Made utils::escape/unescape not modify their argument.

src/dialogs.cpp

@@ -437,8 +437,7 @@ void save_preview_pane::draw_contents()
 	std::stringstream str;
 
 	// Escape all special characters in filenames
-	std::string name = (*info_)[index_].name;
-	str << font::BOLD_TEXT << utils::escape(name) << "\n" << time_buf;
+	str << font::BOLD_TEXT << utils::escape((*info_)[index_].name) << '\n' << time_buf;
 
 	const std::string& campaign_type = summary["campaign_type"];
 	if(utils::string_bool(summary["corrupt"], false)) {

src/marked-up_text.cpp

@@ -211,9 +211,7 @@ SDL_Rect draw_text(surface dst, const SDL_Rect& area, int size,
 		i1 = parse_markup(i1,i2,&sz,&col,&text_style);
 
 		if(i1 != i2) {
-			std::string new_string(i1,i2);
-
-			utils::unescape(new_string);
+			std::string new_string = utils::unescape(std::string(i1, i2));
 
 			const SDL_Rect rect = draw_text_line(dst, area, sz, col, new_string, x, y, use_tooltips, text_style);
 			if(rect.w > res.w) {

src/serialization/preprocessor.cpp

@@ -463,10 +463,9 @@ preprocessor_data::preprocessor_data(preprocessor_streambuf &t,
 
 	s << history;
 	if (!name.empty()) {
-		std::string ename(name);
 		if (!history.empty())
 			s << ' ';
-		s << utils::escape(ename, " \\");
+		s << utils::escape(name, " \\");
 	}
 	if (!t.location_.empty())
 		s << ' ' << t.linenum_ << ' ' << t.location_;

src/serialization/string_utils.cpp

@@ -207,35 +207,33 @@ int apply_modifier( const int number, const std::string &amount, const int minim
 	return value;
 }
 
-std::string &escape(std::string &str, const std::string& special_chars)
+std::string escape(const std::string &str, const char *special_chars)
 {
-	std::string::size_type pos = 0;
+	std::string::size_type pos = str.find_first_of(special_chars);
+	if (pos == std::string::npos) {
+		// Fast path, possibly involving only reference counting.
+		return str;
+	}
+	std::string res = str;
 	do {
-		pos = str.find_first_of(special_chars, pos);
-		if (pos == std::string::npos)
-			break;
-		str.insert(pos, 1, '\\');
-		pos += 2;
-	} while (pos < str.size());
-	return str;
+		res.insert(pos, 1, '\\');
+		pos = res.find_first_of(special_chars, pos + 2);
+	} while (pos != std::string::npos);
+	return res;
 }
 
-std::string& escape(std::string& str)
+std::string unescape(const std::string &str)
 {
-	static const std::string special_chars("#@{}+-,\\*=");
-	return escape(str, special_chars);
-}
-
-std::string &unescape(std::string &str)
-{
-	std::string::size_type pos = 0;
+	std::string::size_type pos = str.find('\\');
+	if (pos == std::string::npos) {
+		// Fast path, possibly involving only reference counting.
+		return str;
+	}
+	std::string res = str;
 	do {
-		pos = str.find('\\', pos);
-		if (pos == std::string::npos)
-			break;
-		str.erase(pos, 1);
-		++pos;
-	} while (pos < str.size());
+		res.erase(pos, 1);
+		pos = res.find('\\', pos + 1);
+	} while (pos != std::string::npos);
 	return str;
 }
 

src/serialization/string_utils.hpp

@@ -109,7 +109,7 @@ std::vector< std::pair< int, int > > parse_ranges(std::string const &str);
 int apply_modifier( const int number, const std::string &amount, const int minimum = 0);
 
 /** Prepends a configurable set of characters with a backslash */
-std::string &escape(std::string &str, const std::string& special_chars);
+std::string escape(const std::string &str, const char *special_chars);
 
 /**
  * Prepend all special characters with a backslash.
@@ -117,10 +117,11 @@ std::string &escape(std::string &str, const std::string& special_chars);
  * Special characters are:
  * #@{}+-,\*=
  */
-std::string &escape(std::string &str);
+inline std::string escape(const std::string &str)
+{ return escape(str, "#@{}+-,\\*="); }
 
 /** Remove all escape characters (backslash) */
-std::string &unescape(std::string &str);
+std::string unescape(const std::string &str);
 
 /** Remove whitespace from the front and back of the string 'str'. */
 std::string &strip(std::string &str);