feat: (str) str_is_blank

lib/inc/str.h

@@ -28,5 +28,6 @@ bool str_ends_with (const str_t *str, const char *find); /* check if a str_t str
 bool str_ends_with_len (const str_t *str, const char *find, size_t len); /* check if a str_t string ends with a cstring of given length. */
 char *str_find (const str_t *str, const char *find); /* find a substring in a str_t string as a pointer. */
 ssize_t str_pos (const str_t *str, const char *find); /* find the index of a substring in a str_t string. */
+bool str_is_blank (const str_t *str); /* check if a string only consists of whitespace characters. */
 
 #endif // CUTILS_STR_H_

lib/str.c

@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "common.h"
+#include "cstr.h"
 
 #define STR_MIN_ALLOC 64 /* minimum allocation size for string data */
 
@@ -243,3 +244,18 @@ str_pos (const str_t *str, const char *find)
         return pos - str->str;
     return -1;
 }
+
+/**
+ * check if a string only consists of whitespace characters. whitespaces
+ * include the following characters: ' ', '\n', '\r', '\t', '\v', '\f'.
+ *
+ * @param   str: the string to check
+ *
+ * @return  true if the string only consists of whitespace characters, or false
+ *          if other characters are present. false in case of error.
+ */
+inline bool
+str_is_blank (const str_t *str)
+{
+    return strisblank (str->str);
+}