windll.kernel32.MoveFileTransactedW + _CloseHandle = ctypes.windll.kernel32.CloseHandle + can_rename_open_file = True + + def _rename_atomic(src, dst): + ta = _CreateTransaction(None, 0, 0, 0, 0, 1000, 'Werkzeug rename') + if ta == -1: + return False + try: + retry = 0 + rv = False + while not rv and retry < 100: + rv = _MoveFileTransacted(src, dst, None, None, + _MOVEFILE_REPLACE_EXISTING | + _MOVEFILE_WRITE_THROUGH, ta) + if rv: + rv = _CommitTransaction(ta) + break + else: + time.sleep(0.001) + retry += 1 + return rv + finally: + _CloseHandle(ta) + except Exception: + pass + + def rename(src, dst): + # Try atomic or pseudo-atomic rename + if _rename(src, dst): + return + # Fall back to "move away and replace" + try: + os.rename(src, dst) + except OSError, e: + if e.errno != errno.EEXIST: + raise + old = "%s-%08x" % (dst, random.randint(0, sys.maxint)) + os.rename(dst, old) + os.rename(src, dst) + try: + os.unlink(old) + except Exception: + pass +else: + rename = os.rename + can_rename_open_file = True |