win32: allocate buffer of maximum length for GetVolumeInformation()

It's documented that "the maximum buffer size is MAX_PATH+1", which is
slightly larger than 256.

https://msdn.microsoft.com/en-us/library/windows/desktop/aa364993(v=vs.85).aspx

mercurial/win32.py

@@ -1,636 +1,638 b''
 # win32.py - utility functions that use win32 API
 #
 # Copyright 2005-2009 Matt Mackall <[e-mail]> and others
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import ctypes
+import ctypes.wintypes as wintypes
 import errno
 import msvcrt
 import os
 import random
 import subprocess
 
 from . import (
     encoding,
     pycompat,
 )
 
 _kernel32 = ctypes.windll.kernel32
 _advapi32 = ctypes.windll.advapi32
 _user32 = ctypes.windll.user32
 _crypt32 = ctypes.windll.crypt32
 
 _BOOL = ctypes.c_long
 _WORD = ctypes.c_ushort
 _DWORD = ctypes.c_ulong
 _UINT = ctypes.c_uint
 _LONG = ctypes.c_long
 _LPCSTR = _LPSTR = ctypes.c_char_p
 _HANDLE = ctypes.c_void_p
 _HWND = _HANDLE
 _PCCERT_CONTEXT = ctypes.c_void_p
+_MAX_PATH = wintypes.MAX_PATH
 
 _INVALID_HANDLE_VALUE = _HANDLE(-1).value
 
 # GetLastError
 _ERROR_SUCCESS = 0
 _ERROR_NO_MORE_FILES = 18
 _ERROR_INVALID_PARAMETER = 87
 _ERROR_BROKEN_PIPE = 109
 _ERROR_INSUFFICIENT_BUFFER = 122
 
 # WPARAM is defined as UINT_PTR (unsigned type)
 # LPARAM is defined as LONG_PTR (signed type)
 if ctypes.sizeof(ctypes.c_long) == ctypes.sizeof(ctypes.c_void_p):
     _WPARAM = ctypes.c_ulong
     _LPARAM = ctypes.c_long
 elif ctypes.sizeof(ctypes.c_longlong) == ctypes.sizeof(ctypes.c_void_p):
     _WPARAM = ctypes.c_ulonglong
     _LPARAM = ctypes.c_longlong
 
 class _FILETIME(ctypes.Structure):
     _fields_ = [('dwLowDateTime', _DWORD),
                 ('dwHighDateTime', _DWORD)]
 
 class _BY_HANDLE_FILE_INFORMATION(ctypes.Structure):
     _fields_ = [('dwFileAttributes', _DWORD),
                 ('ftCreationTime', _FILETIME),
                 ('ftLastAccessTime', _FILETIME),
                 ('ftLastWriteTime', _FILETIME),
                 ('dwVolumeSerialNumber', _DWORD),
                 ('nFileSizeHigh', _DWORD),
                 ('nFileSizeLow', _DWORD),
                 ('nNumberOfLinks', _DWORD),
                 ('nFileIndexHigh', _DWORD),
                 ('nFileIndexLow', _DWORD)]
 
