diff --git a/hgext/win32mbcs.py b/hgext/win32mbcs.py
new file mode 100644
--- /dev/null
+++ b/hgext/win32mbcs.py
@@ -0,0 +1,158 @@
+# win32mbcs.py -- MBCS filename support for Mercurial on Windows
+#
+# Copyright (c) 2008 Shun-ichi Goto <shunichi.goto@gmail.com>
+#
+# Version: 0.1
+# Author:  Shun-ichi Goto <shunichi.goto@gmail.com>
+#
+# This software may be used and distributed according to the terms
+# of the GNU General Public License, incorporated herein by reference.
+#
+"""Allow to use shift_jis/big5 filenames on Windows.
+
+There is a well known issue "0x5c problem" on Windows.  It is a
+trouble on handling path name as raw encoded byte sequence of
+problematic encodings like shift_jis or big5.  The primary intent
+of this extension is to allow using such a encoding on Mercurial
+without strange file operation error.
+
+By enabling this extension, hook mechanism is activated and some
+functions are altered.  Usually, this encoding is your local encoding
+on your system by default. So you can get benefit simply by enabling
+this extension.
+
+The encoding for filename is same one for terminal by default.  You
+can change the encoding by setting HGENCODING environment variable.
+
+This extension is usefull for:
+ * Japanese Windows user using shift_jis encoding.
+ * Chinese Windows user using big5 encoding.
+ * Users who want to use a repository created with such a encoding.
+
+Note: Unix people does not need to use this extension.
+
+"""
+
+import os
+from mercurial.i18n import _
+from mercurial import util
+
+__all__ = ['install', 'uninstall', 'reposetup']
+
+
+# codec and alias names of sjis and big5 to be faked.
+_problematic_encodings = util.frozenset([
+        'big5', 'big5-tw', 'csbig5',
+        'big5hkscs', 'big5-hkscs', 'hkscs',
+        'cp932', '932', 'ms932', 'mskanji', 'ms-kanji',
+        'shift_jis', 'csshiftjis', 'shiftjis', 'sjis', 's_jis',
+        'shift_jis_2004', 'shiftjis2004', 'sjis_2004', 'sjis2004',
+        'shift_jisx0213', 'shiftjisx0213', 'sjisx0213', 's_jisx0213',
+        ])
+
+# attribute name to store original function
+_ORIGINAL = '_original'
+
+_ui = None
+
+def decode_with_check(arg):
+    if isinstance(arg, tuple):
+        return tuple(map(decode_with_check, arg))
+    elif isinstance(arg, list):
+        return map(decode_with_check, arg)
+    elif isinstance(arg, str):
+        uarg = arg.decode(util._encoding)
+        if arg == uarg.encode(util._encoding):
+            return uarg
+        else:
+            raise UnicodeError("Not local encoding")
+    else:
+        return arg
+
+def encode_with_check(arg):
+    if isinstance(arg, tuple):
+        return tuple(map(encode_with_check, arg))
+    elif isinstance(arg, list):
+        return map(encode_with_check, arg)
+    elif isinstance(arg, unicode):
+        ret = arg.encode(util._encoding)
+        return ret
+    else:
+        return arg
+
+def wrap(func):
+    
+    def wrapped(*args):
+        # check argument is unicode, then call original
+        for arg in args:
+            if isinstance(arg, unicode):
+                return func(*args)
+        # make decoded argument list into uargs
+        try:
+            args = decode_with_check(args)
+        except UnicodeError, exc:
+            # If not encoded with _local_fs_encoding, report it then
+            # continue with calling original function.
+            _ui.warn(_("WARNING: [win32mbcs] filename conversion fail for" +
+                     " %s: '%s'\n") % (util._encoding, args))
+            return func(*args)
+        # call as unicode operation, then return with encoding
+        return encode_with_check(func(*args))
+
+    # fake is only for relevant environment.
+    if hasattr(func, _ORIGINAL) or \
+            util._encoding.lower() not in _problematic_encodings:
+        return func
+    else:
+        f = wrapped
+        f.__name__ = func.__name__
+        setattr(f, _ORIGINAL, func)   # hold original to restore
+        return f
+
+def unwrap(func):
+    return getattr(func, _ORIGINAL, func)
+
+def install():
+    # wrap some python functions and mercurial functions
+    # to handle raw bytes on Windows.
+    # NOTE: dirname and basename is safe because they use result
+    # of os.path.split()
+    global _ui
+    if not _ui:
+        from mercurial import ui
+        _ui = ui.ui()
+    os.path.join = wrap(os.path.join)
+    os.path.split = wrap(os.path.split) 
+    os.path.splitext = wrap(os.path.splitext)
+    os.path.splitunc = wrap(os.path.splitunc)
+    os.path.normpath = wrap(os.path.normpath)
+    os.path.normcase = wrap(os.path.normcase)
+    os.makedirs = wrap(os.makedirs)
+    util.endswithsep = wrap(util.endswithsep)
+    util.splitpath = wrap(util.splitpath)
+
+def uninstall():
+    # restore original functions.
+    os.path.join = unwrap(os.path.join)
+    os.path.split = unwrap(os.path.split) 
+    os.path.splitext = unwrap(os.path.splitext)
+    os.path.splitunc = unwrap(os.path.splitunc)
+    os.path.normpath = unwrap(os.path.normpath)
+    os.path.normcase = unwrap(os.path.normcase)
+    os.makedirs = unwrap(os.makedirs)
+    util.endswithsep = unwrap(util.endswithsep)
+    util.splitpath = unwrap(util.splitpath)
+
+
+def reposetup(ui, repo):
+    # TODO: decide use of config section for this extension
+    global _ui
+    _ui = ui
+    if not os.path.supports_unicode_filenames:
+        ui.warn(_("[win32mbcs] cannot activate on this platform.\n"))
+        return
+    # install features of this extension
+    install()
+    ui.debug(_("[win32mbcs] activeted with encoding: %s\n") % util._encoding)
+
+# win32mbcs.py ends here