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https://github.com/elliotnunn/macresources.git
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ddfb909212
The GetEncoding function will allow macresources to cheaply and simply determine resource encoding without committing to a time-consuming extraction.
67 lines
1.8 KiB
Python
67 lines
1.8 KiB
Python
'''
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Handling of compressed MacOS resources.
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Author: Max Poliakovski 2018
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'''
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import struct
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from GreggBits import GreggDecompress, GreggCompress
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def GetEncoding(dat):
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sig, hdrlen, vers, attrs, biglen = struct.unpack_from(">IHBBI", dat)
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if sig != 0xA89F6572:
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print("Invalid extended resource header sig: 0x%X" % sig)
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return 'UnknownCompression'
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if vers not in (8, 9):
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print("Unknown ext res header format: %d" % vers)
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return 'UnknownCompression'
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if attrs & 1 == 0:
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print("extAttributes,bit0 isn't set. Treat this res as uncompressed.")
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return 'UnknownCompression'
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print("Uncompressed length: %d" % biglen)
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if vers == 8:
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print('Donn unimplemented!'); return 'UnknownCompression'
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return 'DonnBits'
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elif vers == 9:
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if dat[12:14] == b'\x00\x02':
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return 'GreggyBits'
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else:
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return 'UnknownCompression'
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else:
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return 'UnknownCompression'
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def DecompressResource(dat):
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encoding = GetEncoding(dat)
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sig, hdrlen, vers, attrs, biglen = struct.unpack_from(">IHBBI", dat)
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if encoding == 'DonnBits':
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raise NotImplementedError('DonnBits')
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elif encoding == 'GreggyBits':
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dst = bytearray()
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GreggDecompress(dat, dst, unpackSize=biglen, pos=12)
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return bytes(dst)
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elif encoding == 'UnknownCompression':
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return dat # passthru
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def CompressResource(dat, encoding):
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if encoding == 'UnknownCompression':
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return dat
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elif encoding == 'GreggyBits':
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dst = bytearray()
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# re-create extended resource header
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dst.extend([0xA8, 0x9F, 0x65, 0x72, 0x00, 0x12, 0x09, 0x01])
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dst.extend(len(dat).to_bytes(4, 'big'))
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# leave Gregg-specific header to the compressor
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GreggCompress(dat, dst)
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return bytes(dst)
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