 # CreateFile
 _FILE_SHARE_READ = 0x00000001
 _FILE_SHARE_WRITE = 0x00000002
 _FILE_SHARE_DELETE = 0x00000004
 
 _OPEN_EXISTING = 3
 
 _FILE_FLAG_BACKUP_SEMANTICS = 0x02000000
 
 # SetFileAttributes
 _FILE_ATTRIBUTE_NORMAL = 0x80
 _FILE_ATTRIBUTE_NOT_CONTENT_INDEXED = 0x2000
 
 # Process Security and Access Rights
 _PROCESS_QUERY_INFORMATION = 0x0400
 
 # GetExitCodeProcess
 _STILL_ACTIVE = 259
 
 class _STARTUPINFO(ctypes.Structure):
     _fields_ = [('cb', _DWORD),
                 ('lpReserved', _LPSTR),
                 ('lpDesktop', _LPSTR),
                 ('lpTitle', _LPSTR),
                 ('dwX', _DWORD),
                 ('dwY', _DWORD),
                 ('dwXSize', _DWORD),
                 ('dwYSize', _DWORD),
                 ('dwXCountChars', _DWORD),
                 ('dwYCountChars', _DWORD),
                 ('dwFillAttribute', _DWORD),
                 ('dwFlags', _DWORD),
                 ('wShowWindow', _WORD),
                 ('cbReserved2', _WORD),
                 ('lpReserved2', ctypes.c_char_p),
                 ('hStdInput', _HANDLE),
                 ('hStdOutput', _HANDLE),
                 ('hStdError', _HANDLE)]
 
 class _PROCESS_INFORMATION(ctypes.Structure):
     _fields_ = [('hProcess', _HANDLE),
                 ('hThread', _HANDLE),
                 ('dwProcessId', _DWORD),
                 ('dwThreadId', _DWORD)]
 
 _CREATE_NO_WINDOW = 0x08000000
 _SW_HIDE = 0
 
 class _COORD(ctypes.Structure):
     _fields_ = [('X', ctypes.c_short),
                 ('Y', ctypes.c_short)]
 
 class _SMALL_RECT(ctypes.Structure):
     _fields_ = [('Left', ctypes.c_short),
                 ('Top', ctypes.c_short),
                 ('Right', ctypes.c_short),
                 ('Bottom', ctypes.c_short)]
 
 class _CONSOLE_SCREEN_BUFFER_INFO(ctypes.Structure):
     _fields_ = [('dwSize', _COORD),
                 ('dwCursorPosition', _COORD),
                 ('wAttributes', _WORD),
                 ('srWindow', _SMALL_RECT),
                 ('dwMaximumWindowSize', _COORD)]
 
 _STD_OUTPUT_HANDLE = _DWORD(-11).value
 _STD_ERROR_HANDLE = _DWORD(-12).value
 
 # CERT_TRUST_STATUS dwErrorStatus
 CERT_TRUST_IS_PARTIAL_CHAIN = 0x10000
 
 # CertCreateCertificateContext encodings
 X509_ASN_ENCODING = 0x00000001
 PKCS_7_ASN_ENCODING = 0x00010000
 
 # These structs are only complete enough to achieve what we need.
 class CERT_CHAIN_CONTEXT(ctypes.Structure):
     _fields_ = (
         ("cbSize", _DWORD),
 
         # CERT_TRUST_STATUS struct
         ("dwErrorStatus", _DWORD),
         ("dwInfoStatus", _DWORD),
 
         ("cChain", _DWORD),
         ("rgpChain", ctypes.c_void_p),
         ("cLowerQualityChainContext", _DWORD),
         ("rgpLowerQualityChainContext", ctypes.c_void_p),
         ("fHasRevocationFreshnessTime", _BOOL),
         ("dwRevocationFreshnessTime", _DWORD),
     )
 
 class CERT_USAGE_MATCH(ctypes.Structure):
     _fields_ = (
         ("dwType", _DWORD),
 
          # CERT_ENHKEY_USAGE struct
         ("cUsageIdentifier", _DWORD),
         ("rgpszUsageIdentifier", ctypes.c_void_p), # LPSTR *
     )
 
 class CERT_CHAIN_PARA(ctypes.Structure):
     _fields_ = (
         ("cbSize", _DWORD),
         ("RequestedUsage", CERT_USAGE_MATCH),
         ("RequestedIssuancePolicy", CERT_USAGE_MATCH),
         ("dwUrlRetrievalTimeout", _DWORD),
         ("fCheckRevocationFreshnessTime", _BOOL),
         ("dwRevocationFreshnessTime", _DWORD),
         ("pftCacheResync", ctypes.c_void_p), # LPFILETIME
         ("pStrongSignPara", ctypes.c_void_p), # PCCERT_STRONG_SIGN_PARA
         ("dwStrongSignFlags", _DWORD),
     )
 
