diff --git a/Frameworks/regexp/src/format_string.cc b/Frameworks/regexp/src/format_string.cc
index d142586d..7b9f97bf 100644
--- a/Frameworks/regexp/src/format_string.cc
+++ b/Frameworks/regexp/src/format_string.cc
@@ -266,10 +266,10 @@ namespace format_string
 		nodes.reset(new parser::nodes_t(n));
 	}
 
-	void format_string_t::init (std::string const& str)
+	void format_string_t::init (std::string const& str, char const* stopChars)
 	{
 		D(DBF_FormatString, bug("%s\n", str.c_str()););
-		parser::nodes_t const& n = parser::parse_format_string(str);
+		parser::nodes_t const& n = parser::parse_format_string(str, stopChars, &_length);
 		nodes.reset(new parser::nodes_t(n));
 	}
 	
diff --git a/Frameworks/regexp/src/format_string.h b/Frameworks/regexp/src/format_string.h
index a25c8f97..6255e76a 100644
--- a/Frameworks/regexp/src/format_string.h
+++ b/Frameworks/regexp/src/format_string.h
@@ -11,18 +11,21 @@ namespace format_string
 	{
 		WATCH_LEAKS(format_string::format_string_t);
 
-		format_string_t (char const* str = "")   { init(str); }
-		format_string_t (std::string const& str) { init(str); }
+		format_string_t (char const* str = "", char const* stopChars = "")   { init(str, stopChars); }
+		format_string_t (std::string const& str, char const* stopChars = "") { init(str, stopChars); }
 		
 		format_string_t (parser::nodes_t const& nodes);
 		std::string expand (std::map<std::string, std::string> const& variables) const;
 
+		size_t length () const { return _length; }
+
 	private:
 		friend std::string replace (std::string const& src, regexp::pattern_t const& ptrn, format_string_t const& format, bool repeat, std::map<std::string, std::string> const& variables);
 		friend std::set<std::string> get_variables (format_string_t const&);
 
-		void init (std::string const& str);
+		void init (std::string const& str, char const* stopChars);
 		std::shared_ptr<parser::nodes_t> nodes;
+		size_t _length = 0;
 	};
 
 	PUBLIC std::string replace (std::string const& src, regexp::pattern_t const& ptrn, format_string_t const& format, bool repeat = true, std::map<std::string, std::string> const& variables = std::map<std::string, std::string>());
diff --git a/Frameworks/regexp/src/parser.cc b/Frameworks/regexp/src/parser.cc
index 30790154..ebd5f617 100644
--- a/Frameworks/regexp/src/parser.cc
+++ b/Frameworks/regexp/src/parser.cc
@@ -387,11 +387,13 @@ bool parse_context_t::parse_snippet (char const* stopChars, nodes_t& nodes)
 // = API Functions =
 // =================
 
-nodes_t parse_format_string (std::string const& str)
+nodes_t parse_format_string (std::string const& str, char const* stopChars, size_t* length)
 {
 	parse_context_t context(str);
 	nodes_t nodes;
-	context.parse_format_string("", nodes);
+	context.parse_format_string(stopChars, nodes);
+	if(length)
+		*length = context.bytes_parsed();
 	return nodes;
 }
 
diff --git a/Frameworks/regexp/src/parser.h b/Frameworks/regexp/src/parser.h
index cfe9d77f..0f97f409 100644
--- a/Frameworks/regexp/src/parser.h
+++ b/Frameworks/regexp/src/parser.h
@@ -28,7 +28,7 @@ namespace parser
 
 	OnigOptionType convert (regexp_options::type const& options);
 
-	nodes_t parse_format_string (std::string const& str);
+	nodes_t parse_format_string (std::string const& str, char const* stopChars = "", size_t* length = nullptr);
 	nodes_t parse_snippet (std::string const& str);
 
 } /* parser */ 
diff --git a/Frameworks/regexp/src/parser_base.cc b/Frameworks/regexp/src/parser_base.cc
index ae1701ef..0da6484d 100644
--- a/Frameworks/regexp/src/parser_base.cc
+++ b/Frameworks/regexp/src/parser_base.cc
@@ -2,8 +2,8 @@
 
 parser_base_t::parser_base_t (std::string const& str)
 {
-	it   = str.data();
-	last = str.data() + str.size();
+	first = it = str.data();
+	last = first + str.size();
 }
 
 bool parser_base_t::parse_char (char const* ch)
diff --git a/Frameworks/regexp/src/parser_base.h b/Frameworks/regexp/src/parser_base.h
index f853e11d..3c45f9e3 100644
--- a/Frameworks/regexp/src/parser_base.h
+++ b/Frameworks/regexp/src/parser_base.h
@@ -10,7 +10,10 @@ struct parser_base_t
 	bool parse_int (size_t& res);
 	bool parse_until (char const* stopChars, std::string& res);
 
+	size_t bytes_parsed () const { return it - first; }
+
 protected:
+	char const* first;
 	char const* it;
 	char const* last;
 };