Clean up Strfnd

Changes:
  * Fix indentation.
  * Pass strings by const reference.
  * Merge Strfnd and WStrfnd into one class instead of copying them.
  * Remove trailing spaces.
  * Fix variable names.
  * Move to util.
  * Other miscellaneous style fixes.

src/util/strfnd.h

@@ -0,0 +1,82 @@
+/*
+Minetest
+Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#ifndef STRFND_HEADER
+#define STRFND_HEADER
+
+#include <string>
+
+template <typename T>
+class BasicStrfnd {
+	typedef std::basic_string<T> String;
+	String str;
+	size_t pos;
+public:
+	BasicStrfnd(const String &s) : str(s), pos(0) {}
+	void start(const String &s) { str = s; pos = 0; }
+	size_t where() { return pos; }
+	void to(size_t i) { pos = i; }
+	bool at_end() { return pos >= str.size(); }
+	String what() { return str; }
+
+	String next(const String &sep)
+	{
+		if (pos >= str.size())
+			return String();
+
+		size_t n;
+		if (sep.empty() || (n = str.find(sep, pos)) == String::npos) {
+			n = str.size();
+		}
+		String ret = str.substr(pos, n - pos);
+		pos = n + sep.size();
+		return ret;
+	}
+
+	// Returns substr up to the next occurence of sep that isn't escaped with esc ('\\')
+	String next_esc(const String &sep, T esc=static_cast<T>('\\'))
+	{
+		if (pos >= str.size())
+			return String();
+
+		size_t n, old_p = pos;
+		do {
+			if (sep.empty() || (n = str.find(sep, pos)) == String::npos) {
+				pos = n = str.size();
+				break;
+			}
+			pos = n + sep.length();
+		} while (n > 0 && str[n - 1] == esc);
+
+		return str.substr(old_p, n - old_p);
+	}
+
+	void skip_over(const String &chars)
+	{
+		size_t p = str.find_first_not_of(chars, pos);
+		if (p != String::npos)
+			pos = p;
+	}
+};
+
+typedef BasicStrfnd<char> Strfnd;
+typedef BasicStrfnd<wchar_t> WStrfnd;
+
+#endif
+