Macintosh-Tools/python-rsrcfork
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Simplify decompressor lookup

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All decompressors now have exactly the same signature (as a result,
each decompressor now has to check itself that the header type is
correct). This allows the decompressors to be stored in a simple
dictionary, which makes the lookup process much simpler.
This commit is contained in:
dgelessus 2019-09-23 23:32:38 +02:00
parent 53e73be980
commit a23cd0fcb2
4 changed files with 24 additions and 28 deletions
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37
rsrcfork/compress/__init__.py
View File

@ -10,24 +10,13 @@ __all__ = [
]
def _decompress_application(data: bytes, header_info: CompressedApplicationHeaderInfo, *, debug: bool=False) -> bytes:
if header_info.dcmp_id == 0:
decompress_func = dcmp0.decompress
elif header_info.dcmp_id == 1:
decompress_func = dcmp1.decompress
else:
raise DecompressError(f"Unsupported 'dcmp' ID: {header_info.dcmp_id}, expected 0 or 1")
return decompress_func(header_info, data, debug=debug)
def _decompress_system(data: bytes, header_info: CompressedSystemHeaderInfo, *, debug: bool=False) -> bytes:
if header_info.dcmp_id == 2:
decompress_func = dcmp2.decompress
else:
raise DecompressError(f"Unsupported 'dcmp' ID: {header_info.dcmp_id}, expected 2")
return decompress_func(header_info, data, debug=debug)
# Maps 'dcmp' IDs to their corresponding Python implementations.
# Each decompressor has the signature (header_info: CompressedHeaderInfo, data: bytes, *, debug: bool=False) -> bytes.
DECOMPRESSORS = {
0: dcmp0.decompress,
1: dcmp1.decompress,
2: dcmp2.decompress,
}
def decompress(data: bytes, *, debug: bool=False) -> bytes:
@ -38,14 +27,12 @@ def decompress(data: bytes, *, debug: bool=False) -> bytes:
if debug:
print(f"Compressed resource data header: {header_info}")
if isinstance(header_info, CompressedApplicationHeaderInfo):
decompress_func = _decompress_application
elif isinstance(header_info, CompressedSystemHeaderInfo):
decompress_func = _decompress_system
else:
raise DecompressError(f"Unsupported compression type: 0x{header_info.compression_type:>04x}")
try:
decompress_func = DECOMPRESSORS[header_info.dcmp_id]
except KeyError:
raise DecompressError(f"Unsupported 'dcmp' ID: {header_info.dcmp_id}")
decompressed = decompress_func(data[header_info.header_length:], header_info, debug=debug)
decompressed = decompress_func(header_info, data[header_info.header_length:], debug=debug)
if len(decompressed) != header_info.decompressed_length:
raise DecompressError(f"Actual length of decompressed data ({len(decompressed)}) does not match length stored in resource ({header_info.decompressed_length})")
return decompressed

5
rsrcfork/compress/dcmp0.py
View File

@ -36,9 +36,12 @@ TABLE = [TABLE_DATA[i:i + 2] for i in range(0, len(TABLE_DATA), 2)]
assert len(TABLE) == len(range(0x4b, 0xfe))
def decompress(header_info: common.CompressedApplicationHeaderInfo, data: bytes, *, debug: bool=False) -> bytes:
def decompress(header_info: common.CompressedHeaderInfo, data: bytes, *, debug: bool=False) -> bytes:
"""Decompress compressed data in the format used by 'dcmp' (0)."""
if not isinstance(header_info, common.CompressedApplicationHeaderInfo):
raise common.DecompressError(f"Incorrect header type: {type(header_info.__qualname__)}")
prev_literals = []
decompressed = b""

5
rsrcfork/compress/dcmp1.py
View File

@ -19,9 +19,12 @@ TABLE = [TABLE_DATA[i:i + 2] for i in range(0, len(TABLE_DATA), 2)]
assert len(TABLE) == len(range(0xd5, 0xfe))
def decompress(header_info: common.CompressedApplicationHeaderInfo, data: bytes, *, debug: bool=False) -> bytes:
def decompress(header_info: common.CompressedHeaderInfo, data: bytes, *, debug: bool=False) -> bytes:
"""Decompress compressed data in the format used by 'dcmp' (1)."""
if not isinstance(header_info, common.CompressedApplicationHeaderInfo):
raise common.DecompressError(f"Incorrect header type: {type(header_info.__qualname__)}")
prev_literals = []
decompressed = b""

5
rsrcfork/compress/dcmp2.py
View File

@ -131,9 +131,12 @@ def _decompress_system_tagged(data: bytes, decompressed_length: int, table: typi
return b"".join(parts)
def decompress(header_info: common.CompressedSystemHeaderInfo, data: bytes, *, debug: bool=False) -> bytes:
def decompress(header_info: common.CompressedHeaderInfo, data: bytes, *, debug: bool=False) -> bytes:
"""Decompress compressed data in the format used by 'dcmp' (2)."""
if not isinstance(header_info, common.CompressedSystemHeaderInfo):
raise common.DecompressError(f"Incorrect header type: {type(header_info.__qualname__)}")
unknown, table_count_m1, flags_raw = STRUCT_PARAMETERS.unpack(header_info.parameters)
if debug: