OwlCyberSecurity - MANAGER

Edit File: type1font.py

"""
This module contains a class representing a Type 1 font.

This version reads pfa and pfb files and splits them for embedding in
pdf files. It also supports SlantFont and ExtendFont transformations,
similarly to pdfTeX and friends. There is no support yet for
subsetting.

Usage::

>>> font = Type1Font(filename)
   >>> clear_part, encrypted_part, finale = font.parts
   >>> slanted_font = font.transform({'slant': 0.167})
   >>> extended_font = font.transform({'extend': 1.2})

Sources:

* Adobe Technical Note #5040, Supporting Downloadable PostScript
  Language Fonts.

* Adobe Type 1 Font Format, Adobe Systems Incorporated, third printing,
  v1.1, 1993. ISBN 0-201-57044-0.
"""

import binascii
import enum
import itertools
import re
import struct

import numpy as np

# token types
_TokenType = enum.Enum('_TokenType',
                       'whitespace name string delimiter number')

class Type1Font(object):
    """
    A class representing a Type-1 font, for use by backends.

Attributes
    ----------
    parts : tuple
        A 3-tuple of the cleartext part, the encrypted part, and the finale of
        zeros.

prop : Dict[str, Any]
        A dictionary of font properties.

"""
    __slots__ = ('parts', 'prop')

def __init__(self, input):
        """
        Initialize a Type-1 font. *input* can be either the file name of
        a pfb file or a 3-tuple of already-decoded Type-1 font parts.
        """
        if isinstance(input, tuple) and len(input) == 3:
            self.parts = input
        else:
            with open(input, 'rb') as file:
                data = self._read(file)
            self.parts = self._split(data)

self._parse()

def _read(self, file):
        """
        Read the font from a file, decoding into usable parts.
        """
        rawdata = file.read()
        if not rawdata.startswith(b'\x80'):
            return rawdata

data = b''
        while rawdata:
            if not rawdata.startswith(b'\x80'):
                raise RuntimeError('Broken pfb file (expected byte 128, '
                                   'got %d)' % rawdata[0])
            type = rawdata[1]
            if type in (1, 2):
                length, = struct.unpack('<i', rawdata[2:6])
                segment = rawdata[6:6 + length]
                rawdata = rawdata[6 + length:]

if type == 1:       # ASCII text: include verbatim
                data += segment
            elif type == 2:     # binary data: encode in hexadecimal
                data += binascii.hexlify(segment)
            elif type == 3:     # end of file
                break
            else:
                raise RuntimeError('Unknown segment type %d in pfb file' %
                                   type)

return data

def _split(self, data):
        """
        Split the Type 1 font into its three main parts.

The three parts are: (1) the cleartext part, which ends in a
        eexec operator; (2) the encrypted part; (3) the fixed part,
        which contains 512 ASCII zeros possibly divided on various
        lines, a cleartomark operator, and possibly something else.
        """

# Cleartext part: just find the eexec and skip whitespace
        idx = data.index(b'eexec')
        idx += len(b'eexec')
        while data[idx] in b' \t\r\n':
            idx += 1
        len1 = idx

# Encrypted part: find the cleartomark operator and count
        # zeros backward
        idx = data.rindex(b'cleartomark') - 1
        zeros = 512
        while zeros and data[idx] in b'0' or data[idx] in b'\r\n':
            if data[idx] in b'0':
                zeros -= 1
            idx -= 1
        if zeros:
            raise RuntimeError('Insufficiently many zeros in Type 1 font')

# Convert encrypted part to binary (if we read a pfb file, we may end
        # up converting binary to hexadecimal to binary again; but if we read
        # a pfa file, this part is already in hex, and I am not quite sure if
        # even the pfb format guarantees that it will be in binary).
        binary = binascii.unhexlify(data[len1:idx+1])

return data[:len1], binary, data[idx+1:]

_whitespace_re = re.compile(br'[\0\t\r\014\n ]+')
    _token_re = re.compile(br'/{0,2}[^]\0\t\r\v\n ()<>{}/%[]+')
    _comment_re = re.compile(br'%[^\r\n\v]*')
    _instring_re = re.compile(br'[()\\]')

@classmethod
    def _tokens(cls, text):
        """
        A PostScript tokenizer. Yield (token, value) pairs such as
        (_TokenType.whitespace, '   ') or (_TokenType.name, '/Foobar').
        """
        pos = 0
        while pos < len(text):
            match = (cls._comment_re.match(text[pos:]) or
                     cls._whitespace_re.match(text[pos:]))
            if match:
                yield (_TokenType.whitespace, match.group())
                pos += match.end()
            elif text[pos] == b'(':
                start = pos
                pos += 1
                depth = 1
                while depth:
                    match = cls._instring_re.search(text[pos:])
                    if match is None:
                        return
                    pos += match.end()
                    if match.group() == b'(':
                        depth += 1
                    elif match.group() == b')':
                        depth -= 1
                    else:  # a backslash - skip the next character
                        pos += 1
                yield (_TokenType.string, text[start:pos])
            elif text[pos:pos + 2] in (b'<<', b'>>'):
                yield (_TokenType.delimiter, text[pos:pos + 2])
                pos += 2
            elif text[pos] == b'<':
                start = pos
                pos += text[pos:].index(b'>')
                yield (_TokenType.string, text[start:pos])
            else:
                match = cls._token_re.match(text[pos:])
                if match:
                    try:
                        float(match.group())
                        yield (_TokenType.number, match.group())
                    except ValueError:
                        yield (_TokenType.name, match.group())
                    pos += match.end()
                else:
                    yield (_TokenType.delimiter, text[pos:pos + 1])
                    pos += 1

