win32: move lookupreg() to windows.py

lookupreg() doesn't use the win32 API directly any more, it uses the Python
standard library module _winreg.

mercurial/win32.py

@@ -1,418 +1,396
 # 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.
 
-import encoding
-import ctypes, errno, os, subprocess, random, _winreg
+import ctypes, errno, os, subprocess, random
 
 _kernel32 = ctypes.windll.kernel32
 _advapi32 = ctypes.windll.advapi32
 _user32 = ctypes.windll.user32
 
 _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
 
 _INVALID_HANDLE_VALUE = _HANDLE(-1).value
 
 # GetLastError
 _ERROR_SUCCESS = 0
 _ERROR_INVALID_PARAMETER = 87
 _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
 
 # 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)]
 
 _DETACHED_PROCESS = 0x00000008
 _STARTF_USESHOWWINDOW = 0x00000001
 _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_ERROR_HANDLE = _DWORD(-12).value
 
 # types of parameters of C functions used (required by pypy)
 
 _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
 
 _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.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
 
 def _raiseoserror(name):
     err = ctypes.WinError()
     raise OSError(err.errno, '%s: %s' % (name, err.strerror))
 
 def _getfileinfo(name):
     fh = _kernel32.CreateFileA(name, 0,
             _FILE_SHARE_READ | _FILE_SHARE_WRITE | _FILE_SHARE_DELETE,
             None, _OPEN_EXISTING, 0, 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 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(fpath1, fpath2):
     '''Returns whether fpath1 and fpath2 refer to the same file. This is only
     guaranteed to work for files, not directories.'''
     res1 = _getfileinfo(fpath1)
     res2 = _getfileinfo(fpath2)
     return (res1.dwVolumeSerialNumber == res2.dwVolumeSerialNumber
         and res1.nFileIndexHigh == res2.nFileIndexHigh
         and res1.nFileIndexLow == res2.nFileIndexLow)
 
 def samedevice(fpath1, fpath2):
     '''Returns whether fpath1 and fpath2 are on the same device. This is only
     guaranteed to work for files, not directories.'''
     res1 = _getfileinfo(fpath1)
     res2 = _getfileinfo(fpath2)
     return res1.dwVolumeSerialNumber == res2.dwVolumeSerialNumber
 
 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 lookupreg(key, valname=None, scope=None):
-    ''' Look up a key/value name in the Windows registry.
-
-    valname: value name. If unspecified, the default value for the key
-    is used.
-    scope: optionally specify scope for registry lookup, this can be
-    a sequence of scopes to look up in order. Default (CURRENT_USER,
-    LOCAL_MACHINE).
-    '''
-    if scope is None:
-        scope = (_winreg.HKEY_CURRENT_USER, _winreg.HKEY_LOCAL_MACHINE)
-    elif not isinstance(scope, (list, tuple)):
-        scope = (scope,)
-    for s in scope:
-        try:
-            val = _winreg.QueryValueEx(_winreg.OpenKey(s, key), valname)[0]
-            # never let a Unicode string escape into the wild
-            return encoding.tolocal(val.encode('UTF-8'))
-        except EnvironmentError:
-            pass
-
 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
     elif len == size:
         raise ctypes.WinError(_ERROR_INSUFFICIENT_BUFFER)
     return buf.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 termwidth():
     # 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 = 79
     # 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
     csbi = _CONSOLE_SCREEN_BUFFER_INFO()
     if not _kernel32.GetConsoleScreenBufferInfo(
                         screenbuf, ctypes.byref(csbi)):
         return width
     width = csbi.srWindow.Right - csbi.srWindow.Left
     return width
 
 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)
     si.dwFlags = _STARTF_USESHOWWINDOW
     si.wShowWindow = _SW_HIDE
 
     pi = _PROCESS_INFORMATION()
 
     env = ''
     for k in os.environ:
         env += "%s=%s\0" % (k, os.environ[k])
     if not env:
         env = '\0'
     env += '\0'
 
     args = subprocess.list2cmdline(args)
     # Not running the command in shell mode makes python26 hang when
     # writing to hgweb output socket.
     comspec = os.environ.get("COMSPEC", "cmd.exe")
     args = comspec + " /c " + args
 
     res = _kernel32.CreateProcessA(
         None, args, None, None, False, _DETACHED_PROCESS,
         env, os.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'''
 
