mercurial/win32.py

win32: correctly break hardlinks on network drives (issue761)

win32.nlinks() was often returning 1 instead of the correct
hardlinks count when reading from network drives. This made
commit or push to a repository on a network share to fail
breaking the hardlinks in the datastore, possibly causing
integrity errors in repositories linked locally on the remote
side.

Here is what the MSDN says about GetFileInformationByHandle():

  Depending on the underlying network features of the operating
  system and the type of server connected to, the
  GetFileInformationByHandle function may fail, return partial
  information, or full information for the given file.

In practice, we never got the correct hardlinks count when
reading from and to many combinations of Window XP, 2003, Vista
and 7, via network drives or RDP shares. It always returned 1
instead. The only setup returning an accurate links count was a
samba on Debian.

To avoid this, Mercurial now breaks the hardlinks unconditionally
when writing to a network drive.

# 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,
            None, win32file.OPEN_EXISTING, 0, None)
        try:
            return win32file.GetFileInformationByHandle(fh)
        finally:
            fh.Close()
    except pywintypes.error:
        return None

def nlinks(pathname):
    """Return number of hardlinks for the given file."""
    res = _getfileinfo(pathname)
    if res is not None:
        links = res[7]
    else:
        links = os.lstat(pathname).st_nlink
    if links < 2:
        # Known to be wrong for most network drives
        dirname = os.path.dirname(pathname)
        if not dirname:
            dirname = '.'
        dt = win32file.GetDriveType(dirname + '\\')
        if dt == 4 or dt == 1:
            # Fake hardlink to force COW for network drives
            links = 2
    return links

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)
    if res1 is not None and res2 is not None:
        # 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]
    else:
        return False

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)
    if res1 is not None and res2 is not None:
        return res1[4] == res2[4]
    else:
        return False

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'''
    proc = win32api.GetCurrentProcess()
    try:
        # This will fail on windows < NT
        filename = win32process.GetModuleFileNameEx(proc, 0)
    except:
        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)
        try:
            window = screenbuf.GetConsoleScreenBufferInfo()['Window']
            width = window.Right - window.Left
            return width
        finally:
            screenbuf.Detach()
    except pywintypes.error:
        return 79