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https://github.com/dgelessus/python-rsrcfork.git
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f3b3de496e
The old names ("system" and "application" compression) were not really
accurate in all cases, so the compression types are now referred to by
their number.
270 lines
11 KiB
Python
270 lines
11 KiB
Python
import io
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import typing
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from . import common
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# Lookup table for codes in range(0x4b, 0xfe).
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# This table was obtained by decompressing a manually created compressed resource with the following contents:
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# b'\xa8\x9fer\x00\x12\x08\x01\x00\x00\x01f\x80\x03\x00\x00\x00\x00' + bytes(range(0x4b, 0xfe)) + b'\xff'
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TABLE_DATA = (
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# First line corresponds to codes in range(0x4b, 0x50).
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b"\x00\x00N\xba\x00\x08Nu\x00\x0c"
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# All following lines correspond to 8 codes each.
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b"N\xad S/\x0ba\x00\x00\x10p\x00/\x00Hn"
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b" P n/.\xff\xfcH\xe7?<\x00\x04\xff\xf8"
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b"/\x0c \x06N\xedNV hN^\x00\x01X\x8f"
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b"O\xef\x00\x02\x00\x18`\x00\xff\xffP\x8fN\x90\x00\x06"
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b"&n\x00\x14\xff\xf4L\xee\x00\n\x00\x0eA\xeeL\xdf"
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b"H\xc0\xff\xf0-@\x00\x120.p\x01/( T"
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b"g\x00\x00 \x00\x1c _\x18\x00&oHx\x00\x16"
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b"A\xfa0<(@r\x00(n \x0cf\x00 k"
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b"/\x07U\x8f\x00(\xff\xfe\xff\xec\"\xd8 \x0b\x00\x0f"
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b"Y\x8f/<\xff\x00\x01\x18\x81\xe1J\x00N\xb0\xff\xe8"
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b"H\xc7\x00\x03\x00\"\x00\x07\x00\x1ag\x06g\x08N\xf9"
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b"\x00$ x\x08\x00f\x04\x00*N\xd00(&_"
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b"g\x04\x000C\xee?\x00 \x1f\x00\x1e\xff\xf6 ."
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b"B\xa7 \x07\xff\xfa`\x02=@\x0c@f\x06\x00&"
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b"-H/\x01p\xff`\x04\x18\x80J@\x00@\x00,"
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b"/\x08\x00\x11\xff\xe4!@&@\xff\xf2BnN\xb9"
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b"=|\x008\x00\r`\x06B. <g\x0c-h"
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b"f\x08J.J\xae\x00.H@\"_\"\x00g\n"
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b"0\x07Bg\x002 (\x00\tHz\x02\x00/+"
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b"\x00\x05\"nf\x02\xe5\x80g\x0ef\n\x00P>\x00"
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b"f\x0c.\x00\xff\xee m @\xff\xe0S@`\x08"
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# Last line corresponds to codes in range(0xf8, 0xfe).
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b"\x04\x80\x00h\x0b|D\x00A\xe8HA"
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)
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# Note: index 0 in this table corresponds to code 0x4b, index 1 to 0x4c, etc.
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TABLE = [TABLE_DATA[i:i + 2] for i in range(0, len(TABLE_DATA), 2)]
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assert len(TABLE) == len(range(0x4b, 0xfe))
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def decompress_stream_inner(header_info: common.CompressedHeaderInfo, stream: typing.BinaryIO, *, debug: bool=False) -> typing.Iterator[bytes]:
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"""Internal helper function, implements the main decompression algorithm. Only called from decompress_stream, which performs some extra checks and debug logging."""
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if not isinstance(header_info, common.CompressedType8HeaderInfo):
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raise common.DecompressError(f"Incorrect header type: {type(header_info).__qualname__}")
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prev_literals: typing.List[bytes] = []
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while True: # Loop is terminated when the EOF marker (0xff) is encountered
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(byte,) = common.read_exact(stream, 1)
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if debug:
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print(f"Tag byte 0x{byte:>02x}")
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if byte in range(0x00, 0x20):
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# Literal byte sequence.
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if byte in (0x00, 0x10):
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# The length of the literal data is stored in the next byte.
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(count_div2,) = common.read_exact(stream, 1)
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else:
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# The length of the literal data is stored in the low nibble of the tag byte.
