Refactor the rsrcfork.compress module into separate submodules
Each decompressor now has its own module, since they share almost no code between each other.
This commit is contained in:
dgelessus
parent
4c32987cc3
commit
8904f6e093
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@ -1,721 +0,0 @@
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import enum
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import struct
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import typing
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__all__ = [
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"DecompressError",
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"decompress",
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]
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# The signature of all compressed resource data, 0xa89f6572 in hex, or "®üer" in MacRoman.
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COMPRESSED_SIGNATURE = b"\xa8\x9fer"
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# The compression type commonly used for application resources.
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COMPRESSED_TYPE_APPLICATION = 0x0801
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# The compression type commonly used for System file resources.
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COMPRESSED_TYPE_SYSTEM = 0x0901
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# Common header for compressed resources of all types.
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# 4 bytes: Signature (see above).
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# 2 bytes: Length of the complete header (this common part and the type-specific part that follows it). (This meaning is just a guess - the field's value is always 0x0012, so there's no way to know for certain what it means.)
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# 2 bytes: Compression type. Known so far: 0x0901 is used in the System file's resources. 0x0801 is used in other files' resources.
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# 4 bytes: Length of the data after decompression.
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STRUCT_COMPRESSED_HEADER = struct.Struct(">4sHHI")
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# Header continuation part for an "application" compressed resource.
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# 1 byte: "Working buffer fractional size" - the ratio of the compressed data size to the uncompressed data size, times 256.
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# 1 byte: "Expansion buffer size" - the maximum number of bytes that the data might grow during decompression.
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# 2 bytes: The ID of the 'dcmp' resource that can decompress this resource. Currently only ID 0 is supported.
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# 2 bytes: Reserved (always zero).
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STRUCT_COMPRESSED_APPLICATION_HEADER = struct.Struct(">BBhH")
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# Lookup table for codes in range(0x4b, 0xfe) in 'dcmp' (0)-compressed resources.
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# This table was obtained by decompressing a manually created compressed resource that refers to every possible table entry. Detailed steps:
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# 1. Create a file with a resource fork
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# 2. Add a resource with the following contents: 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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# 3. Set the "compressed" flag (0x01) on the resource
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# 4. Open the file in ResEdit
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# 5. Duplicate the resource - this will decompress the original resource and write its contents uncompressed into the duplicate
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# 6. Read the data from the duplicated resource
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COMPRESSED_APPLICATION_0_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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COMPRESSED_APPLICATION_0_TABLE = [COMPRESSED_APPLICATION_0_TABLE_DATA[i:i + 2] for i in range(0, len(COMPRESSED_APPLICATION_0_TABLE_DATA), 2)]
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assert len(COMPRESSED_APPLICATION_0_TABLE) == len(range(0x4b, 0xfe))
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# Lookup table for codes in range(0xd5, 0xfe) in 'dcmp' (1)-compressed resources.
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# This table was obtained by decompressing a manually created compressed resource that refers to every possible table entry. Detailed steps:
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# 1. Create a file with a resource fork
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# 2. Add a resource with the following contents: b'\xa8\x9fer\x00\x12\x08\x01\x00\x00\x00R\x80\x03\x00\x01\x00\x00' + bytes(range(0xd5, 0xfe)) + b'\xff'
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# 3. Set the "compressed" flag (0x01) on the resource
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# 4. Open the file in ResEdit
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# 5. Duplicate the resource - this will decompress the original resource and write its contents uncompressed into the duplicate
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# 6. Read the data from the duplicated resource
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COMPRESSED_APPLICATION_1_TABLE_DATA = (
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# First line corresponds to codes in range(0xd5, 0xd8).
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b"\x00\x00\x00\x01\x00\x02"
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# All following lines correspond to 8 codes each.
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b"\x00\x03.\x01>\x01\x01\x01\x1e\x01\xff\xff\x0e\x011\x00"
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b"\x11\x12\x01\x0732\x129\xed\x10\x01'#\"\x017"
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b"\x07\x06\x01\x17\x01#\x00\xff\x00/\x07\x0e\xfd<\x015"
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b"\x01\x15\x01\x02\x00\x07\x00>\x05\xd5\x02\x01\x06\x07\x07\x08"
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# Last line corresponds to codes in range(0xf8, 0xfe).
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b"0\x01\x013\x00\x10\x17\x167>67"
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)
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# Note: index 0 in this table corresponds to code 0xd5, index 1 to 0xd6, etc.
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COMPRESSED_APPLICATION_1_TABLE = [COMPRESSED_APPLICATION_1_TABLE_DATA[i:i + 2] for i in range(0, len(COMPRESSED_APPLICATION_1_TABLE_DATA), 2)]
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assert len(COMPRESSED_APPLICATION_1_TABLE) == len(range(0xd5, 0xfe))
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# Header continuation part for a "system" compressed resource.
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# 2 bytes: The ID of the 'dcmp' resource that can decompress this resource. Currently only ID 2 is supported.
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# 2 bytes: Unknown meaning, doesn't appear to have any effect on the decompression algorithm. Usually zero, sometimes set to a small integer (< 10). On 'lpch' resources, the value is always nonzero, and sometimes larger than usual.
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# 1 byte: Number of entries in the custom lookup table minus one. Set to zero if the default lookup table is used.
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# 1 byte: Flags. See the CompressedSystemFlags enum below for details.
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STRUCT_COMPRESSED_SYSTEM_HEADER = struct.Struct(">hHBB")
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# Default lookup table for "system" compressed resources.
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# If the custom table flag is set, a custom table (usually with fewer than 256 entries) is used instead of this one.
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# This table was obtained by decompressing a manually created compressed resource that refers to every possible table entry. Detailed steps:
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# 1. Create a file with a resource fork
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# 2. Add a resource with the following contents: b'\xa8\x9fer\x00\x12\t\x01\x00\x00\x02\x00\x00\x02\x00\x00\x00\x00' + bytes(range(256))
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# 3. Set the "compressed" flag (0x01) on the resource
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# 4. Open the file in ResEdit
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# 5. Duplicate the resource - this will decompress the original resource and write its contents uncompressed into the duplicate
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# 6. Read the data from the duplicated resource
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COMPRESSED_DEFAULT_TABLE_DATA = (
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b"\x00\x00\x00\x08N\xba nNu\x00\x0c\x00\x04p\x00"
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b"\x00\x10\x00\x02Hn\xff\xfc`\x00\x00\x01H\xe7/."
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b"NV\x00\x06N^/\x00a\x00\xff\xf8/\x0b\xff\xff"
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b"\x00\x14\x00\n\x00\x18 _\x00\x0e P?<\xff\xf4"
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b"L\xee0.g\x00L\xdf&n\x00\x12\x00\x1cBg"
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b"\xff\xf00</\x0c\x00\x03N\xd0\x00 p\x01\x00\x16"
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b"-@H\xc0 xr\x00X\x8ff\x00O\xefB\xa7"
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b"g\x06\xff\xfaU\x8f(n?\x00\xff\xfe/<g\x04"
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b"Y\x8f k\x00$ \x1fA\xfa\x81\xe1f\x04g\x08"
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b"\x00\x1aN\xb9P\x8f .\x00\x07N\xb0\xff\xf2=@"
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b"\x00\x1e hf\x06\xff\xf6N\xf9\x08\x00\x0c@=|"
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b"\xff\xec\x00\x05 <\xff\xe8\xde\xfcJ.\x000\x00("
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b"/\x08 \x0b`\x02Bn-H S @\x18\x00"
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b"`\x04A\xee/(/\x01g\nH@ \x07f\x08"
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b"\x01\x18/\x070(?.0+\"n/+\x00,"
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b"g\x0c\"_`\x06\x00\xff0\x07\xff\xeeS@\x00@"
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b"\xff\xe4J@f\n\x00\x0fN\xadp\xff\"\xd8Hk"
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b"\x00\" Kg\x0eJ\xaeN\x90\xff\xe0\xff\xc0\x00*"
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b"'@g\x02Q\xc8\x02\xb6Hz\"x\xb0n\xff\xe6"
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b"\x00\t2.>\x00HA\xff\xeaC\xeeNqt\x00"
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b"/, l\x00<\x00&\x00P\x18\x800\x1f\"\x00"
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b"f\x0c\xff\xda\x008f\x020, \x0c-nB@"
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b"\xff\xe2\xa9\xf0\xff\x007|\xe5\x80\xff\xdcHhYO"
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b"\x004>\x1f`\x08/\x06\xff\xde`\np\x02\x002"
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b"\xff\xcc\x00\x80\"Q\x10\x1f1|\xa0)\xff\xd8R@"
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b"\x01\x00g\x10\xa0#\xff\xce\xff\xd4 \x06Hx\x00."
