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Move compressed header info constants/classes to .compress.common

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This allows the constants/classes to be accessed from the individual
decompressor submodules.
This commit is contained in:
dgelessus 2019-09-23 23:14:06 +02:00
parent 87d4ae43d4
commit 9dbdf5b827
2 changed files with 86 additions and 86 deletions
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87
rsrcfork/compress/__init__.py
View File

@ -1,99 +1,14 @@
import struct
from . import dcmp0 from . import dcmp0
from . import dcmp1 from . import dcmp1
from . import dcmp2 from . import dcmp2
from .common import DecompressError from .common import DecompressError, CompressedApplicationHeaderInfo, CompressedHeaderInfo, CompressedSystemHeaderInfo
__all__ = [ __all__ = [
"DecompressError", "DecompressError",
"decompress", "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.
# 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.
# 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")
# Remainder of header 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")
class CompressedHeaderInfo(object):
@classmethod
def parse(cls, data: bytes) -> "CompressedHeaderInfo":
try:
signature, header_length, compression_type, decompressed_length, remainder = 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:
working_buffer_fractional_size, expansion_buffer_size, dcmp_id, reserved = STRUCT_COMPRESSED_APPLICATION_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 CompressedSystemHeaderInfo(header_length, compression_type, decompressed_length, dcmp_id, parameters)
else:
raise DecompressError(f"Unsupported compression type: 0x{compression_type:>04x}")
def __init__(self, header_length: int, compression_type: int, decompressed_length: int, dcmp_id: int) -> None:
super().__init__()
self.header_length: int = header_length
self.compression_type: int = compression_type
self.decompressed_length: int = decompressed_length
self.dcmp_id: int = dcmp_id
class CompressedApplicationHeaderInfo(CompressedHeaderInfo):
def __init__(self, header_length: int, compression_type: int, decompressed_length: int, dcmp_id: int, working_buffer_fractional_size: int, expansion_buffer_size: int) -> None:
super().__init__(header_length, compression_type, decompressed_length, dcmp_id)
self.working_buffer_fractional_size: int = working_buffer_fractional_size
self.expansion_buffer_size: int = expansion_buffer_size
def __repr__(self):
return f"{type(self).__qualname__}(header_length={self.header_length}, compression_type={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):
def __init__(self, header_length: int, compression_type: int, decompressed_length: int, dcmp_id: int, parameters: bytes) -> None:
super().__init__(header_length, compression_type, decompressed_length, dcmp_id)
self.parameters: bytes = parameters
def __repr__(self):
return f"{type(self).__qualname__}(header_length={self.header_length}, compression_type={self.compression_type:>04x}, decompressed_length={self.decompressed_length}, dcmp_id={self.dcmp_id}, parameters={self.parameters!r})"
def _decompress_application(data: bytes, header_info: CompressedApplicationHeaderInfo, *, debug: bool=False) -> bytes: def _decompress_application(data: bytes, header_info: CompressedApplicationHeaderInfo, *, debug: bool=False) -> bytes:
if header_info.dcmp_id == 0: if header_info.dcmp_id == 0:

85
rsrcfork/compress/common.py
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@ -1,3 +1,4 @@
import struct
import typing import typing
@ -5,6 +6,90 @@ class DecompressError(Exception):
"""Raised when resource data decompression fails, because the data is invalid or the compression type is not supported.""" """Raised when resource data decompression fails, because the data is invalid or the compression type is not supported."""
# 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.
# 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.
# 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")
# Remainder of header 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")
class CompressedHeaderInfo(object):
@classmethod
def parse(cls, data: bytes) -> "CompressedHeaderInfo":
try:
signature, header_length, compression_type, decompressed_length, remainder = 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:
working_buffer_fractional_size, expansion_buffer_size, dcmp_id, reserved = STRUCT_COMPRESSED_APPLICATION_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 CompressedSystemHeaderInfo(header_length, compression_type, decompressed_length, dcmp_id, parameters)
else:
raise DecompressError(f"Unsupported compression type: 0x{compression_type:>04x}")
def __init__(self, header_length: int, compression_type: int, decompressed_length: int, dcmp_id: int) -> None:
super().__init__()
self.header_length: int = header_length
self.compression_type: int = compression_type
self.decompressed_length: int = decompressed_length
self.dcmp_id: int = dcmp_id
class CompressedApplicationHeaderInfo(CompressedHeaderInfo):
def __init__(self, header_length: int, compression_type: int, decompressed_length: int, dcmp_id: int, working_buffer_fractional_size: int, expansion_buffer_size: int) -> None:
super().__init__(header_length, compression_type, decompressed_length, dcmp_id)
self.working_buffer_fractional_size: int = working_buffer_fractional_size
self.expansion_buffer_size: int = expansion_buffer_size
def __repr__(self):
return f"{type(self).__qualname__}(header_length={self.header_length}, compression_type={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):
def __init__(self, header_length: int, compression_type: int, decompressed_length: int, dcmp_id: int, parameters: bytes) -> None:
super().__init__(header_length, compression_type, decompressed_length, dcmp_id)
self.parameters: bytes = parameters
def __repr__(self):
return f"{type(self).__qualname__}(header_length={self.header_length}, compression_type={self.compression_type:>04x}, decompressed_length={self.decompressed_length}, dcmp_id={self.dcmp_id}, parameters={self.parameters!r})"
def _read_variable_length_integer(data: bytes, position: int) -> typing.Tuple[int, int]: 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. """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.