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count_div2 = byte >> 0 & 0xf
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count = 2 * count_div2
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# Controls whether or not the literal is stored so that it can be referenced again later.
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do_store = byte >= 0x10
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literal = common.read_exact(stream, count)
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if debug:
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print(f"Literal (storing: {do_store})")
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if do_store:
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if debug:
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print(f"\t-> storing as literal number 0x{len(prev_literals):x}")
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prev_literals.append(literal)
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yield literal
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elif byte in (0x20, 0x21):
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# Backreference to a previous literal, 2-byte form.
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# This can reference literals with index in range(0x28, 0x228).
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(next_byte,) = common.read_exact(stream, 1)
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table_index = 0x28 + ((byte - 0x20) << 8 | next_byte)
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if debug:
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print(f"Backreference (2-byte form) to 0x{table_index:>02x}")
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yield prev_literals[table_index]
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elif byte == 0x22:
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# Backreference to a previous literal, 3-byte form.
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# This can reference any literal with index 0x28 and higher, but is only necessary for literals with index 0x228 and higher.
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table_index = 0x28 + int.from_bytes(common.read_exact(stream, 2), "big", signed=False)
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if debug:
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print(f"Backreference (3-byte form) to 0x{table_index:>02x}")
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yield prev_literals[table_index]
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elif byte in range(0x23, 0x4b):
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# Backreference to a previous literal, 1-byte form.
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# This can reference literals with indices in range(0x28).
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table_index = byte - 0x23
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if debug:
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print(f"Backreference (1-byte form) to 0x{table_index:>02x}")
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yield prev_literals[table_index]
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elif byte in range(0x4b, 0xfe):
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# Reference into a fixed table of two-byte literals.
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# All compressed resources use the same table.
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table_index = byte - 0x4b
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if debug:
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print(f"Fixed table reference to 0x{table_index:>02x}")
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yield TABLE[table_index]
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elif byte == 0xfe:
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# Extended code, whose meaning is controlled by the following byte.
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(kind,) = common.read_exact(stream, 1)
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if debug:
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print(f"Extended code: 0x{kind:>02x}")
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if kind == 0x00:
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# Compact representation of (part of) a segment loader jump table, as used in 'CODE' (0) resources.
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if debug:
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print(f"Segment loader jump table entries")
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# All generated jump table entries have the same segment number.
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segment_number_int = common.read_variable_length_integer(stream)
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if debug:
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print(f"\t-> segment number: {segment_number_int:#x}")
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# The tail part of all jump table entries (i. e. everything except for the address).
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entry_tail = b"?<" + segment_number_int.to_bytes(2, "big", signed=True) + b"\xa9\xf0"
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# The tail is output once *without* an address in front, i. e. the first entry's address must be generated manually by a previous code.
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yield entry_tail
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count = common.read_variable_length_integer(stream)
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if count <= 0:
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raise common.DecompressError(f"Jump table entry count must be greater than 0, not {count}")
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# The second entry's address is stored explicitly.
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current_int = common.read_variable_length_integer(stream)
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if debug:
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print(f"\t-> address of second entry: {current_int:#x}")
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yield current_int.to_bytes(2, "big", signed=False) + entry_tail
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for _ in range(1, count):
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# All further entries' addresses are stored as differences relative to the previous entry's address.
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diff = common.read_variable_length_integer(stream)
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# For some reason, each difference is 6 higher than it should be.
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diff -= 6
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# Simulate 16-bit integer wraparound.
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current_int = (current_int + diff) & 0xffff
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if debug:
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print(f"\t-> difference {diff:#x}: {current_int:#x}")
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yield current_int.to_bytes(2, "big", signed=False) + entry_tail
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elif kind in (0x02, 0x03):
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# Repeat 1 or 2 bytes a certain number of times.
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if kind == 0x02:
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byte_count = 1
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elif kind == 0x03:
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byte_count = 2
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else:
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raise AssertionError()
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if debug:
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print(f"Repeat {byte_count}-byte value")
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# The byte(s) to repeat, stored as a variable-length integer. The value is treated as unsigned, i. e. the integer is never negative.