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b"POC\xfag\x12v\x00A\xe8Jn \xd9\x00Z"
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b"\x7f\xffQ\xca\x00\\.\x00\x02@H\xc7g\x14\x0c\x80"
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b".\x9f\xff\xd6\x80\x00\x10\x00HBJk\xff\xd2\x00H"
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b"JGN\xd1 o\x00A`\x0c*xB.2\x00"
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b"etg\x16\x00DHm \x08Hl\x0b|&@"
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b"\x04\x00\x00h m\x00\r*@\x00\x0b\x00>\x02 "
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)
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COMPRESSED_DEFAULT_TABLE = [COMPRESSED_DEFAULT_TABLE_DATA[i:i + 2] for i in range(0, len(COMPRESSED_DEFAULT_TABLE_DATA), 2)]
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class CompressedSystemFlags(enum.Flag):
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TAGGED = 1 << 1 # The compressed data is tagged, meaning that it consists of "blocks" of a tag byte followed by 8 table references and/or literals. See comments in the decompress function for details.
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CUSTOM_TABLE = 1 << 0 # A custom lookup table is included before the compressed data, which is used instead of the default table.
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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 _split_bits(i: int) -> typing.Tuple[bool, bool, bool, bool, bool, bool, bool, bool]:
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"""Split a byte (an int) into its 8 bits (a tuple of 8 bools)."""
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assert i in range(256)
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return (
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bool(i & (1 << 7)),
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bool(i & (1 << 6)),
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bool(i & (1 << 5)),
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bool(i & (1 << 4)),
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bool(i & (1 << 3)),
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bool(i & (1 << 2)),
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bool(i & (1 << 1)),
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bool(i & (1 << 0)),
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)
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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 "application" compressed resources.
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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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def _decompress_application_0(data: bytes, decompressed_length: int, *, debug: bool=False) -> bytes:
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prev_literals = []
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decompressed = b""
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i = 0
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while i < len(data):
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byte = data[i]
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if debug:
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print(f"Tag byte 0x{byte:>02x}, at 0x{i:x}, decompressing to 0x{len(decompressed):x}")
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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 = data[i+1]
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begin = i + 2
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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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begin = i + 1
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end = begin + 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 = data[begin:end]
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if debug:
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print(f"Literal (storing: {do_store})")
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print(f"\t-> {literal}")
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decompressed += literal
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if do_store:
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if debug:
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print(f"\t-> stored as literal number 0x{len(prev_literals):x}")
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prev_literals.append(literal)
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i = end
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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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table_index = 0x28 + ((byte - 0x20) << 8 | data[i+1])
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i += 2
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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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literal = prev_literals[table_index]
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if debug:
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print(f"\t-> {literal}")
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decompressed += literal
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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(data[i+1:i+3], "big", signed=False)
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i += 3
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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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literal = prev_literals[table_index]
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if debug:
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print(f"\t-> {literal}")
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decompressed += literal
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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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i += 1
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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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literal = prev_literals[table_index]
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if debug:
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print(f"\t-> {literal}")
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decompressed += literal
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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 resource use the same table.
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table_index = byte - 0x4b
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i += 1
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if debug:
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print(f"Fixed table reference to 0x{table_index:>02x}")
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entry = COMPRESSED_APPLICATION_0_TABLE[table_index]
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if debug:
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print(f"\t-> {entry}")
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decompressed += entry
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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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i += 1
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kind = data[i]
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if debug:
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print(f"Extended code: 0x{kind:>02x}")
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i += 1
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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, length = _read_variable_length_integer(data, i)
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i += length
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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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if debug:
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print(f"\t-> tail of first entry: {entry_tail}")
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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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decompressed += entry_tail
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count, length = _read_variable_length_integer(data, i)
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i += length
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if count <= 0:
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raise 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, length = _read_variable_length_integer(data, i)
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i += length
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if debug:
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print(f"-> address of second entry: {current_int:#x}")
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entry = current_int.to_bytes(2, "big", signed=False) + entry_tail
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if debug:
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print(f"-> second entry: {entry}")
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decompressed += entry
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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, length = _read_variable_length_integer(data, i)
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i += length
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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}")
|
||||
entry = current_int.to_bytes(2, "big", signed=False) + entry_tail
|
||||
if debug:
|
||||
print(f"\t-> {entry}")
|
||||
decompressed += entry
|
||||
elif kind in (0x02, 0x03):
|
||||
# Repeat 1 or 2 bytes a certain number of times.
|
||||
|
||||
if kind == 0x02:
|
||||
byte_count = 1
|
||||
elif kind == 0x03:
|
||||
byte_count = 2
|
||||
else:
|
||||
raise AssertionError()
|
||||
|
||||
if debug:
|
||||
print(f"Repeat {byte_count}-byte value")
|
||||
|
||||
# The byte(s) to repeat, stored as a variable-length integer. The value is treated as unsigned, i. e. the integer is never negative.
|
||||
to_repeat_int, length = _read_variable_length_integer(data, i)
|
||||
i += length
|
||||
try:
|
||||
to_repeat = to_repeat_int.to_bytes(byte_count, "big", signed=False)
|
||||
except OverflowError:
|
||||
raise DecompressError(f"Value to repeat out of range for {byte_count}-byte repeat: {to_repeat_int:#x}")
|
||||
|
||||
count_m1, length = _read_variable_length_integer(data, i)
|
||||
i += length
|
||||
count = count_m1 + 1
|
||||
if count <= 0:
|
||||
raise DecompressError(f"Repeat count must be positive: {count}")
|
||||
|
||||
repeated = to_repeat * count
|
||||
if debug:
|
||||
print(f"\t-> {to_repeat} * {count}: {repeated}")
|
||||
decompressed += repeated
|
||||
elif kind == 0x04:
|
||||
# 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.
|
||||
|
||||
if debug:
|
||||
print(f"Difference-encoded 16-bit integers")
|
||||
|
||||
# The first integer is stored explicitly, as a signed value.
|
||||
initial_int, length = _read_variable_length_integer(data, i)
|
||||
i += length
|
||||
try:
|
||||
initial = initial_int.to_bytes(2, "big", signed=True)
|
||||
except OverflowError:
|
||||
raise DecompressError(f"Initial value out of range for 16-bit integer difference encoding: {initial_int:#x}")
|
||||
if debug:
|
||||
print(f"\t-> initial: {initial}")
|
||||
decompressed += initial
|
||||
|
||||
count, length = _read_variable_length_integer(data, i)
|
||||
i += length
|
||||
if count < 0:
|
||||
raise DecompressError(f"Count cannot be negative: {count}")
|
||||
|
||||
# To make the following calculations simpler, the signed initial_int value is converted to unsigned.
|
||||
current_int = initial_int & 0xffff
|
||||
for _ in range(count):
|
||||
# The difference to the previous integer is stored as an 8-bit signed integer.
|
||||
# The usual variable-length integer format is *not* used here.
|
||||
diff = int.from_bytes(data[i:i+1], "big", signed=True)
|
||||
i += 1
|
||||
|
||||
# Simulate 16-bit integer wraparound.
|
||||
current_int = (current_int + diff) & 0xffff
|
||||
current = current_int.to_bytes(2, "big", signed=False)
|
||||
if debug:
|
||||
print(f"\t-> difference {diff:#x}: {current}")
|
||||
decompressed += current
|
||||
elif kind == 0x06:
|
||||
# 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.
|
||||
|
||||
if debug:
|
||||
print(f"Difference-encoded 16-bit integers")
|
||||
|
||||
# The first integer is stored explicitly, as a signed value.
|
||||
initial_int, length = _read_variable_length_integer(data, i)
|
||||
i += length
|
||||
try:
|
||||
initial = initial_int.to_bytes(4, "big", signed=True)
|
||||
except OverflowError:
|
||||
raise DecompressError(f"Initial value out of range for 32-bit integer difference encoding: {initial_int:#x}")
|
||||
if debug:
|
||||
print(f"\t-> initial: {initial}")
|
||||
decompressed += initial
|
||||
|
||||
count, length = _read_variable_length_integer(data, i)
|
||||
i += length
|
||||
assert count >= 0
|
||||
|
||||
# To make the following calculations simpler, the signed initial_int value is converted to unsigned.
|
||||
current_int = initial_int & 0xffffffff
|
||||
for _ in range(count):
|
||||
# The difference to the previous integer is stored as a variable-length integer, whose value may be negative.
|
||||
diff, length = _read_variable_length_integer(data, i)
|
||||
i += length
|
||||
|
||||
# Simulate 32-bit integer wraparound.
|
||||
current_int = (current_int + diff) & 0xffffffff
|
||||
current = current_int.to_bytes(4, "big", signed=False)
|
||||
if debug:
|
||||
print(f"\t-> difference {diff:#x}: {current}")
|
||||
decompressed += current
|
||||
else:
|
||||
raise DecompressError(f"Unknown extended code: 0x{kind:>02x}")
|
||||
elif byte == 0xff:
