Make the generic decompression API stream-based

The non-stream-based APIs still exist as before and are not deprecated,
they just act as thin wrappers around the stream-based API.

The main rsrcfork module doesn't use the stream-based APIs yet, because
it reads each resource's data all at once and not incrementally.

rsrcfork/compress/__init__.py

@@ -1,3 +1,6 @@
+import io
+import typing
+
 from . import dcmp0
 from . import dcmp1
 from . import dcmp2
@@ -11,34 +14,46 @@ __all__ = [
 
 
 # Maps 'dcmp' IDs to their corresponding Python implementations.
-# Each decompressor has the signature (header_info: CompressedHeaderInfo, data: bytes, *, debug: bool=False) -> bytes.
+# Each decompressor has the signature (header_info: CompressedHeaderInfo, stream: typing.BinaryIO, *, debug: bool=False) -> typing.Iterator[bytes].
 DECOMPRESSORS = {
-	0: dcmp0.decompress,
-	1: dcmp1.decompress,
-	2: dcmp2.decompress,
+	0: dcmp0.decompress_stream,
+	1: dcmp1.decompress_stream,
+	2: dcmp2.decompress_stream,
 }
 
 
-def decompress_parsed(header_info: CompressedHeaderInfo, data: bytes, *, debug: bool=False) -> bytes:
-	"""Decompress the given compressed resource data, whose header has already been removed and parsed into a CompressedHeaderInfo object."""
+def decompress_stream_parsed(header_info: CompressedHeaderInfo, stream: typing.BinaryIO, *, debug: bool=False) -> typing.Iterator[bytes]:
+	"""Decompress compressed resource data from a stream, whose header has already been read and parsed into a CompressedHeaderInfo object."""
 	
 	try:
 		decompress_func = DECOMPRESSORS[header_info.dcmp_id]
 	except KeyError:
 		raise DecompressError(f"Unsupported 'dcmp' ID: {header_info.dcmp_id}")
 	
-	decompressed = decompress_func(header_info, data, 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
-
-
-def decompress(data: bytes, *, debug: bool=False) -> bytes:
-	"""Decompress the given compressed resource data."""
+	decompressed_length = 0
+	for chunk in decompress_func(header_info, stream, debug=debug):
+		decompressed_length += len(chunk)
+		yield chunk
 	
-	header_info = CompressedHeaderInfo.parse(data)
+	if decompressed_length != header_info.decompressed_length:
+		raise DecompressError(f"Actual length of decompressed data ({decompressed_length}) does not match length stored in resource ({header_info.decompressed_length})")
+
+def decompress_parsed(header_info: CompressedHeaderInfo, data: bytes, *, debug: bool=False) -> bytes:
+	"""Decompress the given compressed resource data, whose header has already been removed and parsed into a CompressedHeaderInfo object."""
+	
+	return b"".join(decompress_stream_parsed(header_info, io.BytesIO(data), debug=debug))
+
+def decompress_stream(stream: typing.BinaryIO, *, debug: bool=False) -> typing.Iterator[bytes]:
+	"""Decompress compressed resource data from a stream."""
+	
+	header_info = CompressedHeaderInfo.parse_stream(stream)
 	
 	if debug:
 		print(f"Compressed resource data header: {header_info}")
 	
-	return decompress_parsed(header_info, data[header_info.header_length:], debug=debug)
+	yield from decompress_stream_parsed(header_info, stream, debug=debug)
+
+def decompress(data: bytes, *, debug: bool=False) -> bytes:
+	"""Decompress the given compressed resource data."""
+	
+	return b"".join(decompress_stream(io.BytesIO(data), debug=debug))

rsrcfork/compress/common.py

@@ -37,9 +37,9 @@ STRUCT_COMPRESSED_SYSTEM_HEADER = struct.Struct(">h4s")
 
 class CompressedHeaderInfo(object):
 	@classmethod
-	def parse(cls, data: bytes) -> "CompressedHeaderInfo":
+	def parse_stream(cls, stream: typing.BinaryIO) -> "CompressedHeaderInfo":
 		try:
-			signature, header_length, compression_type, decompressed_length, remainder = STRUCT_COMPRESSED_HEADER.unpack_from(data)
+			signature, header_length, compression_type, decompressed_length, remainder = STRUCT_COMPRESSED_HEADER.unpack(stream.read(STRUCT_COMPRESSED_HEADER.size))
 		except struct.error:
 			raise DecompressError(f"Invalid header")
 		if signature != COMPRESSED_SIGNATURE:
@@ -61,6 +61,10 @@ class CompressedHeaderInfo(object):
 		else:
 			raise DecompressError(f"Unsupported compression type: 0x{compression_type:>04x}")
 	
+	@classmethod
+	def parse(cls, data: bytes) -> "CompressedHeaderInfo":
+		return cls.parse_stream(io.BytesIO(data))
+	
 	header_length: int
 	compression_type: int
 	decompressed_length: int

rsrcfork/compress/dcmp0.py

@@ -267,6 +267,3 @@ def decompress_stream(header_info: common.CompressedHeaderInfo, stream: typing.B
 		
 		if debug:
 			print(f"Decompressed {decompressed_length:#x} bytes so far")
-
-def decompress(header_info: common.CompressedHeaderInfo, data: bytes, *, debug: bool=False) -> bytes:
-	return b"".join(decompress_stream(header_info, io.BytesIO(data), debug=debug))

rsrcfork/compress/dcmp1.py

@@ -142,6 +142,3 @@ def decompress_stream(header_info: common.CompressedHeaderInfo, stream: typing.B
 		
 		if debug:
 			print(f"Decompressed {decompressed_length:#x} bytes so far")
-
-def decompress(header_info: common.CompressedHeaderInfo, data: bytes, *, debug: bool=False) -> bytes:
-	return b"".join(decompress_stream(header_info, io.BytesIO(data), debug=debug))

rsrcfork/compress/dcmp2.py

@@ -175,6 +175,3 @@ def decompress_stream(header_info: common.CompressedHeaderInfo, stream: typing.B
 		decompress_func = _decompress_system_untagged
 	
 	yield from decompress_func(common.make_peekable(stream), header_info.decompressed_length, table, debug=debug)
-
-def decompress(header_info: common.CompressedHeaderInfo, data: bytes, *, debug: bool=False) -> bytes:
-	return b"".join(decompress_stream(header_info, io.BytesIO(data), debug=debug))