util: add string-util.[ch]

This is to give a home to strtok_len. It's a bit silly to add a header
for one routine, but it needs to be shared between several compilation
units (or at least that's the most natural design).

util/Makefile.local

@@ -3,7 +3,8 @@
 dir := util
 extra_cflags += -I$(srcdir)/$(dir)
 
-libutil_c_srcs := $(dir)/xutil.c $(dir)/error_util.c $(dir)/hex-escape.c
+libutil_c_srcs := $(dir)/xutil.c $(dir)/error_util.c $(dir)/hex-escape.c \
+		  $(dir)/string-util.c
 
 libutil_modules := $(libutil_c_srcs:.c=.o)
 

util/string-util.c

@@ -0,0 +1,34 @@
+/* string-util.c -  Extra or enhanced routines for null terminated strings.
+ *
+ * Copyright (c) 2012 Jani Nikula
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see http://www.gnu.org/licenses/ .
+ *
+ * Author: Jani Nikula <jani@nikula.org>
+ */
+
+
+#include "string-util.h"
+
+char *
+strtok_len (char *s, const char *delim, size_t *len)
+{
+    /* skip initial delims */
+    s += strspn (s, delim);
+
+    /* length of token */
+    *len = strcspn (s, delim);
+
+    return *len ? s : NULL;
+}

util/string-util.h

@@ -0,0 +1,22 @@
+#ifndef _STRING_UTIL_H
+#define _STRING_UTIL_H
+
+#include <string.h>
+
+/* like strtok(3), but without state, and doesn't modify s.  Return
+ * value is indicated by pointer and length, not null terminator.
+ *
+ * Usage pattern:
+ *
+ * const char *tok = input;
+ * const char *delim = " \t";
+ * size_t tok_len = 0;
+ *
+ * while ((tok = strtok_len (tok + tok_len, delim, &tok_len)) != NULL) {
+ *     // do stuff with string tok of length tok_len
+ * }
+ */
+
+char *strtok_len (char *s, const char *delim, size_t *len);
+
+#endif