|
||||
# End of data marker, always occurs exactly once as the last byte of the compressed data.
|
||||
if debug:
|
||||
print("End marker")
|
||||
if i != len(data) - 1:
|
||||
raise DecompressError(f"End marker reached at {i}, before the expected end of data at {len(data) - 1}")
|
||||
i += 1
|
||||
else:
|
||||
raise DecompressError(f"Unknown tag byte: 0x{data[i]:>02x}")
|
||||
|
||||
if decompressed_length % 2 != 0 and len(decompressed) == decompressed_length + 1:
|
||||
# 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.
|
||||
# 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.
|
||||
decompressed = decompressed[:-1]
|
||||
|
||||
return decompressed
|
||||
|
||||
|
||||
def _decompress_application_1(data: bytes, decompressed_length: int, *, debug: bool=False) -> bytes:
|
||||
prev_literals = []
|
||||
decompressed = b""
|
||||
|
||||
i = 0
|
||||
|
||||
while i < len(data):
|
||||
byte = data[i]
|
||||
if debug:
|
||||
print(f"Tag byte 0x{byte:>02x}, at 0x{i:x}, decompressing to 0x{len(decompressed):x}")
|
||||
|
||||
if byte in range(0x00, 0x20):
|
||||
# Literal byte sequence, 1-byte header.
|
||||
# The length of the literal data is stored in the low nibble of the tag byte.
|
||||
count = (byte >> 0 & 0xf) + 1
|
||||
begin = i + 1
|
||||
end = begin + count
|
||||
# Controls whether or not the literal is stored so that it can be referenced again later.
|
||||
do_store = byte >= 0x10
|
||||
literal = data[begin:end]
|
||||
if debug:
|
||||
print(f"Literal (1-byte header, storing: {do_store})")
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
if do_store:
|
||||
if debug:
|
||||
print(f"\t-> stored as literal number 0x{len(prev_literals):x}")
|
||||
prev_literals.append(literal)
|
||||
i = end
|
||||
elif byte in range(0x20, 0xd0):
|
||||
# Backreference to a previous literal, 1-byte form.
|
||||
# This can reference literals with indices in range(0xb0).
|
||||
table_index = byte - 0x20
|
||||
i += 1
|
||||
if debug:
|
||||
print(f"Backreference (1-byte form) to 0x{table_index:>02x}")
|
||||
literal = prev_literals[table_index]
|
||||
if debug:
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
elif byte in (0xd0, 0xd1):
|
||||
# Literal byte sequence, 2-byte header.
|
||||
# The length of the literal data is stored in the following byte.
|
||||
count = data[i+1]
|
||||
begin = i + 2
|
||||
end = begin + count
|
||||
# Controls whether or not the literal is stored so that it can be referenced again later.
|
||||
do_store = byte == 0xd1
|
||||
literal = data[begin:end]
|
||||
if debug:
|
||||
print(f"Literal (2-byte header, storing: {do_store})")
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
if do_store:
|
||||
if debug:
|
||||
print(f"\t-> stored as literal number 0x{len(prev_literals):x}")
|
||||
prev_literals.append(literal)
|
||||
i = end
|
||||
elif byte == 0xd2:
|
||||
# Backreference to a previous literal, 2-byte form.
|
||||
# This can reference literals with indices in range(0xb0, 0x1b0).
|
||||
table_index = data[i+1] + 0xb0
|
||||
i += 2
|
||||
if debug:
|
||||
print(f"Backreference (2-byte form) to 0x{table_index:>02x}")
|
||||
literal = prev_literals[table_index]
|
||||
if debug:
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
elif byte in range(0xd5, 0xfe):
|
||||
# Reference into a fixed table of two-byte literals.
|
||||
# All compressed resources use the same table.
|
||||
table_index = byte - 0xd5
|
||||
i += 1
|
||||
if debug:
|
||||
print(f"Fixed table reference to 0x{table_index:>02x}")
|
||||
entry = COMPRESSED_APPLICATION_1_TABLE[table_index]
|
||||
if debug:
|
||||
print(f"\t-> {entry}")
|
||||
decompressed += entry
|
||||
elif byte == 0xfe:
|
||||
# Extended code, whose meaning is controlled by the following byte.
|
||||
|
||||
i += 1
|
||||
kind = data[i]
|
||||
if debug:
|
||||
print(f"Extended code: 0x{kind:>02x}")
|
||||
i += 1
|
||||
|
||||
if kind == 0x02:
|
||||
# Repeat 1 byte a certain number of times.
|
||||
|
||||
byte_count = 1 # Unlike with 'dcmp' (0) compression, there doesn't appear to be a 2-byte repeat (or if there is, it's never used in practice).
|
||||
|
||||
if debug:
|
||||
print(f"Repeat {byte_count}-byte value")
|
||||
|
||||
# The byte(s) to repeat, stored as a variable-length integer. The value is treated as unsigned, i. e. the integer is never negative.
|
||||
to_repeat_int, length = _read_variable_length_integer(data, i)
|
||||
i += length
|
||||
try:
|
||||
to_repeat = to_repeat_int.to_bytes(byte_count, "big", signed=False)
|
||||
except OverflowError:
|
||||
raise DecompressError(f"Value to repeat out of range for {byte_count}-byte repeat: {to_repeat_int:#x}")
|
||||
|
||||
count_m1, length = _read_variable_length_integer(data, i)
|
||||
i += length
|
||||
count = count_m1 + 1
|
||||
if count <= 0:
|
||||
raise DecompressError(f"Repeat count must be positive: {count}")
|
||||
|
||||
repeated = to_repeat * count
|
||||
if debug:
|
||||
print(f"\t-> {to_repeat} * {count}: {repeated}")
|
||||
decompressed += repeated
|
||||
else:
|
||||
raise DecompressError(f"Unknown extended code: 0x{kind:>02x}")
|
||||
elif byte == 0xff:
|
||||
# End of data marker, always occurs exactly once as the last byte of the compressed data.
|
||||
if debug:
|
||||
print("End marker")
|
||||
if i != len(data) - 1:
|
||||
raise DecompressError(f"End marker reached at {i}, before the expected end of data at {len(data) - 1}")
|
||||
i += 1
|
||||
else:
|
||||
raise DecompressError(f"Unknown tag byte: 0x{data[i]:>02x}")
|
||||
|
||||
return decompressed
|
||||
|
||||
|
||||
def _decompress_application(data: bytes, decompressed_length: int, *, debug: bool=False) -> bytes:
|
||||
working_buffer_fractional_size, expansion_buffer_size, dcmp_id, reserved = STRUCT_COMPRESSED_APPLICATION_HEADER.unpack_from(data)
|
||||
|
||||
if debug:
|
||||
print(f"Working buffer fractional size: {working_buffer_fractional_size} (=> {len(data) * 256 / working_buffer_fractional_size})")
|
||||
print(f"Expansion buffer size: {expansion_buffer_size}")
|
||||
|
||||
if dcmp_id == 0:
|
||||
decompress_func = _decompress_application_0
|
||||
elif dcmp_id == 1:
|
||||
decompress_func = _decompress_application_1
|
||||
else:
|
||||
raise DecompressError(f"Unsupported 'dcmp' ID: {dcmp_id}, expected 0 or 1")
|
||||
|
||||
if reserved != 0:
|
||||
raise DecompressError(f"Reserved field should be 0, not 0x{reserved:>04x}")
|
||||
|
||||
return decompress_func(data[STRUCT_COMPRESSED_APPLICATION_HEADER.size:], decompressed_length, debug=debug)
|
||||
|
||||
|
||||
def _decompress_system_untagged(data: bytes, decompressed_length: int, table: typing.Sequence[bytes], *, debug: bool=False) -> bytes:
|
||||
parts = []
|
||||
i = 0
|
||||
while i < len(data):
|
||||
if i == len(data) - 1 and decompressed_length % 2 != 0:
|
||||
# Special case: if we are at the last byte of the compressed data, and the decompressed data has an odd length, the last byte is a single literal byte, and not a table reference.
|
||||
if debug:
|
||||
print(f"Last byte: {data[-1:]}")
|
||||
parts.append(data[-1:])
|
||||
break
|
||||
|
||||
# Compressed data is untagged, every byte is a table reference.
|
||||
if debug:
|
||||
print(f"Reference: {data[i]} -> {table[data[i]]}")
|
||||
parts.append(table[data[i]])
|
||||
i += 1
|
||||
|
||||
return b"".join(parts)
|
||||
|
||||
def _decompress_system_tagged(data: bytes, decompressed_length: int, table: typing.Sequence[bytes], *, debug: bool=False) -> bytes:
|
||||
parts = []
|
||||
i = 0
|
||||
while i < len(data):
|
||||
if i == len(data) - 1 and decompressed_length % 2 != 0:
|
||||
# Special case: if we are at the last byte of the compressed data, and the decompressed data has an odd length, the last byte is a single literal byte, and not a tag or a table reference.
