lib/util: add spdk_strlwr()

Add function to convert string to lowercase in place.

Originally based on code imported from istgt.

Change-Id: Ica9fe2208e6ee09b22c9a652a33c5affe5be23cc
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>

include/spdk/string.h

@@ -47,6 +47,13 @@ extern "C" {
  */
 char *spdk_sprintf_alloc(const char *format, ...) __attribute__((format(printf, 1, 2)));
 
+/**
+ * Convert string to lowercase in place.
+ *
+ * \param s String to convert to lowercase.
+ */
+char *spdk_strlwr(char *s);
+
 #ifdef __cplusplus
 }
 #endif

lib/util/string.c

@@ -1,6 +1,7 @@
 /*-
  *   BSD LICENSE
  *
+ *   Copyright (C) 2008-2012 Daisuke Aoyama <aoyama@peach.ne.jp>.
  *   Copyright (c) Intel Corporation.
  *   All rights reserved.
  *
@@ -34,6 +35,7 @@
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <ctype.h>
 
 #include "spdk/string.h"
 
@@ -80,3 +82,21 @@ spdk_sprintf_alloc(const char *format, ...)
 
 	return NULL;
 }
+
+char *
+spdk_strlwr(char *s)
+{
+	char *p;
+
+	if (s == NULL) {
+		return NULL;
+	}
+
+	p = s;
+	while (*p != '\0') {
+		*p = tolower(*p);
+		p++;
+	}
+
+	return s;
+}