Minimal module to decode AppleSingle files (the way resource files are

stored in the CVS repository). It can either decode resource/data forks
in the standard Mac way or decode only the resource fork but store
the result in the data fork (the MacOSX preferred way). Finder info
and all other stuff is ignored.

Mac/Lib/applesingle.py

@@ -0,0 +1,101 @@
+# applesingle - a module to decode AppleSingle files
+import struct
+import MacOS
+import sys
+
+Error="applesingle.Error"
+
+verbose=0
+
+# File header format: magic, version, unused, number of entries
+AS_HEADER_FORMAT="ll16sh"
+AS_HEADER_LENGTH=26
+# The flag words for AppleSingle
+AS_MAGIC=0x00051600
+AS_VERSION=0x00020000
+
+# Entry header format: id, offset, length
+AS_ENTRY_FORMAT="lll"
+AS_ENTRY_LENGTH=12
+
+# The id values
+AS_DATAFORK=1
+AS_RESOURCEFORK=2
+AS_IGNORE=(3,4,5,6,8,9,10,11,12,13,14,15)
+
+def decode(input, output, resonly=0):
+	if type(input) == type(''):
+		input = open(input, 'rb')
+	# Should we also test for FSSpecs or FSRefs?
+	header = input.read(AS_HEADER_LENGTH)
+	print `header`
+	try:
+		magic, version, dummy, nentry = struct.unpack(AS_HEADER_FORMAT, header)
+	except ValueError, arg:
+		raise Error, "Unpack header error: %s"%arg
+	if verbose:
+		print 'Magic:   0x%8.8x'%magic
+		print 'Version: 0x%8.8x'%version
+		print 'Entries: %d'%nentry
+	if magic != AS_MAGIC:
+		raise Error, 'Unknown AppleSingle magic number 0x%8.8x'%magic
+	if version != AS_VERSION:
+		raise Error, 'Unknown AppleSingle version number 0x%8.8x'%version
+	if nentry <= 0:
+		raise Error, "AppleSingle file contains no forks"
+	headers = [input.read(AS_ENTRY_LENGTH) for i in range(nentry)]
+	didwork = 0
+	for hdr in headers:
+		try:
+			id, offset, length = struct.unpack(AS_ENTRY_FORMAT, hdr)
+		except ValueError, arg:
+			raise Error, "Unpack entry error: %s"%arg
+		if verbose:
+			print 'Fork %d, offset %d, length %d'%(id, offset, length)
+		input.seek(offset)
+		if length == 0:
+			data = ''
+		else:
+			data = input.read(length)
+		if len(data) != length:
+			raise Error, 'Short read: expected %d bytes got %d'%(length, len(data))
+		if id == AS_DATAFORK:
+			if verbose:
+				print '  (data fork)'
+			if not resonly:
+				didwork = 1
+				fp = open(output, 'wb')
+				fp.write(data)
+				fp.close()
+		elif id == AS_RESOURCEFORK:
+			didwork = 1
+			if verbose:
+				print '  (resource fork)'
+			if resonly:
+				fp = open(output, 'wb')
+			else:
+				fp = MacOS.openrf(output, 'wb')
+			fp.write(data)
+			fp.close()
+		elif id in AS_IGNORE:
+			if verbose:
+				print '  (ignored)'
+		else:
+			raise Error, 'Unknown fork type %d'%id
+	if not didwork:
+		raise Error, 'No useful forks found'
+
+def _test():
+	if len(sys.argv) < 3 or sys.argv[1] == '-r' and len(sys.argv) != 4:
+		print 'Usage: applesingle.py [-r] applesinglefile decodedfile'
+		sys.exit(1)
+	if sys.argv[1] == '-r':
+		resonly = 1
+		del sys.argv[1]
+	else:
+		resonly = 0
+	decode(sys.argv[1], sys.argv[2], resonly=resonly)
+	
+if __name__ == '__main__':
+	_test()
+