42 lines
1.4 KiB
Python
42 lines
1.4 KiB
Python
"""Python implementation of ASCII85/ASCIIHex decoder (Adobe version)."""
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import re
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from base64 import a85decode
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from binascii import unhexlify
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def ascii85decode(data: bytes) -> bytes:
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"""In ASCII85 encoding, every four bytes are encoded with five ASCII
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letters, using 85 different types of characters (as 256**4 < 85**5).
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When the length of the original bytes is not a multiple of 4, a special
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rule is used for round up.
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The Adobe's ASCII85 implementation is slightly different from
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its original in handling the last characters.
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"""
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try:
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return a85decode(data, adobe=True)
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except ValueError:
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return a85decode(data)
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bws_re = re.compile(rb"\s")
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def asciihexdecode(data: bytes) -> bytes:
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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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"""
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data = bws_re.sub(b"", data)
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idx = data.find(b">")
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if idx != -1:
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data = data[:idx]
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if idx % 2 == 1:
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data += b"0"
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return unhexlify(data)
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