78 lines
2.4 KiB
Python
78 lines
2.4 KiB
Python
#!/usr/bin/env python
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#
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# ASCII85/ASCIIHex decoder (Adobe version) implementation
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# * public domain *
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#
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# ascii85decode(data)
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def ascii85decode(data):
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import struct
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n = b = 0
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out = ''
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for c in data:
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if '!' <= c and c <= 'u':
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n += 1
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b = b*85+(ord(c)-33)
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if n == 5:
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out += struct.pack('>L',b)
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n = b = 0
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elif c == 'z':
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assert n == 0
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out += '\0\0\0\0'
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elif c == '~':
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if n:
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for _ in range(5-n):
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b = b*85+84
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out += struct.pack('>L',b)[:n-1]
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break
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return out
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# asciihexdecode(data)
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def asciihexdecode(data):
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"""
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ASCIIHexDecode filter: PDFReference v1.4 section 3.3.1
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For each pair of ASCII hexadecimal digits (0-9 and A-F or a-f), the
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ASCIIHexDecode filter produces one byte of binary data. All white-space
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characters are ignored. A right angle bracket character (>) indicates
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EOD. Any other characters will cause an error. If the filter encounters
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the EOD marker after reading an odd number of hexadecimal digits, it
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will behave as if a 0 followed the last digit.
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>>> asciihexdecode("61 62 2e6364 65")
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'ab.cde'
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>>> asciihexdecode("61 62 2e6364 657>")
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'ab.cdep'
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>>> asciihexdecode("7>")
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'p'
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"""
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import re
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hex_re = re.compile(r'([a-f\d]{2})', re.IGNORECASE)
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trail_re = re.compile(r'^(?:[a-f\d]{2}|\s)*([a-f\d])[\s>]*$', re.IGNORECASE)
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decode = (lambda hx: chr(int(hx, 16)))
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out = map(decode, hex_re.findall(data))
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m = trail_re.search(data)
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if m:
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out.append(decode("%c0" % m.group(1)))
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return ''.join(out)
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# test
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# sample taken from: http://en.wikipedia.org/w/index.php?title=Ascii85
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if __name__ == '__main__':
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orig = r'''
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9jqo^BlbD-BleB1DJ+*+F(f,q/0JhKF<GL>Cj@.4Gp$d7F!,L7@<6@)/0JDEF<G%<+EV:2F!,
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O<DJ+*.@<*K0@<6L(Df-\0Ec5e;DffZ(EZee.Bl.9pF"AGXBPCsi+DGm>@3BB/F*&OCAfu2/AKY
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i(DIb:@FD,*)+C]U=@3BN#EcYf8ATD3s@q?d$AftVqCh[NqF<G:8+EV:.+Cf>-FD5W8ARlolDIa
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l(DId<j@<?3r@:F%a+D58'ATD4$Bl@l3De:,-DJs`8ARoFb/0JMK@qB4^F!,R<AKZ&-DfTqBG%G
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>uD.RTpAKYo'+CT/5+Cei#DII?(E,9)oF*2M7/c~>
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'''
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data = \
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'Man is distinguished, not only by his reason, but by this singular passion from '\
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'other animals, which is a lust of the mind, that by a perseverance of delight in the '\
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'continued and indefatigable generation of knowledge, exceeds the short vehemence of '\
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'any carnal pleasure.'
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assert ascii85decode(orig) == data
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print 'ascii85decode test succeeded'
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import doctest
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doctest.testmod()
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