 # types of parameters of C functions used (required by pypy)
 
 _crypt32.CertCreateCertificateContext.argtypes = [_DWORD, # cert encoding
                                                   ctypes.c_char_p, # cert
                                                   _DWORD] # cert size
 _crypt32.CertCreateCertificateContext.restype = _PCCERT_CONTEXT
 
 _crypt32.CertGetCertificateChain.argtypes = [
         ctypes.c_void_p, # HCERTCHAINENGINE
         _PCCERT_CONTEXT,
         ctypes.c_void_p, # LPFILETIME
         ctypes.c_void_p, # HCERTSTORE
         ctypes.c_void_p, # PCERT_CHAIN_PARA
         _DWORD,
         ctypes.c_void_p, # LPVOID
         ctypes.c_void_p  # PCCERT_CHAIN_CONTEXT *
     ]
 _crypt32.CertGetCertificateChain.restype = _BOOL
 
 _crypt32.CertFreeCertificateContext.argtypes = [_PCCERT_CONTEXT]
 _crypt32.CertFreeCertificateContext.restype = _BOOL
 
 _kernel32.CreateFileA.argtypes = [_LPCSTR, _DWORD, _DWORD, ctypes.c_void_p,
     _DWORD, _DWORD, _HANDLE]
 _kernel32.CreateFileA.restype = _HANDLE
 
 _kernel32.GetFileInformationByHandle.argtypes = [_HANDLE, ctypes.c_void_p]
 _kernel32.GetFileInformationByHandle.restype = _BOOL
 
 _kernel32.CloseHandle.argtypes = [_HANDLE]
 _kernel32.CloseHandle.restype = _BOOL
 
 try:
     _kernel32.CreateHardLinkA.argtypes = [_LPCSTR, _LPCSTR, ctypes.c_void_p]
     _kernel32.CreateHardLinkA.restype = _BOOL
 except AttributeError:
     pass
 
 _kernel32.SetFileAttributesA.argtypes = [_LPCSTR, _DWORD]
 _kernel32.SetFileAttributesA.restype = _BOOL
 
 _DRIVE_UNKNOWN = 0
 _DRIVE_NO_ROOT_DIR = 1
 _DRIVE_REMOVABLE = 2
 _DRIVE_FIXED = 3
 _DRIVE_REMOTE = 4
 _DRIVE_CDROM = 5
 _DRIVE_RAMDISK = 6
 
 _kernel32.GetDriveTypeA.argtypes = [_LPCSTR]
 _kernel32.GetDriveTypeA.restype = _UINT
 
 _kernel32.GetVolumeInformationA.argtypes = [_LPCSTR, ctypes.c_void_p, _DWORD,
     ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p, _DWORD]
 _kernel32.GetVolumeInformationA.restype = _BOOL
 
 _kernel32.GetVolumePathNameA.argtypes = [_LPCSTR, ctypes.c_void_p, _DWORD]
 _kernel32.GetVolumePathNameA.restype = _BOOL
 
 _kernel32.OpenProcess.argtypes = [_DWORD, _BOOL, _DWORD]
 _kernel32.OpenProcess.restype = _HANDLE
 
 _kernel32.GetExitCodeProcess.argtypes = [_HANDLE, ctypes.c_void_p]
 _kernel32.GetExitCodeProcess.restype = _BOOL
 
 _kernel32.GetLastError.argtypes = []
 _kernel32.GetLastError.restype = _DWORD
 
 _kernel32.GetModuleFileNameA.argtypes = [_HANDLE, ctypes.c_void_p, _DWORD]
 _kernel32.GetModuleFileNameA.restype = _DWORD
 