|
||||
if debug:
|
||||
print(f"Last byte: {data[-1:]}")
|
||||
parts.append(data[-1:])
|
||||
break
|
||||
|
||||
# Compressed data is tagged, each tag byte is followed by 8 table references and/or literals.
|
||||
tag = data[i]
|
||||
if debug:
|
||||
print(f"Tag: 0b{tag:>08b}")
|
||||
i += 1
|
||||
for is_ref in _split_bits(tag):
|
||||
if is_ref:
|
||||
# This is a table reference (a single byte that is an index into the table).
|
||||
if debug:
|
||||
print(f"Reference: {data[i]} -> {table[data[i]]}")
|
||||
parts.append(table[data[i]])
|
||||
i += 1
|
||||
else:
|
||||
# This is a literal (two uncompressed bytes that are literally copied into the output).
|
||||
# Note: if i == len(data)-1, the literal is actually only a single byte long.
|
||||
# This case is handled automatically - the slice extends one byte past the end of the data, and only one byte is returned.
|
||||
if debug:
|
||||
print(f"Literal: {data[i:i+2]}")
|
||||
parts.append(data[i:i + 2])
|
||||
i += 2
|
||||
|
||||
# If the end of the compressed data is reached in the middle of a chunk, all further tag bits are ignored (they should be zero) and decompression ends.
|
||||
if i >= len(data):
|
||||
break
|
||||
|
||||
return b"".join(parts)
|
||||
|
||||
def _decompress_system(data: bytes, decompressed_length: int, *, debug: bool=False) -> bytes:
|
||||
dcmp_id, unknown, table_count_m1, flags_raw = STRUCT_COMPRESSED_SYSTEM_HEADER.unpack_from(data)
|
||||
if dcmp_id != 2:
|
||||
raise DecompressError(f"Unsupported 'dcmp' ID: {dcmp_id}, expected 2")
|
||||
if debug:
|
||||
print(f"Value of unknown field at bytes 0xc-0xe: 0x{unknown:>04x}")
|
||||
|
||||
table_count = table_count_m1 + 1
|
||||
if debug:
|
||||
print(f"Table has {table_count} entries")
|
||||
|
||||
try:
|
||||
flags = CompressedSystemFlags(flags_raw)
|
||||
except ValueError:
|
||||
raise DecompressError(f"Unsupported flags set: 0b{flags_raw:>08b}, currently only bits 0 and 1 are supported")
|
||||
|
||||
if debug:
|
||||
print(f"Flags: {flags}")
|
||||
|
||||
if CompressedSystemFlags.CUSTOM_TABLE in flags:
|
||||
table_start = STRUCT_COMPRESSED_SYSTEM_HEADER.size
|
||||
data_start = table_start + table_count * 2
|
||||
table = []
|
||||
for i in range(table_start, data_start, 2):
|
||||
table.append(data[i:i + 2])
|
||||
if debug:
|
||||
print(f"Using custom table: {table}")
|
||||
else:
|
||||
if table_count_m1 != 0:
|
||||
raise DecompressError(f"table_count_m1 field is {table_count_m1}, but must be zero when the default table is used")
|
||||
table = COMPRESSED_DEFAULT_TABLE
|
||||
data_start = STRUCT_COMPRESSED_SYSTEM_HEADER.size
|
||||
if debug:
|
||||
print("Using default table")
|
||||
|
||||
if CompressedSystemFlags.TAGGED in flags:
|
||||
decompress_func = _decompress_system_tagged
|
||||
else:
|
||||
decompress_func = _decompress_system_untagged
|
||||
|
||||
return decompress_func(data[data_start:], decompressed_length, table, debug=debug)
|
||||
|
||||
|
||||
def decompress(data: bytes, *, debug: bool=False) -> bytes:
|
||||
"""Decompress the given compressed resource data."""
|
||||
|
||||
try:
|
||||
signature, header_length, compression_type, decompressed_length = STRUCT_COMPRESSED_HEADER.unpack_from(data)
|
||||
except struct.error:
|
||||
raise DecompressError(f"Invalid header")
|
||||
if signature != COMPRESSED_SIGNATURE:
|
||||
raise DecompressError(f"Invalid signature: {signature!r}, expected {COMPRESSED_SIGNATURE}")
|
||||
if header_length != 0x12:
|
||||
raise DecompressError(f"Unsupported header length: 0x{header_length:>04x}, expected 0x12")
|
||||
|
||||
if compression_type == COMPRESSED_TYPE_APPLICATION:
|
||||
decompress_func = _decompress_application
|
||||
elif compression_type == COMPRESSED_TYPE_SYSTEM:
|
||||
decompress_func = _decompress_system
|
||||
else:
|
||||
raise DecompressError(f"Unsupported compression type: 0x{compression_type:>04x}")
|
||||
|
||||
if debug:
|
||||
print(f"Decompressed length: {decompressed_length}")
|
||||
|
||||
decompressed = decompress_func(data[STRUCT_COMPRESSED_HEADER.size:], decompressed_length, debug=debug)
|
||||
if len(decompressed) != decompressed_length:
|
||||
raise DecompressError(f"Actual length of decompressed data ({len(decompressed)}) does not match length stored in resource ({decompressed_length})")
|
||||
return decompressed
|
||||
|
|
@ -0,0 +1,97 @@
|
|||
import struct
|
||||
|
||||
from . import dcmp0
|
||||
from . import dcmp1
|
||||
from . import dcmp2
|
||||
|
||||
from .common import DecompressError
|
||||
|
||||
__all__ = [
|
||||
"DecompressError",
|
||||
"decompress",
|
||||
]
|
||||
|
||||
# The signature of all compressed resource data, 0xa89f6572 in hex, or "®üer" in MacRoman.
|
||||
COMPRESSED_SIGNATURE = b"\xa8\x9fer"
|
||||
# The compression type commonly used for application resources.
|
||||
COMPRESSED_TYPE_APPLICATION = 0x0801
|
||||
# The compression type commonly used for System file resources.
|
||||
COMPRESSED_TYPE_SYSTEM = 0x0901
|
||||
|
||||
# Common header for compressed resources of all types.
|
||||
# 4 bytes: Signature (see above).
|
||||
# 2 bytes: Length of the complete header (this common part and the type-specific part that follows it). (This meaning is just a guess - the field's value is always 0x0012, so there's no way to know for certain what it means.)
|
||||
# 2 bytes: Compression type. Known so far: 0x0901 is used in the System file's resources. 0x0801 is used in other files' resources.
|
||||
# 4 bytes: Length of the data after decompression.
|
||||
STRUCT_COMPRESSED_HEADER = struct.Struct(">4sHHI")
|
||||
|
||||
# Header continuation part for an "application" compressed resource.
|
||||
# 1 byte: "Working buffer fractional size" - the ratio of the compressed data size to the uncompressed data size, times 256.
|
||||
# 1 byte: "Expansion buffer size" - the maximum number of bytes that the data might grow during decompression.
|
||||
# 2 bytes: The ID of the 'dcmp' resource that can decompress this resource. Currently only ID 0 is supported.
|
||||
# 2 bytes: Reserved (always zero).
|
||||
STRUCT_COMPRESSED_APPLICATION_HEADER = struct.Struct(">BBhH")
|
||||
|
||||
# Header continuation part for a "system" compressed resource.
|
||||
# 2 bytes: The ID of the 'dcmp' resource that can decompress this resource. Currently only ID 2 is supported.
|
||||
# 4 bytes: Decompressor-specific parameters.
|
||||
STRUCT_COMPRESSED_SYSTEM_HEADER = struct.Struct(">h4s")
|
||||
|
||||
|
||||
def _decompress_application(data: bytes, decompressed_length: int, *, debug: bool=False) -> bytes:
|
||||
working_buffer_fractional_size, expansion_buffer_size, dcmp_id, reserved = STRUCT_COMPRESSED_APPLICATION_HEADER.unpack_from(data)
|
||||
|
||||
if debug:
|
||||
print(f"Working buffer fractional size: {working_buffer_fractional_size} (=> {len(data) * 256 / working_buffer_fractional_size})")
|
||||
print(f"Expansion buffer size: {expansion_buffer_size}")
|
||||
|
||||
if dcmp_id == 0:
|
||||
decompress_func = dcmp0.decompress
|
||||
elif dcmp_id == 1:
|
||||
decompress_func = dcmp1.decompress
|
||||
else:
|
||||
raise DecompressError(f"Unsupported 'dcmp' ID: {dcmp_id}, expected 0 or 1")
|
||||
|
||||
if reserved != 0:
|
||||
raise DecompressError(f"Reserved field should be 0, not 0x{reserved:>04x}")
|
||||
|
||||
return decompress_func(data[STRUCT_COMPRESSED_APPLICATION_HEADER.size:], decompressed_length, debug=debug)
|
||||
|
||||
|
||||
def _decompress_system(data: bytes, decompressed_length: int, *, debug: bool=False) -> bytes:
|
||||
dcmp_id, params = STRUCT_COMPRESSED_SYSTEM_HEADER.unpack_from(data)
|
||||
|
||||
if dcmp_id == 2:
|
||||
decompress_func = dcmp2.decompress
|
||||
else:
|
||||
raise DecompressError(f"Unsupported 'dcmp' ID: {dcmp_id}, expected 2")
|
||||
|
||||
return decompress_func(data[STRUCT_COMPRESSED_SYSTEM_HEADER.size:], decompressed_length, params, debug=debug)
|
||||
|
||||
|
||||
def decompress(data: bytes, *, debug: bool=False) -> bytes:
|
||||
"""Decompress the given compressed resource data."""
