begin work on new lexer

subprojects/libutf/utfrune.c

@@ -0,0 +1,44 @@
+/*
+ * The authors of this software are Rob Pike and Ken Thompson.
+ *              Copyright (c) 2002 by Lucent Technologies.
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose without fee is hereby granted, provided that this entire notice
+ * is included in all copies of any software which is or includes a copy
+ * or modification of this software and in all copies of the supporting
+ * documentation for such software.
+ * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
+ * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE
+ * ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
+ * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
+ */
+#include <stdarg.h>
+#include <string.h>
+#include "plan9.h"
+#include "utf.h"
+
+char*
+utfrune(char *s, long c)
+{
+	long c1;
+	Rune r;
+	int n;
+
+	if(c < Runesync)		/* not part of utf sequence */
+		return strchr(s, c);
+
+	for(;;) {
+		c1 = *(uchar*)s;
+		if(c1 < Runeself) {	/* one byte rune */
+			if(c1 == 0)
+				return 0;
+			if(c1 == c)
+				return s;
+			s++;
+			continue;
+		}
+		n = chartorune(&r, s);
+		if(r == c)
+			return s;
+		s += n;
+	}
+}