gsm0338.py

# 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 Street, Fifth Floor, Boston, MA 02110-1301 USA.

import codecs
import sys
import traceback

# data from
# http://snoops.roy202.org/testerman/browser/trunk/plugins/codecs/gsm0338.py

# default GSM 03.38 -> unicode
def_regular_decode_dict = {
    '\x00': u'\u0040',  # COMMERCIAL AT
    '\x01': u'\u00A3',  # POUND SIGN
    '\x02': u'\u0024',  # DOLLAR SIGN
    '\x03': u'\u00A5',  # YEN SIGN
    '\x04': u'\u00E8',  # LATIN SMALL LETTER E WITH GRAVE
    '\x05': u'\u00E9',  # LATIN SMALL LETTER E WITH ACUTE
    '\x06': u'\u00F9',  # LATIN SMALL LETTER U WITH GRAVE
    '\x07': u'\u00EC',  # LATIN SMALL LETTER I WITH GRAVE
    '\x08': u'\u00F2',  # LATIN SMALL LETTER O WITH GRAVE
    '\x09': u'\u00C7',  # LATIN CAPITAL LETTER C WITH CEDILLA
                        # The Unicode page suggests this is a mistake: but
                        # it's still in the latest version of the spec and
                        # our implementation has to be exact.

    '\x0A': u'\u000A',  # LINE FEED
    '\x0B': u'\u00D8',  # LATIN CAPITAL LETTER O WITH STROKE
    '\x0C': u'\u00F8',  # LATIN SMALL LETTER O WITH STROKE
    '\x0D': u'\u000D',  # CARRIAGE RETURN
    '\x0E': u'\u00C5',  # LATIN CAPITAL LETTER A WITH RING ABOVE
    '\x0F': u'\u00E5',  # LATIN SMALL LETTER A WITH RING ABOVE
    '\x10': u'\u0394',  # GREEK CAPITAL LETTER DELTA
    '\x11': u'\u005F',  # LOW LINE
    '\x12': u'\u03A6',  # GREEK CAPITAL LETTER PHI
    '\x13': u'\u0393',  # GREEK CAPITAL LETTER GAMMA
    '\x14': u'\u039B',  # GREEK CAPITAL LETTER LAMDA
    '\x15': u'\u03A9',  # GREEK CAPITAL LETTER OMEGA
    '\x16': u'\u03A0',  # GREEK CAPITAL LETTER PI
    '\x17': u'\u03A8',  # GREEK CAPITAL LETTER PSI
    '\x18': u'\u03A3',  # GREEK CAPITAL LETTER SIGMA
    '\x19': u'\u0398',  # GREEK CAPITAL LETTER THETA
    '\x1A': u'\u039E',  # GREEK CAPITAL LETTER XI
    '\x1C': u'\u00C6',  # LATIN CAPITAL LETTER AE
    '\x1D': u'\u00E6',  # LATIN SMALL LETTER AE
    '\x1E': u'\u00DF',  # LATIN SMALL LETTER SHARP S (German)
    '\x1F': u'\u00C9',  # LATIN CAPITAL LETTER E WITH ACUTE
    '\x20': u'\u0020',  # SPACE
    '\x21': u'\u0021',  # EXCLAMATION MARK
    '\x22': u'\u0022',  # QUOTATION MARK
    '\x23': u'\u0023',  # NUMBER SIGN
    '\x24': u'\u00A4',  # CURRENCY SIGN
    '\x25': u'\u0025',  # PERCENT SIGN
    '\x26': u'\u0026',  # AMPERSAND
    '\x27': u'\u0027',  # APOSTROPHE
    '\x28': u'\u0028',  # LEFT PARENTHESIS
    '\x29': u'\u0029',  # RIGHT PARENTHESIS
    '\x2A': u'\u002A',  # ASTERISK
    '\x2B': u'\u002B',  # PLUS SIGN
    '\x2C': u'\u002C',  # COMMA
    '\x2D': u'\u002D',  # HYPHEN-MINUS
    '\x2E': u'\u002E',  # FULL STOP
    '\x2F': u'\u002F',  # SOLIDUS
    '\x30': u'\u0030',  # DIGIT ZERO
    '\x31': u'\u0031',  # DIGIT ONE
    '\x32': u'\u0032',  # DIGIT TWO
    '\x33': u'\u0033',  # DIGIT THREE
    '\x34': u'\u0034',  # DIGIT FOUR
    '\x35': u'\u0035',  # DIGIT FIVE
    '\x36': u'\u0036',  # DIGIT SIX
    '\x37': u'\u0037',  # DIGIT SEVEN
    '\x38': u'\u0038',  # DIGIT EIGHT
    '\x39': u'\u0039',  # DIGIT NINE
    '\x3A': u'\u003A',  # COLON
    '\x3B': u'\u003B',  # SEMICOLON
    '\x3C': u'\u003C',  # LESS-THAN SIGN
    '\x3D': u'\u003D',  # EQUALS SIGN