|
||||
|
||||
try:
|
||||
signature, header_length, compression_type, decompressed_length = STRUCT_COMPRESSED_HEADER.unpack_from(data)
|
||||
except struct.error:
|
||||
raise DecompressError(f"Invalid header")
|
||||
if signature != COMPRESSED_SIGNATURE:
|
||||
raise DecompressError(f"Invalid signature: {signature!r}, expected {COMPRESSED_SIGNATURE}")
|
||||
if header_length != 0x12:
|
||||
raise DecompressError(f"Unsupported header length: 0x{header_length:>04x}, expected 0x12")
|
||||
|
||||
if compression_type == COMPRESSED_TYPE_APPLICATION:
|
||||
decompress_func = _decompress_application
|
||||
elif compression_type == COMPRESSED_TYPE_SYSTEM:
|
||||
decompress_func = _decompress_system
|
||||
else:
|
||||
raise DecompressError(f"Unsupported compression type: 0x{compression_type:>04x}")
|
||||
|
||||
if debug:
|
||||
print(f"Decompressed length: {decompressed_length}")
|
||||
|
||||
decompressed = decompress_func(data[STRUCT_COMPRESSED_HEADER.size:], decompressed_length, debug=debug)
|
||||
if len(decompressed) != decompressed_length:
|
||||
raise DecompressError(f"Actual length of decompressed data ({len(decompressed)}) does not match length stored in resource ({decompressed_length})")
|
||||
return decompressed
|
||||
|
|
@ -0,0 +1,23 @@
|
|||
import typing
|
||||
|
||||
|
||||
class DecompressError(Exception):
|
||||
"""Raised when resource data decompression fails, because the data is invalid or the compression type is not supported."""
|
||||
|
||||
|
||||
def _read_variable_length_integer(data: bytes, position: int) -> typing.Tuple[int, int]:
|
||||
"""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.
|
||||
|
||||
This variable-length integer format is used by the 0xfe codes in the compression formats used by 'dcmp' (0) and 'dcmp' (1).
|
||||
"""
|
||||
|
||||
assert len(data) > position
|
||||
if data[position] == 0xff:
|
||||
assert len(data) > position + 4
|
||||
return int.from_bytes(data[position+1:position+5], "big", signed=True), 5
|
||||
elif data[position] >= 0x80:
|
||||
assert len(data) > position + 1
|
||||
data_modified = bytes([(data[position] - 0xc0) & 0xff, data[position+1]])
|
||||
return int.from_bytes(data_modified, "big", signed=True), 2
|
||||
else:
|
||||
return int.from_bytes(data[position:position+1], "big", signed=True), 1
|
||||
|
|
@ -0,0 +1,295 @@
|
|||
from . import common
|
||||
|
||||
# Lookup table for codes in range(0x4b, 0xfe).
|
||||
# This table was obtained by decompressing a manually created compressed resource with the following contents:
|
||||
# b'\xa8\x9fer\x00\x12\x08\x01\x00\x00\x01f\x80\x03\x00\x00\x00\x00' + bytes(range(0x4b, 0xfe)) + b'\xff'
|
||||
TABLE_DATA = (
|
||||
# First line corresponds to codes in range(0x4b, 0x50).
|
||||
b"\x00\x00N\xba\x00\x08Nu\x00\x0c"
|
||||
# All following lines correspond to 8 codes each.
|
||||
b"N\xad S/\x0ba\x00\x00\x10p\x00/\x00Hn"
|
||||
b" P n/.\xff\xfcH\xe7?<\x00\x04\xff\xf8"
|
||||
b"/\x0c \x06N\xedNV hN^\x00\x01X\x8f"
|
||||
b"O\xef\x00\x02\x00\x18`\x00\xff\xffP\x8fN\x90\x00\x06"
|
||||
b"&n\x00\x14\xff\xf4L\xee\x00\n\x00\x0eA\xeeL\xdf"
|
||||
b"H\xc0\xff\xf0-@\x00\x120.p\x01/( T"
|
||||
b"g\x00\x00 \x00\x1c _\x18\x00&oHx\x00\x16"
|
||||
b"A\xfa0<(@r\x00(n \x0cf\x00 k"
|
||||
b"/\x07U\x8f\x00(\xff\xfe\xff\xec\"\xd8 \x0b\x00\x0f"
|
||||
b"Y\x8f/<\xff\x00\x01\x18\x81\xe1J\x00N\xb0\xff\xe8"
|
||||
b"H\xc7\x00\x03\x00\"\x00\x07\x00\x1ag\x06g\x08N\xf9"
|
||||
b"\x00$ x\x08\x00f\x04\x00*N\xd00(&_"
|
||||
b"g\x04\x000C\xee?\x00 \x1f\x00\x1e\xff\xf6 ."
|
||||
b"B\xa7 \x07\xff\xfa`\x02=@\x0c@f\x06\x00&"
|
||||
b"-H/\x01p\xff`\x04\x18\x80J@\x00@\x00,"
|
||||
b"/\x08\x00\x11\xff\xe4!@&@\xff\xf2BnN\xb9"
|
||||
b"=|\x008\x00\r`\x06B. <g\x0c-h"
|
||||
b"f\x08J.J\xae\x00.H@\"_\"\x00g\n"
|
||||
b"0\x07Bg\x002 (\x00\tHz\x02\x00/+"
|
||||
b"\x00\x05\"nf\x02\xe5\x80g\x0ef\n\x00P>\x00"
|
||||
b"f\x0c.\x00\xff\xee m @\xff\xe0S@`\x08"
|
||||
# Last line corresponds to codes in range(0xf8, 0xfe).
|
||||
b"\x04\x80\x00h\x0b|D\x00A\xe8HA"
|
||||
)
|
||||
# Note: index 0 in this table corresponds to code 0x4b, index 1 to 0x4c, etc.
|
||||
TABLE = [TABLE_DATA[i:i + 2] for i in range(0, len(TABLE_DATA), 2)]
|
||||
assert len(TABLE) == len(range(0x4b, 0xfe))
|
||||
|
||||
|
||||
def decompress(data: bytes, decompressed_length: int, *, debug: bool=False) -> bytes:
|
||||
"""Decompress compressed data in the format used by 'dcmp' (0)."""
|
||||
|
||||
prev_literals = []
|
||||
decompressed = b""
|
||||
|
||||
i = 0
|
||||
|
||||
while i < len(data):
|
||||
byte = data[i]
|
||||
if debug:
|
||||
print(f"Tag byte 0x{byte:>02x}, at 0x{i:x}, decompressing to 0x{len(decompressed):x}")
|
||||
|
||||
if byte in range(0x00, 0x20):
|
||||
# Literal byte sequence.
|
||||
if byte in (0x00, 0x10):
|
||||
# The length of the literal data is stored in the next byte.
|
||||
count_div2 = data[i+1]
|
||||
begin = i + 2
|
||||
else:
|
||||
# The length of the literal data is stored in the low nibble of the tag byte.
|
||||
count_div2 = byte >> 0 & 0xf
|
||||
begin = i + 1
|
||||
end = begin + 2*count_div2
|
||||
# Controls whether or not the literal is stored so that it can be referenced again later.
|
||||
do_store = byte >= 0x10
|
||||
literal = data[begin:end]
|
||||
if debug:
|
||||
print(f"Literal (storing: {do_store})")
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
if do_store:
|
||||
if debug:
|
||||
print(f"\t-> stored as literal number 0x{len(prev_literals):x}")
|
||||
prev_literals.append(literal)
|
||||
i = end
|
||||
elif byte in (0x20, 0x21):
|
||||
# Backreference to a previous literal, 2-byte form.
|
||||
# This can reference literals with index in range(0x28, 0x228).
|
||||
table_index = 0x28 + ((byte - 0x20) << 8 | data[i+1])
|
||||
i += 2
|
||||
if debug:
|
||||
print(f"Backreference (2-byte form) to 0x{table_index:>02x}")
|
||||
literal = prev_literals[table_index]
|
||||
if debug:
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
elif byte == 0x22:
|
||||
# Backreference to a previous literal, 3-byte form.
|
||||
# This can reference any literal with index 0x28 and higher, but is only necessary for literals with index 0x228 and higher.
