win32: optimize parameters for the CreateFile call in _getfileinfo

Set dwDesiredAccess to 0 instead of GENERIC_READ.
Zero is  enough for querying the file metadata. We don't even need to
access the -contents- of the file.

Set dwShareMode to FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE
instead of the overly restrictive FILE_SHARE_READ.
There is no need to cause write or delete accesses by other processes to
fail while we are querying file metadata.

See http://msdn.microsoft.com/en-us/library/aa363858(v=vs.85).aspx

mercurial/win32.py

@@ -1,182 +1,183 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.
 
 """Utility functions that use win32 API.
 
 Mark Hammond's win32all package allows better functionality on
 Windows. This module overrides definitions in util.py. If not
 available, import of this module will fail, and generic code will be
 used.
 """
 
 import win32api
 
 import errno, os, sys, pywintypes, win32con, win32file, win32process
 import winerror, win32gui, win32console
 import osutil, encoding
 from win32com.shell import shell, shellcon
 
 def os_link(src, dst):
     try:
         win32file.CreateHardLink(dst, src)
     except pywintypes.error:
         raise OSError(errno.EINVAL, 'target implements hardlinks improperly')
     except NotImplementedError: # Another fake error win Win98
         raise OSError(errno.EINVAL, 'Hardlinking not supported')
 
 def _getfileinfo(pathname):
     """Return number of hardlinks for the given file."""
     try:
-        fh = win32file.CreateFile(pathname,
-            win32file.GENERIC_READ, win32file.FILE_SHARE_READ,
+        fh = win32file.CreateFile(pathname, 0,
+            win32file.FILE_SHARE_READ | win32file.FILE_SHARE_WRITE |
+            win32file.FILE_SHARE_DELETE,
             None, win32file.OPEN_EXISTING, 0, None)
     except pywintypes.error:
         raise OSError(errno.ENOENT, 'The system cannot find the file specified')
     try:
         return win32file.GetFileInformationByHandle(fh)
     finally:
         fh.Close()
 
 def nlinks(pathname):
     """Return number of hardlinks for the given file."""
     return _getfileinfo(pathname)[7]
 
 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)
     # Index 4 is the volume serial number, and 8 and 9 contain the file ID
     return res1[4] == res2[4] and res1[8] == res2[8] and res1[9] == res2[9]
 
 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[4] == res2[4]
 
 def testpid(pid):
     '''return True if pid is still running or unable to
     determine, False otherwise'''
     try:
         handle = win32api.OpenProcess(
             win32con.PROCESS_QUERY_INFORMATION, False, pid)
         if handle:
             status = win32process.GetExitCodeProcess(handle)
             return status == win32con.STILL_ACTIVE
     except pywintypes.error, details:
         return details[0] != winerror.ERROR_INVALID_PARAMETER
     return True
 
 def lookup_reg(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).
     '''
     try:
         from _winreg import HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE, \
             QueryValueEx, OpenKey
     except ImportError:
         return None
 
     if scope is None:
         scope = (HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE)
     elif not isinstance(scope, (list, tuple)):
         scope = (scope,)
     for s in scope:
         try:
             val = QueryValueEx(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 system_rcpath_win32():
     '''return default os-specific hgrc search path'''
     filename = win32api.GetModuleFileName(0)
     # Use mercurial.ini found in directory with hg.exe
     progrc = os.path.join(os.path.dirname(filename), 'mercurial.ini')
     if os.path.isfile(progrc):
         return [progrc]
     # Use hgrc.d found in directory with hg.exe
     progrcd = os.path.join(os.path.dirname(filename), 'hgrc.d')
     if os.path.isdir(progrcd):
         rcpath = []
         for f, kind in osutil.listdir(progrcd):
             if f.endswith('.rc'):
                 rcpath.append(os.path.join(progrcd, f))
         return rcpath
     # else look for a system rcpath in the registry
     try:
         value = win32api.RegQueryValue(
                 win32con.HKEY_LOCAL_MACHINE, 'SOFTWARE\\Mercurial')
         rcpath = []
         for p in value.split(os.pathsep):
             if p.lower().endswith('mercurial.ini'):
                 rcpath.append(p)
             elif os.path.isdir(p):
                 for f, kind in osutil.listdir(p):
                     if f.endswith('.rc'):
                         rcpath.append(os.path.join(p, f))
         return rcpath
     except pywintypes.error:
         return []
 
 def user_rcpath_win32():
     '''return os-specific hgrc search path to the user dir'''
     userdir = os.path.expanduser('~')
     if sys.getwindowsversion()[3] != 2 and userdir == '~':
         # We are on win < nt: fetch the APPDATA directory location and use
         # the parent directory as the user home dir.
         appdir = shell.SHGetPathFromIDList(
             shell.SHGetSpecialFolderLocation(0, shellcon.CSIDL_APPDATA))
         userdir = os.path.dirname(appdir)
     return [os.path.join(userdir, 'mercurial.ini'),
             os.path.join(userdir, '.hgrc')]
 
 def getuser():
     '''return name of current user'''
     return win32api.GetUserName()
 
 def set_signal_handler_win32():
     """Register a termination handler for console events including
     CTRL+C. python signal handlers do not work well with socket
     operations.
     """
     def handler(event):
         win32process.ExitProcess(1)
     win32api.SetConsoleCtrlHandler(handler)
 
 def hidewindow():
     def callback(*args, **kwargs):
         hwnd, pid = args
         wpid = win32process.GetWindowThreadProcessId(hwnd)[1]
         if pid == wpid:
             win32gui.ShowWindow(hwnd, win32con.SW_HIDE)
 
     pid =  win32process.GetCurrentProcessId()
     win32gui.EnumWindows(callback, pid)
 
 def termwidth():
     try:
         # Query stderr to avoid problems with redirections
         screenbuf = win32console.GetStdHandle(win32console.STD_ERROR_HANDLE)
         if screenbuf is None:
             return 79
         try:
             window = screenbuf.GetConsoleScreenBufferInfo()['Window']
             width = window.Right - window.Left
             return width
         finally:
             screenbuf.Detach()
     except pywintypes.error:
         return 79