stringop: Add is_empty() for checking for empty strings

common/stringop.c

@@ -293,6 +293,24 @@ static bool has_whitespace(const char *str) {
 	return false;
 }
 
+
+/*
+ * Returns true if the string contains only whitespace and false otherwise.
+ */
+bool is_empty(const char *str) {
+	bool ret = true;
+	if (str) {
+		while (*str != '\0') {
+			if (!isspace(*(const unsigned char*)str)) {
+				ret = false;
+				break;
+			}
+			str++;
+		}
+	}
+	return ret;
+}
+
 /**
  * Add quotes around any argv with whitespaces.
  */

include/stringop.h

@@ -1,5 +1,7 @@
 #ifndef _SWAY_STRINGOP_H
 #define _SWAY_STRINGOP_H
+
+#include <stdbool.h>
 #include "list.h"
 
 #if !HAVE_DECL_SETENV
@@ -14,6 +16,9 @@ void strip_whitespace(char *str);
 char *strip_comments(char *str);
 void strip_quotes(char *str);
 
+// Returns true if the string contains only whitespace.
+bool is_empty(const char *str);
+
 // strcmp that also handles null pointers.
 int lenient_strcmp(char *a, char *b);