root/imapclient/imap_utf7.py

# The contents of this file has been derived code from the Twisted project
# (http://twistedmatrix.com/). The original author is Jp Calderone.

# Twisted project license follows:

# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
# 
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


class FolderNameError(ValueError):
    pass


def encode(s):
    if isinstance(s, str) and sum(n for n in (ord(c) for c in s) if n > 127):
        raise FolderNameError("%r contains characters not valid in a str folder name. "
                              "Convert to unicode first?" % s)

    r = []
    _in = []
    for c in s:
        if ord(c) in (range(0x20, 0x26) + range(0x27, 0x7f)):
            if _in:
                r.extend(['&', modified_base64(''.join(_in)), '-'])
                del _in[:]
            r.append(str(c))
        elif c == '&':
            if _in:
                r.extend(['&', modified_base64(''.join(_in)), '-'])
                del _in[:]
            r.append('&-')
        else:
            _in.append(c)
    if _in:
        r.extend(['&', modified_base64(''.join(_in)), '-'])
    return ''.join(r)


def decode(s):
    r = []
    decode = []
    for c in s:
        if c == '&' and not decode:
            decode.append('&')
        elif c == '-' and decode:
            if len(decode) == 1:
                r.append('&')
            else:
                r.append(modified_unbase64(''.join(decode[1:])))
            decode = []
        elif decode:
            decode.append(c)
        else:
            r.append(c)
    if decode:
        r.append(modified_unbase64(''.join(decode[1:])))
    out = ''.join(r)

    if not isinstance(out, unicode):
        out = unicode(out, 'latin-1')
    return out


def modified_base64(s):
    s_utf7 = s.encode('utf-7')
    return s_utf7[1:-1].replace('/', ',')


def modified_unbase64(s):
    s_utf7 = '+' + s.replace(',', '/') + '-'
    return s_utf7.decode('utf-7')