|
||||
table_index = 0x28 + int.from_bytes(data[i+1:i+3], "big", signed=False)
|
||||
i += 3
|
||||
if debug:
|
||||
print(f"Backreference (3-byte form) to 0x{table_index:>02x}")
|
||||
literal = prev_literals[table_index]
|
||||
if debug:
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
elif byte in range(0x23, 0x4b):
|
||||
# Backreference to a previous literal, 1-byte form.
|
||||
# This can reference literals with indices in range(0x28).
|
||||
table_index = byte - 0x23
|
||||
i += 1
|
||||
if debug:
|
||||
print(f"Backreference (1-byte form) to 0x{table_index:>02x}")
|
||||
literal = prev_literals[table_index]
|
||||
if debug:
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
elif byte in range(0x4b, 0xfe):
|
||||
# Reference into a fixed table of two-byte literals.
|
||||
# All compressed resource use the same table.
|
||||
table_index = byte - 0x4b
|
||||
i += 1
|
||||
if debug:
|
||||
print(f"Fixed table reference to 0x{table_index:>02x}")
|
||||
entry = TABLE[table_index]
|
||||
if debug:
|
||||
print(f"\t-> {entry}")
|
||||
decompressed += entry
|
||||
elif byte == 0xfe:
|
||||
# Extended code, whose meaning is controlled by the following byte.
|
||||
|
||||
i += 1
|
||||
kind = data[i]
|
||||
if debug:
|
||||
print(f"Extended code: 0x{kind:>02x}")
|
||||
i += 1
|
||||
|
||||
if kind == 0x00:
|
||||
# Compact representation of (part of) a segment loader jump table, as used in 'CODE' (0) resources.
|
||||
|
||||
if debug:
|
||||
print(f"Segment loader jump table entries")
|
||||
|
||||
# All generated jump table entries have the same segment number.
|
||||
segment_number_int, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
if debug:
|
||||
print(f"\t-> segment number: {segment_number_int:#x}")
|
||||
|
||||
# The tail part of all jump table entries (i. e. everything except for the address).
|
||||
entry_tail = b"?<" + segment_number_int.to_bytes(2, "big", signed=True) + b"\xa9\xf0"
|
||||
if debug:
|
||||
print(f"\t-> tail of first entry: {entry_tail}")
|
||||
# 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.
|
||||
decompressed += entry_tail
|
||||
|
||||
count, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
if count <= 0:
|
||||
raise common.DecompressError(f"Jump table entry count must be greater than 0, not {count}")
|
||||
|
||||
# The second entry's address is stored explicitly.
|
||||
current_int, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
if debug:
|
||||
print(f"-> address of second entry: {current_int:#x}")
|
||||
entry = current_int.to_bytes(2, "big", signed=False) + entry_tail
|
||||
if debug:
|
||||
print(f"-> second entry: {entry}")
|
||||
decompressed += entry
|
||||
|
||||
for _ in range(1, count):
|
||||
# All further entries' addresses are stored as differences relative to the previous entry's address.
|
||||
diff, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
# For some reason, each difference is 6 higher than it should be.
|
||||
diff -= 6
|
||||
|
||||
# Simulate 16-bit integer wraparound.
|
||||
current_int = (current_int + diff) & 0xffff
|
||||
if debug:
|
||||
print(f"\t-> difference {diff:#x}: {current_int:#x}")
|
||||
entry = current_int.to_bytes(2, "big", signed=False) + entry_tail
|
||||
if debug:
|
||||
print(f"\t-> {entry}")
|
||||
decompressed += entry
|
||||
elif kind in (0x02, 0x03):
|
||||
# Repeat 1 or 2 bytes a certain number of times.
|
||||
|
||||
if kind == 0x02:
|
||||
byte_count = 1
|
||||
elif kind == 0x03:
|
||||
byte_count = 2
|
||||
else:
|
||||
raise AssertionError()
|
||||
|
||||
if debug:
|
||||
print(f"Repeat {byte_count}-byte value")
|
||||
|
||||
# The byte(s) to repeat, stored as a variable-length integer. The value is treated as unsigned, i. e. the integer is never negative.
|
||||
to_repeat_int, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
try:
|
||||
to_repeat = to_repeat_int.to_bytes(byte_count, "big", signed=False)
|
||||
except OverflowError:
|
||||
raise common.DecompressError(f"Value to repeat out of range for {byte_count}-byte repeat: {to_repeat_int:#x}")
|
||||
|
||||
count_m1, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
count = count_m1 + 1
|
||||
if count <= 0:
|
||||
raise common.DecompressError(f"Repeat count must be positive: {count}")
|
||||
|
||||
repeated = to_repeat * count
|
||||
if debug:
|
||||
print(f"\t-> {to_repeat} * {count}: {repeated}")
|
||||
decompressed += repeated
|
||||
elif kind == 0x04:
|
||||
# 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.
|
||||
|
||||
if debug:
|
||||
print(f"Difference-encoded 16-bit integers")
|
||||
|
||||
# The first integer is stored explicitly, as a signed value.
|
||||
initial_int, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
try:
|
||||
initial = initial_int.to_bytes(2, "big", signed=True)
|
||||
except OverflowError:
|
||||
raise common.DecompressError(f"Initial value out of range for 16-bit integer difference encoding: {initial_int:#x}")
|
||||
if debug:
|
||||
print(f"\t-> initial: {initial}")
|
||||
decompressed += initial
|
||||
|
||||
count, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
if count < 0:
|
||||
raise common.DecompressError(f"Count cannot be negative: {count}")
|
||||
|
||||
# To make the following calculations simpler, the signed initial_int value is converted to unsigned.
|
||||
current_int = initial_int & 0xffff
|
||||
for _ in range(count):
|
||||
# The difference to the previous integer is stored as an 8-bit signed integer.
|
||||
# The usual variable-length integer format is *not* used here.
|
||||
diff = int.from_bytes(data[i:i+1], "big", signed=True)
|
||||
i += 1
|
||||
|
||||
# Simulate 16-bit integer wraparound.
|
||||
current_int = (current_int + diff) & 0xffff
|
||||
current = current_int.to_bytes(2, "big", signed=False)
|
||||
if debug:
|
||||
print(f"\t-> difference {diff:#x}: {current}")
|
||||
decompressed += current
|
||||
elif kind == 0x06:
|
||||
# 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.
|
||||
|
||||
if debug:
|
||||
print(f"Difference-encoded 16-bit integers")
|
||||
|
||||
# The first integer is stored explicitly, as a signed value.
|
||||
initial_int, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
try:
|
||||
initial = initial_int.to_bytes(4, "big", signed=True)
|
||||
except OverflowError:
|
||||
raise common.DecompressError(f"Initial value out of range for 32-bit integer difference encoding: {initial_int:#x}")
|
||||
if debug:
|
||||
print(f"\t-> initial: {initial}")
|
||||
decompressed += initial
|
||||
|
||||
count, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
assert count >= 0
|
||||
|
||||
# To make the following calculations simpler, the signed initial_int value is converted to unsigned.
|
||||
current_int = initial_int & 0xffffffff
|
||||
for _ in range(count):
|
||||
# The difference to the previous integer is stored as a variable-length integer, whose value may be negative.
|
||||
diff, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
|
||||
# Simulate 32-bit integer wraparound.
|
||||
current_int = (current_int + diff) & 0xffffffff
|
||||
current = current_int.to_bytes(4, "big", signed=False)
|
||||
if debug:
|
||||
print(f"\t-> difference {diff:#x}: {current}")
|
||||
decompressed += current
|
||||
else:
|
||||
raise common.DecompressError(f"Unknown extended code: 0x{kind:>02x}")
|
||||
elif byte == 0xff:
|
||||
# End of data marker, always occurs exactly once as the last byte of the compressed data.
|
||||
if debug:
|
||||
print("End marker")
|
||||
if i != len(data) - 1:
|
||||
raise common.DecompressError(f"End marker reached at {i}, before the expected end of data at {len(data) - 1}")
|
||||
i += 1
|
||||
else:
|
||||
raise common.DecompressError(f"Unknown tag byte: 0x{data[i]:>02x}")
|
||||
|
||||
if decompressed_length % 2 != 0 and len(decompressed) == decompressed_length + 1:
|
||||
# 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.
|
||||
# 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.
|
||||
decompressed = decompressed[:-1]