 _kernel32.CreateProcessA.argtypes = [_LPCSTR, _LPCSTR, ctypes.c_void_p,
     ctypes.c_void_p, _BOOL, _DWORD, ctypes.c_void_p, _LPCSTR, ctypes.c_void_p,
     ctypes.c_void_p]
 _kernel32.CreateProcessA.restype = _BOOL
 
 _kernel32.ExitProcess.argtypes = [_UINT]
 _kernel32.ExitProcess.restype = None
 
 _kernel32.GetCurrentProcessId.argtypes = []
 _kernel32.GetCurrentProcessId.restype = _DWORD
 
 _SIGNAL_HANDLER = ctypes.WINFUNCTYPE(_BOOL, _DWORD)
 _kernel32.SetConsoleCtrlHandler.argtypes = [_SIGNAL_HANDLER, _BOOL]
 _kernel32.SetConsoleCtrlHandler.restype = _BOOL
 
 _kernel32.SetConsoleMode.argtypes = [_HANDLE, _DWORD]
 _kernel32.SetConsoleMode.restype = _BOOL
 
 _kernel32.GetConsoleMode.argtypes = [_HANDLE, ctypes.c_void_p]
 _kernel32.GetConsoleMode.restype = _BOOL
 
 _kernel32.GetStdHandle.argtypes = [_DWORD]
 _kernel32.GetStdHandle.restype = _HANDLE
 
 _kernel32.GetConsoleScreenBufferInfo.argtypes = [_HANDLE, ctypes.c_void_p]
 _kernel32.GetConsoleScreenBufferInfo.restype = _BOOL
 
 _advapi32.GetUserNameA.argtypes = [ctypes.c_void_p, ctypes.c_void_p]
 _advapi32.GetUserNameA.restype = _BOOL
 
 _user32.GetWindowThreadProcessId.argtypes = [_HANDLE, ctypes.c_void_p]
 _user32.GetWindowThreadProcessId.restype = _DWORD
 
 _user32.ShowWindow.argtypes = [_HANDLE, ctypes.c_int]
 _user32.ShowWindow.restype = _BOOL
 
 _WNDENUMPROC = ctypes.WINFUNCTYPE(_BOOL, _HWND, _LPARAM)
 _user32.EnumWindows.argtypes = [_WNDENUMPROC, _LPARAM]
 _user32.EnumWindows.restype = _BOOL
 
 _kernel32.PeekNamedPipe.argtypes = [_HANDLE, ctypes.c_void_p, _DWORD,
     ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p]
 _kernel32.PeekNamedPipe.restype = _BOOL
 
 def _raiseoserror(name):
     # Force the code to a signed int to avoid an 'int too large' error.
     # See https://bugs.python.org/issue28474
     code = _kernel32.GetLastError()
     if code > 0x7fffffff:
         code -= 2**32
     err = ctypes.WinError(code=code)
     raise OSError(err.errno, '%s: %s' % (name,
                                          encoding.strtolocal(err.strerror)))
 
 def _getfileinfo(name):
     fh = _kernel32.CreateFileA(name, 0,
             _FILE_SHARE_READ | _FILE_SHARE_WRITE | _FILE_SHARE_DELETE,
             None, _OPEN_EXISTING, _FILE_FLAG_BACKUP_SEMANTICS, None)
     if fh == _INVALID_HANDLE_VALUE:
         _raiseoserror(name)
     try:
         fi = _BY_HANDLE_FILE_INFORMATION()
         if not _kernel32.GetFileInformationByHandle(fh, ctypes.byref(fi)):
             _raiseoserror(name)
         return fi
     finally:
         _kernel32.CloseHandle(fh)
 
 def checkcertificatechain(cert, build=True):
     '''Tests the given certificate to see if there is a complete chain to a
        trusted root certificate.  As a side effect, missing certificates are
        downloaded and installed unless ``build=False``.  True is returned if a
        chain to a trusted root exists (even if built on the fly), otherwise
        False.  NB: A chain to a trusted root does NOT imply that the certificate
        is valid.
     '''
 