def _parse(self):
        """
        Find the values of various font properties. This limited kind
        of parsing is described in Chapter 10 "Adobe Type Manager
        Compatibility" of the Type-1 spec.
        """
        # Start with reasonable defaults
        prop = {'weight': 'Regular', 'ItalicAngle': 0.0, 'isFixedPitch': False,
                'UnderlinePosition': -100, 'UnderlineThickness': 50}
        filtered = ((token, value)
                    for token, value in self._tokens(self.parts[0])
                    if token is not _TokenType.whitespace)
        # The spec calls this an ASCII format; in Python 2.x we could
        # just treat the strings and names as opaque bytes but let's
        # turn them into proper Unicode, and be lenient in case of high bytes.
        convert = lambda x: x.decode('ascii', 'replace')
        for token, value in filtered:
            if token is _TokenType.name and value.startswith(b'/'):
                key = convert(value[1:])
                token, value = next(filtered)
                if token is _TokenType.name:
                    if value in (b'true', b'false'):
                        value = value == b'true'
                    else:
                        value = convert(value.lstrip(b'/'))
                elif token is _TokenType.string:
                    value = convert(value.lstrip(b'(').rstrip(b')'))
                elif token is _TokenType.number:
                    if b'.' in value:
                        value = float(value)
                    else:
                        value = int(value)
                else:  # more complicated value such as an array
                    value = None
                if key != 'FontInfo' and value is not None:
                    prop[key] = value

# Fill in the various *Name properties
        if 'FontName' not in prop:
            prop['FontName'] = (prop.get('FullName') or
                                prop.get('FamilyName') or
                                'Unknown')
        if 'FullName' not in prop:
            prop['FullName'] = prop['FontName']
        if 'FamilyName' not in prop:
            extras = ('(?i)([ -](regular|plain|italic|oblique|(semi)?bold|'
                      '(ultra)?light|extra|condensed))+$')
            prop['FamilyName'] = re.sub(extras, '', prop['FullName'])

self.prop = prop

@classmethod
    def _transformer(cls, tokens, slant, extend):
        def fontname(name):
            result = name
            if slant:
                result += b'_Slant_%d' % int(1000 * slant)
            if extend != 1.0:
                result += b'_Extend_%d' % int(1000 * extend)
            return result

def italicangle(angle):
            return b'%a' % (float(angle) - np.arctan(slant) / np.pi * 180)

def fontmatrix(array):
            array = array.lstrip(b'[').rstrip(b']').split()
            array = [float(x) for x in array]
            oldmatrix = np.eye(3, 3)
            oldmatrix[0:3, 0] = array[::2]
            oldmatrix[0:3, 1] = array[1::2]
            modifier = np.array([[extend, 0, 0],
                                 [slant, 1, 0],
                                 [0, 0, 1]])
            newmatrix = np.dot(modifier, oldmatrix)
            array[::2] = newmatrix[0:3, 0]
            array[1::2] = newmatrix[0:3, 1]
            # Not directly using `b'%a' % x for x in array` for now as that
            # produces longer reprs on numpy<1.14, causing test failures.
            as_string = '[' + ' '.join(str(x) for x in array) + ']'
            return as_string.encode('latin-1')

def replace(fun):
            def replacer(tokens):
                token, value = next(tokens)      # name, e.g., /FontMatrix
                yield value
                token, value = next(tokens)      # possible whitespace
                while token is _TokenType.whitespace:
                    yield value
                    token, value = next(tokens)
                if value != b'[':                # name/number/etc.
                    yield fun(value)
                else:                            # array, e.g., [1 2 3]
                    result = b''
                    while value != b']':
                        result += value
                        token, value = next(tokens)
                    result += value
                    yield fun(result)
            return replacer

def suppress(tokens):
            for x in itertools.takewhile(lambda x: x[1] != b'def', tokens):
                pass
            yield b''

table = {b'/FontName': replace(fontname),
                 b'/ItalicAngle': replace(italicangle),
                 b'/FontMatrix': replace(fontmatrix),
                 b'/UniqueID': suppress}

for token, value in tokens:
            if token is _TokenType.name and value in table:
                yield from table[value](
                    itertools.chain([(token, value)], tokens))
            else:
                yield value

def transform(self, effects):
        """
        Transform the font by slanting or extending. *effects* should
        be a dict where ``effects['slant']`` is the tangent of the
        angle that the font is to be slanted to the right (so negative
        values slant to the left) and ``effects['extend']`` is the
        multiplier by which the font is to be extended (so values less
        than 1.0 condense). Returns a new :class:`Type1Font` object.
        """
        tokenizer = self._tokens(self.parts[0])
        transformed = self._transformer(tokenizer,
                                        slant=effects.get('slant', 0.0),
                                        extend=effects.get('extend', 1.0))
        return Type1Font((b"".join(transformed), self.parts[1], self.parts[2]))