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Change naming of compression types

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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.
This commit is contained in:
dgelessus 2019-10-07 10:08:32 +02:00
parent a71274d554
commit f3b3de496e
4 changed files with 24 additions and 24 deletions
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34
rsrcfork/compress/common.py
View File

@ -9,30 +9,30 @@ class DecompressError(Exception):
# 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
# The number of the "type 8" compression type. This type is used in the Finder, ResEdit, and some other system files.
COMPRESSED_TYPE_8 = 0x0801
# The number of the "type 9" compression type. This type is used in the System file and System 7.5's Installer.
COMPRESSED_TYPE_9 = 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.
# 2 bytes: Compression type. Known so far: 0x0801 ("type 8") and 0x0901 ("type 9").
# 4 bytes: Length of the data after decompression.
# 6 bytes: Remainder of the header. The exact format varies depending on the compression type.
STRUCT_COMPRESSED_HEADER = struct.Struct(">4sHHI6s")
# Remainder of header for an "application" compressed resource.
# Remainder of header for a "type 8" 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")
STRUCT_COMPRESSED_TYPE_8_HEADER = struct.Struct(">BBhH")
# Remainder of header for a "system" compressed resource.
# Remainder of header for a "type 9" 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")
STRUCT_COMPRESSED_TYPE_9_HEADER = struct.Struct(">h4s")
class CompressedHeaderInfo(object):
@ -47,17 +47,17 @@ class CompressedHeaderInfo(object):
if header_length != 0x12:
raise DecompressError(f"Unsupported header length: 0x{header_length:>04x}, expected 0x12")
if compression_type == COMPRESSED_TYPE_APPLICATION:
working_buffer_fractional_size, expansion_buffer_size, dcmp_id, reserved = STRUCT_COMPRESSED_APPLICATION_HEADER.unpack(remainder)
if compression_type == COMPRESSED_TYPE_8:
working_buffer_fractional_size, expansion_buffer_size, dcmp_id, reserved = STRUCT_COMPRESSED_TYPE_8_HEADER.unpack(remainder)
if reserved != 0:
raise DecompressError(f"Reserved field should be 0, not 0x{reserved:>04x}")
return CompressedApplicationHeaderInfo(header_length, compression_type, decompressed_length, dcmp_id, working_buffer_fractional_size, expansion_buffer_size)
elif compression_type == COMPRESSED_TYPE_SYSTEM:
dcmp_id, parameters = STRUCT_COMPRESSED_SYSTEM_HEADER.unpack(remainder)
return CompressedType8HeaderInfo(header_length, compression_type, decompressed_length, dcmp_id, working_buffer_fractional_size, expansion_buffer_size)
elif compression_type == COMPRESSED_TYPE_9:
dcmp_id, parameters = STRUCT_COMPRESSED_TYPE_9_HEADER.unpack(remainder)
return CompressedSystemHeaderInfo(header_length, compression_type, decompressed_length, dcmp_id, parameters)
return CompressedType9HeaderInfo(header_length, compression_type, decompressed_length, dcmp_id, parameters)
else:
raise DecompressError(f"Unsupported compression type: 0x{compression_type:>04x}")
@ -79,7 +79,7 @@ class CompressedHeaderInfo(object):
self.dcmp_id = dcmp_id
class CompressedApplicationHeaderInfo(CompressedHeaderInfo):
class CompressedType8HeaderInfo(CompressedHeaderInfo):
working_buffer_fractional_size: int
expansion_buffer_size: int
@ -93,7 +93,7 @@ class CompressedApplicationHeaderInfo(CompressedHeaderInfo):
return f"{type(self).__qualname__}(header_length={self.header_length}, compression_type=0x{self.compression_type:>04x}, decompressed_length={self.decompressed_length}, dcmp_id={self.dcmp_id}, working_buffer_fractional_size={self.working_buffer_fractional_size}, expansion_buffer_size={self.expansion_buffer_size})"
class CompressedSystemHeaderInfo(CompressedHeaderInfo):
class CompressedType9HeaderInfo(CompressedHeaderInfo):
parameters: bytes
def __init__(self, header_length: int, compression_type: int, decompressed_length: int, dcmp_id: int, parameters: bytes) -> None:

2
rsrcfork/compress/dcmp0.py
View File

@ -42,7 +42,7 @@ assert len(TABLE) == len(range(0x4b, 0xfe))
def decompress_stream_inner(header_info: common.CompressedHeaderInfo, stream: typing.BinaryIO, *, debug: bool=False) -> typing.Iterator[bytes]:
"""Internal helper function, implements the main decompression algorithm. Only called from decompress_stream, which performs some extra checks and debug logging."""
if not isinstance(header_info, common.CompressedApplicationHeaderInfo):
if not isinstance(header_info, common.CompressedType8HeaderInfo):
raise common.DecompressError(f"Incorrect header type: {type(header_info).__qualname__}")
prev_literals: typing.List[bytes] = []

2
rsrcfork/compress/dcmp1.py
View File

@ -25,7 +25,7 @@ assert len(TABLE) == len(range(0xd5, 0xfe))
def decompress_stream_inner(header_info: common.CompressedHeaderInfo, stream: typing.BinaryIO, *, debug: bool=False) -> typing.Iterator[bytes]:
"""Internal helper function, implements the main decompression algorithm. Only called from decompress_stream, which performs some extra checks and debug logging."""
if not isinstance(header_info, common.CompressedApplicationHeaderInfo):
if not isinstance(header_info, common.CompressedType8HeaderInfo):
raise common.DecompressError(f"Incorrect header type: {type(header_info).__qualname__}")
prev_literals: typing.List[bytes] = []

10
rsrcfork/compress/dcmp2.py
View File

@ -74,7 +74,7 @@ def _split_bits(i: int) -> typing.Tuple[bool, bool, bool, bool, bool, bool, bool
)
def _decompress_system_untagged(stream: "common.PeekableIO", decompressed_length: int, table: typing.Sequence[bytes], *, debug: bool=False) -> typing.Iterator[bytes]:
def _decompress_untagged(stream: "common.PeekableIO", decompressed_length: int, table: typing.Sequence[bytes], *, debug: bool=False) -> typing.Iterator[bytes]:
while True: # Loop is terminated when EOF is reached.
table_index_data = stream.read(1)
if not table_index_data:
@ -93,7 +93,7 @@ def _decompress_system_untagged(stream: "common.PeekableIO", decompressed_length
print(f"Reference: {table_index} -> {table[table_index]}")
yield table[table_index]
def _decompress_system_tagged(stream: "common.PeekableIO", decompressed_length: int, table: typing.Sequence[bytes], *, debug: bool=False) -> typing.Iterator[bytes]:
def _decompress_tagged(stream: "common.PeekableIO", decompressed_length: int, table: typing.Sequence[bytes], *, debug: bool=False) -> typing.Iterator[bytes]:
while True: # Loop is terminated when EOF is reached.
tag_data = stream.read(1)
if not tag_data:
@ -136,7 +136,7 @@ def _decompress_system_tagged(stream: "common.PeekableIO", decompressed_length:
def decompress_stream(header_info: common.CompressedHeaderInfo, stream: typing.BinaryIO, *, debug: bool=False) -> typing.Iterator[bytes]:
"""Decompress compressed data in the format used by 'dcmp' (2)."""
if not isinstance(header_info, common.CompressedSystemHeaderInfo):
if not isinstance(header_info, common.CompressedType9HeaderInfo):
raise common.DecompressError(f"Incorrect header type: {type(header_info).__qualname__}")
unknown, table_count_m1, flags_raw = STRUCT_PARAMETERS.unpack(header_info.parameters)
@ -170,8 +170,8 @@ def decompress_stream(header_info: common.CompressedHeaderInfo, stream: typing.B
print("Using default table")
if ParameterFlags.TAGGED in flags:
decompress_func = _decompress_system_tagged
decompress_func = _decompress_tagged
else:
decompress_func = _decompress_system_untagged
decompress_func = _decompress_untagged
yield from decompress_func(common.make_peekable(stream), header_info.decompressed_length, table, debug=debug)