     chainctxptr = ctypes.POINTER(CERT_CHAIN_CONTEXT)
 
     pchainctx = chainctxptr()
     chainpara = CERT_CHAIN_PARA(cbSize=ctypes.sizeof(CERT_CHAIN_PARA),
                                 RequestedUsage=CERT_USAGE_MATCH())
 
     certctx = _crypt32.CertCreateCertificateContext(X509_ASN_ENCODING, cert,
                                                     len(cert))
     if certctx is None:
         _raiseoserror('CertCreateCertificateContext')
 
     flags = 0
 
     if not build:
         flags |= 0x100  # CERT_CHAIN_DISABLE_AUTH_ROOT_AUTO_UPDATE
 
     try:
         # Building the certificate chain will update root certs as necessary.
         if not _crypt32.CertGetCertificateChain(None,      # hChainEngine
                                                 certctx,   # pCertContext
                                                 None,      # pTime
                                                 None,      # hAdditionalStore
                                                 ctypes.byref(chainpara),
                                                 flags,
                                                 None,      # pvReserved
                                                 ctypes.byref(pchainctx)):
             _raiseoserror('CertGetCertificateChain')
 
         chainctx = pchainctx.contents
 
         return chainctx.dwErrorStatus & CERT_TRUST_IS_PARTIAL_CHAIN == 0
     finally:
         if pchainctx:
             _crypt32.CertFreeCertificateChain(pchainctx)
         _crypt32.CertFreeCertificateContext(certctx)
 
 def oslink(src, dst):
     try:
         if not _kernel32.CreateHardLinkA(dst, src, None):
             _raiseoserror(src)
     except AttributeError: # Wine doesn't support this function
         _raiseoserror(src)
 
 def nlinks(name):
     '''return number of hardlinks for the given file'''
     return _getfileinfo(name).nNumberOfLinks
 
 def samefile(path1, path2):
     '''Returns whether path1 and path2 refer to the same file or directory.'''
     res1 = _getfileinfo(path1)
     res2 = _getfileinfo(path2)
     return (res1.dwVolumeSerialNumber == res2.dwVolumeSerialNumber
         and res1.nFileIndexHigh == res2.nFileIndexHigh
         and res1.nFileIndexLow == res2.nFileIndexLow)
 
 def samedevice(path1, path2):
     '''Returns whether path1 and path2 are on the same device.'''
     res1 = _getfileinfo(path1)
     res2 = _getfileinfo(path2)
     return res1.dwVolumeSerialNumber == res2.dwVolumeSerialNumber
 
 def peekpipe(pipe):
     handle = msvcrt.get_osfhandle(pipe.fileno())
     avail = _DWORD()
 
     if not _kernel32.PeekNamedPipe(handle, None, 0, None, ctypes.byref(avail),
                                    None):
         err = _kernel32.GetLastError()
         if err == _ERROR_BROKEN_PIPE:
             return 0
         raise ctypes.WinError(err)
 
     return avail.value
 
 def testpid(pid):
     '''return True if pid is still running or unable to
     determine, False otherwise'''
     h = _kernel32.OpenProcess(_PROCESS_QUERY_INFORMATION, False, pid)
     if h:
         try:
             status = _DWORD()
             if _kernel32.GetExitCodeProcess(h, ctypes.byref(status)):
                 return status.value == _STILL_ACTIVE
         finally:
             _kernel32.CloseHandle(h)
     return _kernel32.GetLastError() != _ERROR_INVALID_PARAMETER
 
 def executablepath():
     '''return full path of hg.exe'''
     size = 600
     buf = ctypes.create_string_buffer(size + 1)
     len = _kernel32.GetModuleFileNameA(None, ctypes.byref(buf), size)
     if len == 0:
         raise ctypes.WinError() # Note: WinError is a function
     elif len == size:
         raise ctypes.WinError(_ERROR_INSUFFICIENT_BUFFER)
     return buf.value
 
 def getvolumename(path):
     """Get the mount point of the filesystem from a directory or file
     (best-effort)
 
