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24 lines
992 B
Python
24 lines
992 B
Python
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import typing
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class DecompressError(Exception):
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"""Raised when resource data decompression fails, because the data is invalid or the compression type is not supported."""
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def _read_variable_length_integer(data: bytes, position: int) -> typing.Tuple[int, int]:
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"""Read a variable-length integer starting at the given position in the data, and return the integer as well as the number of bytes consumed.
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This variable-length integer format is used by the 0xfe codes in the compression formats used by 'dcmp' (0) and 'dcmp' (1).
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"""
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assert len(data) > position
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if data[position] == 0xff:
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assert len(data) > position + 4
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return int.from_bytes(data[position+1:position+5], "big", signed=True), 5
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elif data[position] >= 0x80:
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assert len(data) > position + 1
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data_modified = bytes([(data[position] - 0xc0) & 0xff, data[position+1]])
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return int.from_bytes(data_modified, "big", signed=True), 2
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else:
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return int.from_bytes(data[position:position+1], "big", signed=True), 1
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