~azzar1/unity/add-show-desktop-key

# IVLE - Informatics Virtual Learning Environment

# Copyright (C) 2007-2008 The University of Melbourne

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

# Module: util

# Author: Matt Giuca

# Date: 12/12/2007

# Contains common utility functions.

import os

import sys

import stat

class IVLEError(Exception):

    """Legacy general IVLE exception.

    This is the old "standard" exception class for IVLE errors. It is only

    used in fileservice, and should not be used in any new code.

    """

    def __init__(self, httpcode, message=None):

        self.httpcode = httpcode

        self.message = message

        self.args = (httpcode, message)

class IVLEJailError(Exception):

    """Exception proxying an in-jail error.

    This exception indicates an error that occurred inside an IVLE CGI script

    inside the jail. It should never be raised directly - only by the 

    interpreter.

    Information will be retrieved from it, and then treated as a normal

    error.

    """

    def __init__(self, type_str, message, info):

        self.type_str = type_str

        self.message = message

        self.info = info

class FakeObject(object):

    """ A representation of an object that can't be Pickled """

    def __init__(self, type, name, attrib={}):

        self.type = type

        self.name = name

        self.attrib = attrib

    def __repr__(self):

        return "<Fake %s %s>"%(self.type, self.name)

def split_path(path):

    """Given a path, returns a tuple consisting of the top-level directory in

    the path, and the rest of the path. Note that both items in the tuple will

    NOT begin with a slash, regardless of whether the original path did. Also

    normalises the path.

    Always returns a pair of strings, except for one special case, in which

    the path is completely empty (or just a single slash). In this case the

    return value will be (None, ''). But still always returns a pair.

    Examples:

    >>> split_path("")

    (None, '')

    >>> split_path("/")

    (None, '')

    >>> split_path("home")

    ('home', '')

    >>> split_path("home/docs/files")

    ('home', 'docs/files')

    >>> split_path("//home/docs/files")

    ('', 'home/docs/files')

    """

    path = os.path.normpath(path)

    # Ignore the opening slash

    if path.startswith(os.sep):

        path = path[len(os.sep):]

    if path == '' or path == '.':

        return (None, '')

    splitpath = path.split(os.sep, 1)

    if len(splitpath) == 1:

        return (splitpath[0], '')

    else:

        return tuple(splitpath)

def relpath(path, start=os.path.curdir):

    """Return a relative version of a path.

    XXX Backported from Python 2.6 posixpath.py.

    """

    if not path:

        raise ValueError("no path specified")

    start_list = os.path.abspath(start).split(os.path.sep)

    path_list = os.path.abspath(path).split(os.path.sep)

    # Work out how much of the filepath is shared by start and path.

    i = len(os.path.commonprefix([start_list, path_list]))

    rel_list = [os.path.pardir] * (len(start_list)-i) + path_list[i:]

    if not rel_list:

        return os.path.curdir

    return os.path.join(*rel_list)

def incomplete_utf8_sequence(byteseq):

    """Calculate the completeness of a UTF-8 encoded string.

    Given a UTF-8-encoded byte sequence (str), returns the number of bytes at

    the end of the string which comprise an incomplete UTF-8 character

    sequence.

    If the string is empty or ends with a complete character OR INVALID

    sequence, returns 0.

    Otherwise, returns 1-3 indicating the number of bytes in the final

    incomplete (but valid) character sequence.

    Does not check any bytes before the final sequence for correctness.

    >>> incomplete_utf8_sequence("")

    0

    >>> incomplete_utf8_sequence("xy")

    0

    >>> incomplete_utf8_sequence("xy\xc3\xbc")

    0

    >>> incomplete_utf8_sequence("\xc3")

    1

    >>> incomplete_utf8_sequence("\xbc\xc3")

    1

    >>> incomplete_utf8_sequence("xy\xbc\xc3")

    1

    >>> incomplete_utf8_sequence("xy\xe0\xa0")

    2

    >>> incomplete_utf8_sequence("xy\xf4")

    1

    >>> incomplete_utf8_sequence("xy\xf4\x8f")

    2

    >>> incomplete_utf8_sequence("xy\xf4\x8f\xa0")

    3

    """

    count = 0

    expect = None

    for b in byteseq[::-1]:

        b = ord(b)

        count += 1

        if b & 0x80 == 0x0:

            # 0xxxxxxx (single-byte character)

            expect = 1

            break

        elif b & 0xc0 == 0x80:

            # 10xxxxxx (subsequent byte)

            pass

        elif b & 0xe0 == 0xc0:

            # 110xxxxx (start of 2-byte sequence)

            expect = 2

            break

        elif b & 0xf0 == 0xe0:

            # 1110xxxx (start of 3-byte sequence)

            expect = 3

            break

        elif b & 0xf8 == 0xf0:

            # 11110xxx (start of 4-byte sequence)

            expect = 4

            break

        else:

            # Invalid byte

            return 0

        if count >= 4:

            # Seen too many "subsequent bytes", invalid

            return 0

    if expect is None:

        # We never saw a "first byte", invalid

        return 0

    # We now know expect and count

    if count >= expect:

        # Complete, or we saw an invalid sequence

        return 0

    elif count < expect:

        # Incomplete

        return count

def object_to_dict(attrnames, obj):

    """Convert an object into a dictionary.

    This takes a shallow copy of the object.

    @param attrnames: Set (or iterable) of names of attributes to be copied

                      into the dictionary. (We don't auto-lookup, because this

                      function needs to be used on magical objects).

    """

    return dict((k, getattr(obj, k))

        for k in attrnames if not k.startswith('_'))

def safe_rmtree(path, ignore_errors=False, onerror=None):

    """Recursively delete a directory tree.

    Copied from shutil.rmtree from Python 2.6, which does not follow symbolic

    links (it is otherwise unsafe to call as root on untrusted directories; do

    not use shutil.rmtree in this case, as you may be running Python 2.5).

    If ignore_errors is set, errors are ignored; otherwise, if onerror

    is set, it is called to handle the error with arguments (func,

    path, exc_info) where func is os.listdir, os.remove, or os.rmdir;

    path is the argument to that function that caused it to fail; and

    exc_info is a tuple returned by sys.exc_info().  If ignore_errors

    is false and onerror is None, an exception is raised.

    """

    if ignore_errors:

        def onerror(*args):

            pass

    elif onerror is None:

        def onerror(*args):

            raise

    try:

        if os.path.islink(path):

            # symlinks to directories are forbidden, see bug #1669

            raise OSError("Cannot call safe_rmtree on a symbolic link")

    except OSError:

        onerror(os.path.islink, path, sys.exc_info())

        # can't continue even if onerror hook returns

        return

    names = []

    try:

        names = os.listdir(path)

    except os.error, err:

        onerror(os.listdir, path, sys.exc_info())

    for name in names:

        fullname = os.path.join(path, name)

        try:

            mode = os.lstat(fullname).st_mode

        except os.error:

            mode = 0

        if stat.S_ISDIR(mode):

            safe_rmtree(fullname, ignore_errors, onerror)

        else:

            try:

                os.remove(fullname)

            except os.error, err:

                onerror(os.remove, fullname, sys.exc_info())

    try:

        os.rmdir(path)

    except os.error:

        onerror(os.rmdir, path, sys.exc_info())