Split out is_printable_string() into util.c

This useful function is split out so it will be available to programs
other than ftdump.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: David Gibson <david@gibson.dropbear.id.au>

util.c

@@ -1,6 +1,9 @@
 /*
  * Copyright 2008 Jon Loeliger, Freescale Semiconductor, Inc.
  *
+ * util_is_printable_string contributed by
+ *	Pantelis Antoniou <pantelis.antoniou AT gmail.com>
+ *
  * 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 2 of the
@@ -17,6 +20,7 @@
  *                                                                   USA
  */
 
+#include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
@@ -57,3 +61,27 @@ char *join_path(const char *path, const char *name)
 	memcpy(str+lenp, name, lenn+1);
 	return str;
 }
+
+int util_is_printable_string(const void *data, int len)
+{
+	const char *s = data;
+	const char *ss;
+
+	/* zero length is not */
+	if (len == 0)
+		return 0;
+
+	/* must terminate with zero */
+	if (s[len - 1] != '\0')
+		return 0;
+
+	ss = s;
+	while (*s && isprint(*s))
+		s++;
+
+	/* not zero, or not done yet */
+	if (*s != '\0' || (s + 1 - ss) < len)
+		return 0;
+
+	return 1;
+}