     Returns None if we are unsure. Raises OSError on ENOENT, EPERM, etc.
     """
     # realpath() calls GetFullPathName()
     realpath = os.path.realpath(path)
 
     size = len(realpath) + 1
     buf = ctypes.create_string_buffer(size)
 
     if not _kernel32.GetVolumePathNameA(realpath, ctypes.byref(buf), size):
         raise ctypes.WinError() # Note: WinError is a function
 
     return buf.value
 
 def getfstype(path):
     """Get the filesystem type name from a directory or file (best-effort)
 
     Returns None if we are unsure. Raises OSError on ENOENT, EPERM, etc.
     """
     volume = getvolumename(path)
 
     t = _kernel32.GetDriveTypeA(volume)
 
     if t == _DRIVE_REMOTE:
         return 'cifs'
     elif t not in (_DRIVE_REMOVABLE, _DRIVE_FIXED, _DRIVE_CDROM,
                    _DRIVE_RAMDISK):
         return None
 
-    size = 256
+    size = _MAX_PATH + 1
     name = ctypes.create_string_buffer(size)
 
     if not _kernel32.GetVolumeInformationA(volume, None, 0, None, None, None,
                                            ctypes.byref(name), size):
         raise ctypes.WinError() # Note: WinError is a function
 
     return name.value
 
 def getuser():
     '''return name of current user'''
     size = _DWORD(300)
     buf = ctypes.create_string_buffer(size.value + 1)
     if not _advapi32.GetUserNameA(ctypes.byref(buf), ctypes.byref(size)):
         raise ctypes.WinError()
     return buf.value
 
 _signalhandler = []
 
 def setsignalhandler():
     '''Register a termination handler for console events including
     CTRL+C. python signal handlers do not work well with socket
     operations.
     '''
     def handler(event):
         _kernel32.ExitProcess(1)
 
     if _signalhandler:
         return # already registered
     h = _SIGNAL_HANDLER(handler)
     _signalhandler.append(h) # needed to prevent garbage collection
     if not _kernel32.SetConsoleCtrlHandler(h, True):
         raise ctypes.WinError()
 
 def hidewindow():
 
     def callback(hwnd, pid):
         wpid = _DWORD()
         _user32.GetWindowThreadProcessId(hwnd, ctypes.byref(wpid))
         if pid == wpid.value:
             _user32.ShowWindow(hwnd, _SW_HIDE)
             return False # stop enumerating windows
         return True
 
     pid = _kernel32.GetCurrentProcessId()
     _user32.EnumWindows(_WNDENUMPROC(callback), pid)
 
 def termsize():
     # cmd.exe does not handle CR like a unix console, the CR is
     # counted in the line length. On 80 columns consoles, if 80
     # characters are written, the following CR won't apply on the
     # current line but on the new one. Keep room for it.
     width = 80 - 1
     height = 25
     # Query stderr to avoid problems with redirections
     screenbuf = _kernel32.GetStdHandle(
                   _STD_ERROR_HANDLE) # don't close the handle returned
     if screenbuf is None or screenbuf == _INVALID_HANDLE_VALUE:
         return width, height
     csbi = _CONSOLE_SCREEN_BUFFER_INFO()
     if not _kernel32.GetConsoleScreenBufferInfo(
                         screenbuf, ctypes.byref(csbi)):
         return width, height
     width = csbi.srWindow.Right - csbi.srWindow.Left  # don't '+ 1'
     height = csbi.srWindow.Bottom - csbi.srWindow.Top + 1
     return width, height
 
 def enablevtmode():
     '''Enable virtual terminal mode for the associated console.  Return True if
     enabled, else False.'''
 