|
||||
|
||||
return decompressed
|
||||
|
|
@ -0,0 +1,151 @@
|
|||
from . import common
|
||||
|
||||
# Lookup table for codes in range(0xd5, 0xfe).
|
||||
# This table was obtained by decompressing a manually created compressed resource with the following contents:
|
||||
# b'\xa8\x9fer\x00\x12\x08\x01\x00\x00\x00R\x80\x03\x00\x01\x00\x00' + bytes(range(0xd5, 0xfe)) + b'\xff'
|
||||
TABLE_DATA = (
|
||||
# First line corresponds to codes in range(0xd5, 0xd8).
|
||||
b"\x00\x00\x00\x01\x00\x02"
|
||||
# All following lines correspond to 8 codes each.
|
||||
b"\x00\x03.\x01>\x01\x01\x01\x1e\x01\xff\xff\x0e\x011\x00"
|
||||
b"\x11\x12\x01\x0732\x129\xed\x10\x01'#\"\x017"
|
||||
b"\x07\x06\x01\x17\x01#\x00\xff\x00/\x07\x0e\xfd<\x015"
|
||||
b"\x01\x15\x01\x02\x00\x07\x00>\x05\xd5\x02\x01\x06\x07\x07\x08"
|
||||
# Last line corresponds to codes in range(0xf8, 0xfe).
|
||||
b"0\x01\x013\x00\x10\x17\x167>67"
|
||||
)
|
||||
# Note: index 0 in this table corresponds to code 0xd5, index 1 to 0xd6, etc.
|
||||
TABLE = [TABLE_DATA[i:i + 2] for i in range(0, len(TABLE_DATA), 2)]
|
||||
assert len(TABLE) == len(range(0xd5, 0xfe))
|
||||
|
||||
|
||||
def decompress(data: bytes, decompressed_length: int, *, debug: bool=False) -> bytes:
|
||||
"""Decompress compressed data in the format used by 'dcmp' (1)."""
|
||||
|
||||
prev_literals = []
|
||||
decompressed = b""
|
||||
|
||||
i = 0
|
||||
|
||||
while i < len(data):
|
||||
byte = data[i]
|
||||
if debug:
|
||||
print(f"Tag byte 0x{byte:>02x}, at 0x{i:x}, decompressing to 0x{len(decompressed):x}")
|
||||
|
||||
if byte in range(0x00, 0x20):
|
||||
# Literal byte sequence, 1-byte header.
|
||||
# The length of the literal data is stored in the low nibble of the tag byte.
|
||||
count = (byte >> 0 & 0xf) + 1
|
||||
begin = i + 1
|
||||
end = begin + count
|
||||
# Controls whether or not the literal is stored so that it can be referenced again later.
|
||||
do_store = byte >= 0x10
|
||||
literal = data[begin:end]
|
||||
if debug:
|
||||
print(f"Literal (1-byte header, storing: {do_store})")
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
if do_store:
|
||||
if debug:
|
||||
print(f"\t-> stored as literal number 0x{len(prev_literals):x}")
|
||||
prev_literals.append(literal)
|
||||
i = end
|
||||
elif byte in range(0x20, 0xd0):
|
||||
# Backreference to a previous literal, 1-byte form.
|
||||
# This can reference literals with indices in range(0xb0).
|
||||
table_index = byte - 0x20
|
||||
i += 1
|
||||
if debug:
|
||||
print(f"Backreference (1-byte form) to 0x{table_index:>02x}")
|
||||
literal = prev_literals[table_index]
|
||||
if debug:
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
elif byte in (0xd0, 0xd1):
|
||||
# Literal byte sequence, 2-byte header.
|
||||
# The length of the literal data is stored in the following byte.
|
||||
count = data[i+1]
|
||||
begin = i + 2
|
||||
end = begin + count
|
||||
# Controls whether or not the literal is stored so that it can be referenced again later.
|
||||
do_store = byte == 0xd1
|
||||
literal = data[begin:end]
|
||||
if debug:
|
||||
print(f"Literal (2-byte header, storing: {do_store})")
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
if do_store:
|
||||
if debug:
|
||||
print(f"\t-> stored as literal number 0x{len(prev_literals):x}")
|
||||
prev_literals.append(literal)
|
||||
i = end
|
||||
elif byte == 0xd2:
|
||||
# Backreference to a previous literal, 2-byte form.
|
||||
# This can reference literals with indices in range(0xb0, 0x1b0).
|
||||
table_index = data[i+1] + 0xb0
|
||||
i += 2
|
||||
if debug:
|
||||
print(f"Backreference (2-byte form) to 0x{table_index:>02x}")
|
||||
literal = prev_literals[table_index]
|
||||
if debug:
|
||||
print(f"\t-> {literal}")
|
||||
decompressed += literal
|
||||
elif byte in range(0xd5, 0xfe):
|
||||
# Reference into a fixed table of two-byte literals.
|
||||
# All compressed resources use the same table.
|
||||
table_index = byte - 0xd5
|
||||
i += 1
|
||||
if debug:
|
||||
print(f"Fixed table reference to 0x{table_index:>02x}")
|
||||
entry = TABLE[table_index]
|
||||
if debug:
|
||||
print(f"\t-> {entry}")
|
||||
decompressed += entry
|
||||
elif byte == 0xfe:
|
||||
# Extended code, whose meaning is controlled by the following byte.
|
||||
|
||||
i += 1
|
||||
kind = data[i]
|
||||
if debug:
|
||||
print(f"Extended code: 0x{kind:>02x}")
|
||||
i += 1
|
||||
|
||||
if kind == 0x02:
|
||||
# Repeat 1 byte a certain number of times.
|
||||
|
||||
byte_count = 1 # Unlike with 'dcmp' (0) compression, there doesn't appear to be a 2-byte repeat (or if there is, it's never used in practice).
|
||||
|
||||
if debug:
|
||||
print(f"Repeat {byte_count}-byte value")
|
||||
|
||||
# The byte(s) to repeat, stored as a variable-length integer. The value is treated as unsigned, i. e. the integer is never negative.
|
||||
to_repeat_int, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
try:
|
||||
to_repeat = to_repeat_int.to_bytes(byte_count, "big", signed=False)
|
||||
except OverflowError:
|
||||
raise common.DecompressError(f"Value to repeat out of range for {byte_count}-byte repeat: {to_repeat_int:#x}")
|
||||
|
||||
count_m1, length = common._read_variable_length_integer(data, i)
|
||||
i += length
|
||||
count = count_m1 + 1
|
||||
if count <= 0:
|
||||
raise common.DecompressError(f"Repeat count must be positive: {count}")
|
||||
|
||||
repeated = to_repeat * count
|
||||
if debug:
|
||||
print(f"\t-> {to_repeat} * {count}: {repeated}")
|
||||
decompressed += repeated
|
||||
else:
|
||||
raise common.DecompressError(f"Unknown extended code: 0x{kind:>02x}")
|
||||
elif byte == 0xff:
|
||||
# End of data marker, always occurs exactly once as the last byte of the compressed data.
|
||||
if debug:
|
||||
print("End marker")
|
||||
if i != len(data) - 1:
|
||||
raise common.DecompressError(f"End marker reached at {i}, before the expected end of data at {len(data) - 1}")
|
||||
i += 1
|
||||
else:
|
||||
raise common.DecompressError(f"Unknown tag byte: 0x{data[i]:>02x}")
|
||||
|
||||
return decompressed
|
||||
|
|
@ -0,0 +1,175 @@
|
|||
import enum
|
||||
import struct
|
||||
import typing
|
||||
|
||||
from . import common
|
||||
|
||||
|
||||
# Parameters for a 'dcmp' (2)-compressed resource.
|
||||
# 2 bytes: Unknown meaning, doesn't appear to have any effect on the decompression algorithm. Usually zero, sometimes set to a small integer (< 10). On 'lpch' resources, the value is always nonzero, and sometimes larger than usual.
|
||||
# 1 byte: Number of entries in the custom lookup table minus one. Set to zero if the default lookup table is used.
|
||||
# 1 byte: Flags. See the ParameterFlags enum below for details.
|
||||
STRUCT_PARAMETERS = struct.Struct(">HBB")
|
||||
|
||||
# Default lookup table.
|
||||
# If the custom table flag is set, a custom table (usually with fewer than 256 entries) is used instead of this one.
|
||||
# This table was obtained by decompressing a manually created compressed resource with the following contents:
|
||||
# b'\xa8\x9fer\x00\x12\t\x01\x00\x00\x02\x00\x00\x02\x00\x00\x00\x00' + bytes(range(256))
|
||||
DEFAULT_TABLE_DATA = (
|
||||
b"\x00\x00\x00\x08N\xba nNu\x00\x0c\x00\x04p\x00"
|
||||
b"\x00\x10\x00\x02Hn\xff\xfc`\x00\x00\x01H\xe7/."
