Addes {string-len} macros to calculate string length

src/binwalk/__init__.py

@@ -550,6 +550,8 @@ class Binwalk(object):
 
 						i_set_results_offset = False
 
+						magic_result = self.smart._parse_string_len(magic_result)
+
 						# Some file names are not NULL byte terminated, but rather their length is
 						# specified in a size field. To ensure these are not marked as invalid due to
 						# non-printable characters existing in the file name, parse the filename(s) and

src/binwalk/smartsignature.py

@@ -22,6 +22,7 @@ class SmartSignature:
 		'filename'		: '%sfile-name:' % KEYWORD_DELIM_START,
 		'filesize'		: '%sfile-size:' % KEYWORD_DELIM_START,
 		'raw-string'		: '%sraw-string:' % KEYWORD_DELIM_START,	# This one is special and must come last in a signature block
+		'string-len'		: '%sstring-len:' % KEYWORD_DELIM_START,
 		'raw-size'		: '%sraw-string-length:' % KEYWORD_DELIM_START,
 		'adjust'		: '%soffset-adjust:' % KEYWORD_DELIM_START,
 		'delay'			: '%sextract-delay:' % KEYWORD_DELIM_START,
@@ -240,6 +241,27 @@ class SmartSignature:
 					# marked as invalid when it shouldn't be.
 					data = data[:data.find(self.KEYWORDS['raw-string'])].replace(self.KEYWORDS['raw-replace'], '"' + raw_string[:str2int(raw_size)] + '"')
 		return data
+		
+	def _parse_string_len(self, data):
+		'''
+		Process {string-len} macros. 
+
+		@data - String to parse.
+
+		Returns strings length.
+		'''
+		if not self.ignore_smart_signatures and self._is_valid(data):
+			# Get the raw string  keyword arg
+			raw_string = self._get_keyword_arg(data, 'string-len')
+
+			# Was a string-len  keyword specified?
+			if raw_string:				
+				# Is the raw string  length arg is a numeric value?
+				
+				# Replace all instances of string-len in data with supplied string lenth
+				# Also strip out everything after the string-len keyword, including the keyword itself.
+				data = re.sub(self.KEYWORDS['string-len']+".+?%s" % self.KEYWORD_DELIM_END, str(len(raw_string)),data)
+		return data
 
 	def _strip_tags(self, data):
 		'''