     # 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, 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)

mercurial/windows.py

@@ -1,319 +1,339
 # windows.py - Windows utility function implementations for Mercurial
 #
 #  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 i18n import _
-import osutil
-import errno, msvcrt, os, re, sys
+import osutil, encoding
+import errno, msvcrt, os, re, sys, _winreg
 
 import win32
 executablepath = win32.executablepath
 getuser = win32.getuser
 hidewindow = win32.hidewindow
-lookupreg = win32.lookupreg
 makedir = win32.makedir
 nlinks = win32.nlinks
 oslink = win32.oslink
 samedevice = win32.samedevice
 samefile = win32.samefile
 setsignalhandler = win32.setsignalhandler
 spawndetached = win32.spawndetached
 termwidth = win32.termwidth
 testpid = win32.testpid
 unlink = win32.unlink
 
 nulldev = 'NUL:'
 umask = 0022
 
 # wrap osutil.posixfile to provide friendlier exceptions
 def posixfile(name, mode='r', buffering=-1):
     try:
         return osutil.posixfile(name, mode, buffering)
     except WindowsError, err:
         raise IOError(err.errno, '%s: %s' % (name, err.strerror))
 posixfile.__doc__ = osutil.posixfile.__doc__
 
 class winstdout(object):
     '''stdout on windows misbehaves if sent through a pipe'''
 
     def __init__(self, fp):
         self.fp = fp
 
     def __getattr__(self, key):
         return getattr(self.fp, key)
 
     def close(self):
         try:
             self.fp.close()
         except IOError:
             pass
 
     def write(self, s):
         try:
             # This is workaround for "Not enough space" error on
             # writing large size of data to console.
             limit = 16000
             l = len(s)
             start = 0
             self.softspace = 0
             while start < l:
                 end = start + limit
                 self.fp.write(s[start:end])
                 start = end
         except IOError, inst:
             if inst.errno != 0:
                 raise
             self.close()
             raise IOError(errno.EPIPE, 'Broken pipe')
 
     def flush(self):
         try:
             return self.fp.flush()
         except IOError, inst:
             if inst.errno != errno.EINVAL:
                 raise
             self.close()
             raise IOError(errno.EPIPE, 'Broken pipe')
 
 sys.__stdout__ = sys.stdout = winstdout(sys.stdout)
 
 def _is_win_9x():
     '''return true if run on windows 95, 98 or me.'''
     try:
         return sys.getwindowsversion()[3] == 1
     except AttributeError:
         return 'command' in os.environ.get('comspec', '')
 
 def openhardlinks():
     return not _is_win_9x()
 
 def parsepatchoutput(output_line):
     """parses the output produced by patch and returns the filename"""
     pf = output_line[14:]
     if pf[0] == '`':
         pf = pf[1:-1] # Remove the quotes
     return pf
 
 def sshargs(sshcmd, host, user, port):
     '''Build argument list for ssh or Plink'''
     pflag = 'plink' in sshcmd.lower() and '-P' or '-p'
     args = user and ("%s@%s" % (user, host)) or host
     return port and ("%s %s %s" % (args, pflag, port)) or args
 
 def setflags(f, l, x):
     pass
 
 def copymode(src, dst, mode=None):
     pass
 
 def checkexec(path):
     return False
 
 def checklink(path):
     return False
 
 def setbinary(fd):
     # When run without console, pipes may expose invalid
     # fileno(), usually set to -1.
     fno = getattr(fd, 'fileno', None)
     if fno is not None and fno() >= 0:
         msvcrt.setmode(fno(), os.O_BINARY)
 
 def pconvert(path):
     return path.replace(os.sep, '/')
 
 def localpath(path):
     return path.replace('/', '\\')
 
 def normpath(path):
     return pconvert(os.path.normpath(path))
 
 encodinglower = None
 encodingupper = None
 
 def normcase(path):
     return encodingupper(path)
 
 def realpath(path):
     '''
     Returns the true, canonical file system path equivalent to the given
     path.
     '''
     # TODO: There may be a more clever way to do this that also handles other,
     # less common file systems.
     return os.path.normpath(normcase(os.path.realpath(path)))
 
 def samestat(s1, s2):
     return False
 
 # A sequence of backslashes is special iff it precedes a double quote:
 # - if there's an even number of backslashes, the double quote is not
 #   quoted (i.e. it ends the quoted region)
 # - if there's an odd number of backslashes, the double quote is quoted
 # - in both cases, every pair of backslashes is unquoted into a single
 #   backslash
 # (See http://msdn2.microsoft.com/en-us/library/a1y7w461.aspx )
 # So, to quote a string, we must surround it in double quotes, double
 # the number of backslashes that preceed double quotes and add another
 # backslash before every double quote (being careful with the double
 # quote we've appended to the end)
 _quotere = None
 def shellquote(s):
     global _quotere
     if _quotere is None:
         _quotere = re.compile(r'(\\*)("|\\$)')
     return '"%s"' % _quotere.sub(r'\1\1\\\2', s)
 
 def quotecommand(cmd):
     """Build a command string suitable for os.popen* calls."""
     if sys.version_info < (2, 7, 1):
         # Python versions since 2.7.1 do this extra quoting themselves
         return '"' + cmd + '"'
     return cmd
 
 def popen(command, mode='r'):
     # Work around "popen spawned process may not write to stdout
     # under windows"
     # http://bugs.python.org/issue1366
     command += " 2> %s" % nulldev
     return os.popen(quotecommand(command), mode)
 