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to_repeat_int = common.read_variable_length_integer(stream)
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try:
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to_repeat = to_repeat_int.to_bytes(byte_count, "big", signed=False)
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except OverflowError:
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raise common.DecompressError(f"Value to repeat out of range for {byte_count}-byte repeat: {to_repeat_int:#x}")
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count = common.read_variable_length_integer(stream) + 1
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if count <= 0:
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raise common.DecompressError(f"Repeat count must be positive: {count}")
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if debug:
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print(f"\t-> {to_repeat} * {count}")
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yield to_repeat * count
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elif kind == 0x04:
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# A sequence of 16-bit signed integers, with each integer encoded as a difference relative to the previous integer. The first integer is stored explicitly.
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if debug:
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print(f"Difference-encoded 16-bit integers")
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# The first integer is stored explicitly, as a signed value.
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initial_int = common.read_variable_length_integer(stream)
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try:
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initial = initial_int.to_bytes(2, "big", signed=True)
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except OverflowError:
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raise common.DecompressError(f"Initial value out of range for 16-bit integer difference encoding: {initial_int:#x}")
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if debug:
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print(f"\t-> initial: 0x{initial_int:>04x}")
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yield initial
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count = common.read_variable_length_integer(stream)
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if count < 0:
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raise common.DecompressError(f"Count cannot be negative: {count}")
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# To make the following calculations simpler, the signed initial_int value is converted to unsigned.
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current_int = initial_int & 0xffff
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for _ in range(count):
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# The difference to the previous integer is stored as an 8-bit signed integer.
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# The usual variable-length integer format is *not* used here.
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diff = int.from_bytes(common.read_exact(stream, 1), "big", signed=True)
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# Simulate 16-bit integer wraparound.
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current_int = (current_int + diff) & 0xffff
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if debug:
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print(f"\t-> difference {diff:#x}: 0x{current_int:>04x}")
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yield current_int.to_bytes(2, "big", signed=False)
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elif kind == 0x06:
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# A sequence of 32-bit signed integers, with each integer encoded as a difference relative to the previous integer. The first integer is stored explicitly.
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if debug:
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print(f"Difference-encoded 32-bit integers")
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# The first integer is stored explicitly, as a signed value.
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initial_int = common.read_variable_length_integer(stream)
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try:
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initial = initial_int.to_bytes(4, "big", signed=True)
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except OverflowError:
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raise common.DecompressError(f"Initial value out of range for 32-bit integer difference encoding: {initial_int:#x}")
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if debug:
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print(f"\t-> initial: 0x{initial_int:>08x}")
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yield initial
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count = common.read_variable_length_integer(stream)
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assert count >= 0
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# To make the following calculations simpler, the signed initial_int value is converted to unsigned.
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current_int = initial_int & 0xffffffff
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for _ in range(count):
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# The difference to the previous integer is stored as a variable-length integer, whose value may be negative.
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diff = common.read_variable_length_integer(stream)
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# Simulate 32-bit integer wraparound.
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current_int = (current_int + diff) & 0xffffffff
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if debug:
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print(f"\t-> difference {diff:#x}: 0x{current_int:>08x}")
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yield current_int.to_bytes(4, "big", signed=False)
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else:
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raise common.DecompressError(f"Unknown extended code: 0x{kind:>02x}")
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elif byte == 0xff:
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# End of data marker, always occurs exactly once as the last byte of the compressed data.
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if debug:
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print("End marker")
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# Check that there really is no more data left.
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extra = stream.read(1)
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if extra:
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raise common.DecompressError(f"Extra data encountered after end of data marker (first extra byte: {extra})")
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break
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else:
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raise common.DecompressError(f"Unknown tag byte: 0x{byte:>02x}")
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def decompress_stream(header_info: common.CompressedHeaderInfo, stream: typing.BinaryIO, *, debug: bool=False) -> typing.Iterator[bytes]:
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"""Decompress compressed data in the format used by 'dcmp' (0)."""
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decompressed_length = 0
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for chunk in decompress_stream_inner(header_info, stream, debug=debug):
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if debug:
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print(f"\t-> {chunk}")
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if header_info.decompressed_length % 2 != 0 and decompressed_length + len(chunk) == header_info.decompressed_length + 1:
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# Special case: if the decompressed data length stored in the header is odd and one less than the length of the actual decompressed data, drop the last byte.
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# This is necessary because nearly all codes generate data in groups of 2 or 4 bytes, so it is basically impossible to represent data with an odd length using this compression format.
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decompressed_length += len(chunk) - 1
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yield chunk[:-1]
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else:
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decompressed_length += len(chunk)
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yield chunk
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if debug:
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print(f"Decompressed {decompressed_length:#x} bytes so far")
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