    '\x3E': u'\u003E',  # GREATER-THAN SIGN
    '\x3F': u'\u003F',  # QUESTION MARK
    '\x40': u'\u00A1',  # INVERTED EXCLAMATION MARK
    '\x41': u'\u0041',  # LATIN CAPITAL LETTER A
    '\x42': u'\u0042',  # LATIN CAPITAL LETTER B
    '\x43': u'\u0043',  # LATIN CAPITAL LETTER C
    '\x44': u'\u0044',  # LATIN CAPITAL LETTER D
    '\x45': u'\u0045',  # LATIN CAPITAL LETTER E
    '\x46': u'\u0046',  # LATIN CAPITAL LETTER F
    '\x47': u'\u0047',  # LATIN CAPITAL LETTER G
    '\x48': u'\u0048',  # LATIN CAPITAL LETTER H
    '\x49': u'\u0049',  # LATIN CAPITAL LETTER I
    '\x4A': u'\u004A',  # LATIN CAPITAL LETTER J
    '\x4B': u'\u004B',  # LATIN CAPITAL LETTER K
    '\x4C': u'\u004C',  # LATIN CAPITAL LETTER L
    '\x4D': u'\u004D',  # LATIN CAPITAL LETTER M
    '\x4E': u'\u004E',  # LATIN CAPITAL LETTER N
    '\x4F': u'\u004F',  # LATIN CAPITAL LETTER O
    '\x50': u'\u0050',  # LATIN CAPITAL LETTER P
    '\x51': u'\u0051',  # LATIN CAPITAL LETTER Q
    '\x52': u'\u0052',  # LATIN CAPITAL LETTER R
    '\x53': u'\u0053',  # LATIN CAPITAL LETTER S
    '\x54': u'\u0054',  # LATIN CAPITAL LETTER T
    '\x55': u'\u0055',  # LATIN CAPITAL LETTER U
    '\x56': u'\u0056',  # LATIN CAPITAL LETTER V
    '\x57': u'\u0057',  # LATIN CAPITAL LETTER W
    '\x58': u'\u0058',  # LATIN CAPITAL LETTER X
    '\x59': u'\u0059',  # LATIN CAPITAL LETTER Y
    '\x5A': u'\u005A',  # LATIN CAPITAL LETTER Z
    '\x5B': u'\u00C4',  # LATIN CAPITAL LETTER A WITH DIAERESIS
    '\x5C': u'\u00D6',  # LATIN CAPITAL LETTER O WITH DIAERESIS
    '\x5D': u'\u00D1',  # LATIN CAPITAL LETTER N WITH TILDE
    '\x5E': u'\u00DC',  # LATIN CAPITAL LETTER U WITH DIAERESIS
    '\x5F': u'\u00A7',  # SECTION SIGN
    '\x60': u'\u00BF',  # INVERTED QUESTION MARK
    '\x61': u'\u0061',  # LATIN SMALL LETTER A
    '\x62': u'\u0062',  # LATIN SMALL LETTER B
    '\x63': u'\u0063',  # LATIN SMALL LETTER C
    '\x64': u'\u0064',  # LATIN SMALL LETTER D
    '\x65': u'\u0065',  # LATIN SMALL LETTER E
    '\x66': u'\u0066',  # LATIN SMALL LETTER F
    '\x67': u'\u0067',  # LATIN SMALL LETTER G
    '\x68': u'\u0068',  # LATIN SMALL LETTER H
    '\x69': u'\u0069',  # LATIN SMALL LETTER I
    '\x6A': u'\u006A',  # LATIN SMALL LETTER J
    '\x6B': u'\u006B',  # LATIN SMALL LETTER K
    '\x6C': u'\u006C',  # LATIN SMALL LETTER L
    '\x6D': u'\u006D',  # LATIN SMALL LETTER M
    '\x6E': u'\u006E',  # LATIN SMALL LETTER N
    '\x6F': u'\u006F',  # LATIN SMALL LETTER O
    '\x70': u'\u0070',  # LATIN SMALL LETTER P
    '\x71': u'\u0071',  # LATIN SMALL LETTER Q
    '\x72': u'\u0072',  # LATIN SMALL LETTER R
    '\x73': u'\u0073',  # LATIN SMALL LETTER S
    '\x74': u'\u0074',  # LATIN SMALL LETTER T
    '\x75': u'\u0075',  # LATIN SMALL LETTER U
    '\x76': u'\u0076',  # LATIN SMALL LETTER V
    '\x77': u'\u0077',  # LATIN SMALL LETTER W
    '\x78': u'\u0078',  # LATIN SMALL LETTER X
    '\x79': u'\u0079',  # LATIN SMALL LETTER Y
    '\x7A': u'\u007A',  # LATIN SMALL LETTER Z
    '\x7B': u'\u00E4',  # LATIN SMALL LETTER A WITH DIAERESIS
    '\x7C': u'\u00F6',  # LATIN SMALL LETTER O WITH DIAERESIS
    '\x7D': u'\u00F1',  # LATIN SMALL LETTER N WITH TILDE
    '\x7E': u'\u00FC',  # LATIN SMALL LETTER U WITH DIAERESIS
    '\x7F': u'\u00E0',  # LATIN SMALL LETTER A WITH GRAVE
}