     ENABLE_VIRTUAL_TERMINAL_PROCESSING = 0x4
 
     handle = _kernel32.GetStdHandle(_STD_OUTPUT_HANDLE) # don't close the handle
     if handle == _INVALID_HANDLE_VALUE:
         return False
 
     mode = _DWORD(0)
 
     if not _kernel32.GetConsoleMode(handle, ctypes.byref(mode)):
         return False
 
     if (mode.value & ENABLE_VIRTUAL_TERMINAL_PROCESSING) == 0:
         mode.value |= ENABLE_VIRTUAL_TERMINAL_PROCESSING
 
         if not _kernel32.SetConsoleMode(handle, mode):
             return False
 
     return True
 
 def spawndetached(args):
     # No standard library function really spawns a fully detached
     # process under win32 because they allocate pipes or other objects
     # to handle standard streams communications. Passing these objects
     # to the child process requires handle inheritance to be enabled
     # which makes really detached processes impossible.
     si = _STARTUPINFO()
     si.cb = ctypes.sizeof(_STARTUPINFO)
 
     pi = _PROCESS_INFORMATION()
 
     env = ''
     for k in encoding.environ:
         env += "%s=%s\0" % (k, encoding.environ[k])
     if not env:
         env = '\0'
     env += '\0'
 
     args = subprocess.list2cmdline(args)
 
     res = _kernel32.CreateProcessA(
         None, args, None, None, False, _CREATE_NO_WINDOW,
         env, pycompat.getcwd(), ctypes.byref(si), ctypes.byref(pi))
     if not res:
         raise ctypes.WinError()
 
     return pi.dwProcessId
 
 def unlink(f):
     '''try to implement POSIX' unlink semantics on Windows'''
 
     if os.path.isdir(f):
         # use EPERM because it is POSIX prescribed value, even though
         # unlink(2) on directories returns EISDIR on Linux
         raise IOError(errno.EPERM,
                       "Unlinking directory not permitted: '%s'" % f)
 
     # POSIX allows to unlink and rename open files. Windows has serious
     # problems with doing that:
     # - Calling os.unlink (or os.rename) on a file f fails if f or any
     #   hardlinked copy of f has been opened with Python's open(). There is no
     #   way such a file can be deleted or renamed on Windows (other than
     #   scheduling the delete or rename for the next reboot).
     # - Calling os.unlink on a file that has been opened with Mercurial's
     #   posixfile (or comparable methods) will delay the actual deletion of
     #   the file for as long as the file is held open. The filename is blocked
     #   during that time and cannot be used for recreating a new file under
     #   that same name ("zombie file"). Directories containing such zombie files
     #   cannot be removed or moved.
     # A file that has been opened with posixfile can be renamed, so we rename
     # f to a random temporary name before calling os.unlink on it. This allows
     # callers to recreate f immediately while having other readers do their
     # implicit zombie filename blocking on a temporary name.
 
     for tries in xrange(10):
         temp = '%s-%08x' % (f, random.randint(0, 0xffffffff))
         try:
             os.rename(f, temp)  # raises OSError EEXIST if temp exists
             break
         except OSError as e:
             if e.errno != errno.EEXIST:
                 raise
     else:
         raise IOError(errno.EEXIST, "No usable temporary filename found")
 
     try:
         os.unlink(temp)
     except OSError:
         # The unlink might have failed because the READONLY attribute may heave
         # been set on the original file. Rename works fine with READONLY set,
         # but not os.unlink. Reset all attributes and try again.
         _kernel32.SetFileAttributesA(temp, _FILE_ATTRIBUTE_NORMAL)
         try:
             os.unlink(temp)
         except OSError:
             # The unlink might have failed due to some very rude AV-Scanners.
             # Leaking a tempfile is the lesser evil than aborting here and
             # leaving some potentially serious inconsistencies.
             pass
 
 def makedir(path, notindexed):
     os.mkdir(path)
     if notindexed:
         _kernel32.SetFileAttributesA(path, _FILE_ATTRIBUTE_NOT_CONTENT_INDEXED)