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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 dcmp1
from . import dcmp2
from .common import DecompressError
from .common import DecompressError, CompressedApplicationHeaderInfo, CompressedHeaderInfo, CompressedSystemHeaderInfo
__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.
# 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:
if header_info.dcmp_id == 0:

85
rsrcfork/compress/common.py
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@ -1,3 +1,4 @@
import struct
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."""
# 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]:
"""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.