# default GSM 03.38 escaped characters -> unicode
def_escape_decode_dict = {
    '\x0A': u'\u000C',  # FORM FEED
    '\x14': u'\u005E',  # CIRCUMFLEX ACCENT
    '\x28': u'\u007B',  # LEFT CURLY BRACKET
    '\x29': u'\u007D',  # RIGHT CURLY BRACKET
    '\x2F': u'\u005C',  # REVERSE SOLIDUS
    '\x3C': u'\u005B',  # LEFT SQUARE BRACKET
    '\x3D': u'\u007E',  # TILDE
    '\x3E': u'\u005D',  # RIGHT SQUARE BRACKET
    '\x40': u'\u007C',  # VERTICAL LINE
    '\x65': u'\u20AC',  # EURO SIGN
}

# Replacement characters, default is question mark. Used when it is not too
# important to ensure exact UTF-8 -> GSM -> UTF-8 equivilence, such as when
# humans read and write SMS. But for USSD and other M2M applications it's
# important to ensure the conversion is exact.
def_replace_encode_dict = {
    u'\u00E7': '\x09',  # LATIN SMALL LETTER C WITH CEDILLA

    u'\u0391': '\x41',  # GREEK CAPITAL LETTER ALPHA
    u'\u0392': '\x42',  # GREEK CAPITAL LETTER BETA
    u'\u0395': '\x45',  # GREEK CAPITAL LETTER EPSILON
    u'\u0397': '\x48',  # GREEK CAPITAL LETTER ETA
    u'\u0399': '\x49',  # GREEK CAPITAL LETTER IOTA
    u'\u039A': '\x4B',  # GREEK CAPITAL LETTER KAPPA
    u'\u039C': '\x4D',  # GREEK CAPITAL LETTER MU
    u'\u039D': '\x4E',  # GREEK CAPITAL LETTER NU
    u'\u039F': '\x4F',  # GREEK CAPITAL LETTER OMICRON
    u'\u03A1': '\x50',  # GREEK CAPITAL LETTER RHO
    u'\u03A4': '\x54',  # GREEK CAPITAL LETTER TAU
    u'\u03A7': '\x58',  # GREEK CAPITAL LETTER CHI
    u'\u03A5': '\x59',  # GREEK CAPITAL LETTER UPSILON
    u'\u0396': '\x5A',  # GREEK CAPITAL LETTER ZETA
}

QUESTION_MARK = chr(0x3f)

# unicode -> default GSM 03.38
def_regular_encode_dict = \
    dict((u, g) for g, u in def_regular_decode_dict.iteritems())

# unicode -> default escaped GSM 03.38 characters
def_escape_encode_dict = \
    dict((u, g) for g, u in def_escape_decode_dict.iteritems())


def encode(input_, errors='strict'):
    """
    :type input_: unicode

    :return: string
    """
    result = []
    for c in input_:
        try:
            result.append(def_regular_encode_dict[c])
        except KeyError:
            if c in def_escape_encode_dict:
                # OK, let's encode it as an escaped characters
                result.append('\x1b')
                result.append(def_escape_encode_dict[c])
            else:
                if errors == 'strict':
                    raise UnicodeError("Invalid GSM character")
                elif errors == 'replace':
                    result.append(
                                def_replace_encode_dict.get(c, QUESTION_MARK))
                elif errors == 'ignore':
                    pass
                else:
                    raise UnicodeError("Unknown error handling")

    ret = ''.join(result)
    return ret, len(ret)


def decode(input_, errors='strict'):
    """
    :type input_: str

    :return: unicode
    """
    result = []
    index = 0
    while index < len(input_):
        c = input_[index]
        index += 1
        if c == '\x1b':
            if index < len(input_):
                c = input_[index]
                index += 1
                result.append(def_escape_decode_dict.get(c, u'\xa0'))
            else:
                result.append(u'\xa0')
        else:
            try:
                result.append(def_regular_decode_dict[c])
            except KeyError:
                # error handling: unassigned byte, must be > 0x7f
                if errors == 'strict':
                    raise UnicodeError("Unrecognized GSM character")
                elif errors == 'replace':
                    result.append('?')
                elif errors == 'ignore':
                    pass
                else:
                    raise UnicodeError("Unknown error handling")

    ret = u''.join(result)
    return ret, len(ret)


# encodings module API
def getregentry(encoding):
    if encoding == 'gsm0338':
        return codecs.CodecInfo(name='gsm0338',
                                encode=encode,
                                decode=decode)

# Codec registration
codecs.register(getregentry)


def is_gsm_text(text):
    """Returns True if ``text`` can be encoded as gsm text"""
    try:
        text.encode("gsm0338")
    except UnicodeError:
        return False
    except:
        traceback.print_exc(file=sys.stdout)
        return False

    return True