|
||||
b"NV\x00\x06N^/\x00a\x00\xff\xf8/\x0b\xff\xff"
|
||||
b"\x00\x14\x00\n\x00\x18 _\x00\x0e P?<\xff\xf4"
|
||||
b"L\xee0.g\x00L\xdf&n\x00\x12\x00\x1cBg"
|
||||
b"\xff\xf00</\x0c\x00\x03N\xd0\x00 p\x01\x00\x16"
|
||||
b"-@H\xc0 xr\x00X\x8ff\x00O\xefB\xa7"
|
||||
b"g\x06\xff\xfaU\x8f(n?\x00\xff\xfe/<g\x04"
|
||||
b"Y\x8f k\x00$ \x1fA\xfa\x81\xe1f\x04g\x08"
|
||||
b"\x00\x1aN\xb9P\x8f .\x00\x07N\xb0\xff\xf2=@"
|
||||
b"\x00\x1e hf\x06\xff\xf6N\xf9\x08\x00\x0c@=|"
|
||||
b"\xff\xec\x00\x05 <\xff\xe8\xde\xfcJ.\x000\x00("
|
||||
b"/\x08 \x0b`\x02Bn-H S @\x18\x00"
|
||||
b"`\x04A\xee/(/\x01g\nH@ \x07f\x08"
|
||||
b"\x01\x18/\x070(?.0+\"n/+\x00,"
|
||||
b"g\x0c\"_`\x06\x00\xff0\x07\xff\xeeS@\x00@"
|
||||
b"\xff\xe4J@f\n\x00\x0fN\xadp\xff\"\xd8Hk"
|
||||
b"\x00\" Kg\x0eJ\xaeN\x90\xff\xe0\xff\xc0\x00*"
|
||||
b"'@g\x02Q\xc8\x02\xb6Hz\"x\xb0n\xff\xe6"
|
||||
b"\x00\t2.>\x00HA\xff\xeaC\xeeNqt\x00"
|
||||
b"/, l\x00<\x00&\x00P\x18\x800\x1f\"\x00"
|
||||
b"f\x0c\xff\xda\x008f\x020, \x0c-nB@"
|
||||
b"\xff\xe2\xa9\xf0\xff\x007|\xe5\x80\xff\xdcHhYO"
|
||||
b"\x004>\x1f`\x08/\x06\xff\xde`\np\x02\x002"
|
||||
b"\xff\xcc\x00\x80\"Q\x10\x1f1|\xa0)\xff\xd8R@"
|
||||
b"\x01\x00g\x10\xa0#\xff\xce\xff\xd4 \x06Hx\x00."
|
||||
b"POC\xfag\x12v\x00A\xe8Jn \xd9\x00Z"
|
||||
b"\x7f\xffQ\xca\x00\\.\x00\x02@H\xc7g\x14\x0c\x80"
|
||||
b".\x9f\xff\xd6\x80\x00\x10\x00HBJk\xff\xd2\x00H"
|
||||
b"JGN\xd1 o\x00A`\x0c*xB.2\x00"
|
||||
b"etg\x16\x00DHm \x08Hl\x0b|&@"
|
||||
b"\x04\x00\x00h m\x00\r*@\x00\x0b\x00>\x02 "
|
||||
)
|
||||
DEFAULT_TABLE = [DEFAULT_TABLE_DATA[i:i + 2] for i in range(0, len(DEFAULT_TABLE_DATA), 2)]
|
||||
|
||||
|
||||
class ParameterFlags(enum.Flag):
|
||||
TAGGED = 1 << 1 # The compressed data is tagged, meaning that it consists of "blocks" of a tag byte followed by 8 table references and/or literals. See comments in the decompress function for details.
|
||||
CUSTOM_TABLE = 1 << 0 # A custom lookup table is included before the compressed data, which is used instead of the default table.
|
||||
|
||||
|
||||
def _split_bits(i: int) -> typing.Tuple[bool, bool, bool, bool, bool, bool, bool, bool]:
|
||||
"""Split a byte (an int) into its 8 bits (a tuple of 8 bools)."""
|
||||
|
||||
assert i in range(256)
|
||||
return (
|
||||
bool(i & (1 << 7)),
|
||||
bool(i & (1 << 6)),
|
||||
bool(i & (1 << 5)),
|
||||
bool(i & (1 << 4)),
|
||||
bool(i & (1 << 3)),
|
||||
bool(i & (1 << 2)),
|
||||
bool(i & (1 << 1)),
|
||||
bool(i & (1 << 0)),
|
||||
)
|
||||
|
||||
|
||||
def _decompress_system_untagged(data: bytes, decompressed_length: int, table: typing.Sequence[bytes], *, debug: bool=False) -> bytes:
|
||||
parts = []
|
||||
i = 0
|
||||
while i < len(data):
|
||||
if i == len(data) - 1 and decompressed_length % 2 != 0:
|
||||
# Special case: if we are at the last byte of the compressed data, and the decompressed data has an odd length, the last byte is a single literal byte, and not a table reference.
|
||||
if debug:
|
||||
print(f"Last byte: {data[-1:]}")
|
||||
parts.append(data[-1:])
|
||||
break
|
||||
|
||||
# Compressed data is untagged, every byte is a table reference.
|
||||
if debug:
|
||||
print(f"Reference: {data[i]} -> {table[data[i]]}")
|
||||
parts.append(table[data[i]])
|
||||
i += 1
|
||||
|
||||
return b"".join(parts)
|
||||
|
||||
def _decompress_system_tagged(data: bytes, decompressed_length: int, table: typing.Sequence[bytes], *, debug: bool=False) -> bytes:
|
||||
parts = []
|
||||
i = 0
|
||||
while i < len(data):
|
||||
if i == len(data) - 1 and decompressed_length % 2 != 0:
|
||||
# Special case: if we are at the last byte of the compressed data, and the decompressed data has an odd length, the last byte is a single literal byte, and not a tag or a table reference.
|
||||
if debug:
|
||||
print(f"Last byte: {data[-1:]}")
|
||||
parts.append(data[-1:])
|
||||
break
|
||||
|
||||
# Compressed data is tagged, each tag byte is followed by 8 table references and/or literals.
|
||||
tag = data[i]
|
||||
if debug:
|
||||
print(f"Tag: 0b{tag:>08b}")
|
||||
i += 1
|
||||
for is_ref in _split_bits(tag):
|
||||
if is_ref:
|
||||
# This is a table reference (a single byte that is an index into the table).
|
||||
if debug:
|
||||
print(f"Reference: {data[i]} -> {table[data[i]]}")
|
||||
parts.append(table[data[i]])
|
||||
i += 1
|
||||
else:
|
||||
# This is a literal (two uncompressed bytes that are literally copied into the output).
|
||||
# Note: if i == len(data)-1, the literal is actually only a single byte long.
|
||||
# This case is handled automatically - the slice extends one byte past the end of the data, and only one byte is returned.
|
||||
if debug:
|
||||
print(f"Literal: {data[i:i+2]}")
|
||||
parts.append(data[i:i + 2])
|
||||
i += 2
|
||||
|
||||
# If the end of the compressed data is reached in the middle of a chunk, all further tag bits are ignored (they should be zero) and decompression ends.
|
||||
if i >= len(data):
|
||||
break
|
||||
|
||||
return b"".join(parts)
|
||||
|
||||
|
||||
def decompress(data: bytes, decompressed_length: int, parameters: bytes, *, debug: bool=False) -> bytes:
|
||||
"""Decompress compressed data in the format used by 'dcmp' (2)."""
|
||||
|
||||
unknown, table_count_m1, flags_raw = STRUCT_PARAMETERS.unpack(parameters)
|
||||
|
||||
if debug:
|
||||
print(f"Value of unknown parameter field: 0x{unknown:>04x}")
|
||||
|
||||
table_count = table_count_m1 + 1
|
||||
if debug:
|
||||
print(f"Table has {table_count} entries")
|
||||
|
||||
try:
|
||||
flags = ParameterFlags(flags_raw)
|
||||
except ValueError:
|
||||
raise common.DecompressError(f"Unsupported flags set: 0b{flags_raw:>08b}, currently only bits 0 and 1 are supported")
|
||||
|
||||
if debug:
|
||||
print(f"Flags: {flags}")
|
||||
|
||||
if ParameterFlags.CUSTOM_TABLE in flags:
|
||||
table_start = 0
|
||||
data_start = table_start + table_count * 2
|
||||
table = []
|
||||
for i in range(table_start, data_start, 2):
|
||||
table.append(data[i:i + 2])
|
||||
if debug:
|
||||
print(f"Using custom table: {table}")
|
||||
else:
|
||||
if table_count_m1 != 0:
|
||||
raise common.DecompressError(f"table_count_m1 field is {table_count_m1}, but must be zero when the default table is used")
|
||||
table = DEFAULT_TABLE
|
||||
data_start = 0
|
||||
if debug:
|
||||
print("Using default table")
|
||||
|
||||
if ParameterFlags.TAGGED in flags:
|
||||
decompress_func = _decompress_system_tagged
|
||||
else:
|
||||
decompress_func = _decompress_system_untagged
|
||||
|
||||
return decompress_func(data[data_start:], decompressed_length, table, debug=debug)
|
||||
Loading…
Reference in New Issue