 def explainexit(code):
     return _("exited with status %d") % code, code
 
 # if you change this stub into a real check, please try to implement the
 # username and groupname functions above, too.
 def isowner(st):
     return True
 
 def findexe(command):
     '''Find executable for command searching like cmd.exe does.
     If command is a basename then PATH is searched for command.
     PATH isn't searched if command is an absolute or relative path.
     An extension from PATHEXT is found and added if not present.
     If command isn't found None is returned.'''
     pathext = os.environ.get('PATHEXT', '.COM;.EXE;.BAT;.CMD')
     pathexts = [ext for ext in pathext.lower().split(os.pathsep)]
     if os.path.splitext(command)[1].lower() in pathexts:
         pathexts = ['']
 
     def findexisting(pathcommand):
         'Will append extension (if needed) and return existing file'
         for ext in pathexts:
             executable = pathcommand + ext
             if os.path.exists(executable):
                 return executable
         return None
 
     if os.sep in command:
         return findexisting(command)
 
     for path in os.environ.get('PATH', '').split(os.pathsep):
         executable = findexisting(os.path.join(path, command))
         if executable is not None:
             return executable
     return findexisting(os.path.expanduser(os.path.expandvars(command)))
 
 def statfiles(files):
     '''Stat each file in files and yield stat or None if file does not exist.
     Cluster and cache stat per directory to minimize number of OS stat calls.'''
     dircache = {} # dirname -> filename -> status | None if file does not exist
     for nf in files:
         nf  = normcase(nf)
         dir, base = os.path.split(nf)
         if not dir:
             dir = '.'
         cache = dircache.get(dir, None)
         if cache is None:
             try:
                 dmap = dict([(normcase(n), s)
                     for n, k, s in osutil.listdir(dir, True)])
             except OSError, err:
                 # handle directory not found in Python version prior to 2.5
                 # Python <= 2.4 returns native Windows code 3 in errno
                 # Python >= 2.5 returns ENOENT and adds winerror field
                 # EINVAL is raised if dir is not a directory.
                 if err.errno not in (3, errno.ENOENT, errno.EINVAL,
                                      errno.ENOTDIR):
                     raise
                 dmap = {}
             cache = dircache.setdefault(dir, dmap)
         yield cache.get(base, None)
 
 def username(uid=None):
     """Return the name of the user with the given uid.
 
     If uid is None, return the name of the current user."""
     return None
 
 def groupname(gid=None):
     """Return the name of the group with the given gid.
 
     If gid is None, return the name of the current group."""
     return None
 
 def _removedirs(name):
     """special version of os.removedirs that does not remove symlinked
     directories or junction points if they actually contain files"""
     if osutil.listdir(name):
         return
     os.rmdir(name)
     head, tail = os.path.split(name)
     if not tail:
         head, tail = os.path.split(head)
     while head and tail:
         try:
             if osutil.listdir(head):
                 return
             os.rmdir(head)
         except (ValueError, OSError):
             break
         head, tail = os.path.split(head)
 
 def unlinkpath(f):
     """unlink and remove the directory if it is empty"""
     unlink(f)
     # try removing directories that might now be empty
     try:
         _removedirs(os.path.dirname(f))
     except OSError:
         pass
 
 def rename(src, dst):
     '''atomically rename file src to dst, replacing dst if it exists'''
     try:
         os.rename(src, dst)
     except OSError, e:
         if e.errno != errno.EEXIST:
             raise
         unlink(dst)
         os.rename(src, dst)
 
 def gethgcmd():
     return [sys.executable] + sys.argv[:1]
 
 def termwidth():
     # 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.
     return 79
 
 def groupmembers(name):
     # Don't support groups on Windows for now
     raise KeyError
 
 def isexec(f):
     return False
 
 class cachestat(object):
     def __init__(self, path):
         pass
 
     def cacheable(self):
         return False
 
+def lookupreg(key, valname=None, scope=None):
+    ''' Look up a key/value name in the Windows registry.
+
+    valname: value name. If unspecified, the default value for the key
+    is used.
+    scope: optionally specify scope for registry lookup, this can be
+    a sequence of scopes to look up in order. Default (CURRENT_USER,
+    LOCAL_MACHINE).
+    '''
+    if scope is None:
+        scope = (_winreg.HKEY_CURRENT_USER, _winreg.HKEY_LOCAL_MACHINE)
+    elif not isinstance(scope, (list, tuple)):
+        scope = (scope,)
+    for s in scope:
+        try:
+            val = _winreg.QueryValueEx(_winreg.OpenKey(s, key), valname)[0]
+            # never let a Unicode string escape into the wild
+            return encoding.tolocal(val.encode('UTF-8'))
+        except EnvironmentError:
+            pass
+
 expandglobs = True