string: Add first_substring().

lib/misc/lvm-string.c

@@ -243,3 +243,19 @@ char *build_dm_uuid(struct dm_pool *mem, const struct logical_volume *lv,
 
 	return dlid;
 }
+
+char *first_substring(const char *str, ...)
+{
+	char *substr, *r = NULL;
+	va_list ap;
+
+	va_start(ap, str);
+
+	while ((substr = va_arg(ap, char *)))
+		if ((r = strstr(str, substr)))
+			break;
+
+	va_end(ap);
+
+	return r;
+}

lib/misc/lvm-string.h

@@ -49,4 +49,12 @@ void copy_systemid_chars(const char *src, char *dst);
 int apply_lvname_restrictions(const char *name);
 int is_reserved_lvname(const char *name);
 
+/*
+ * Provided with a NULL-terminated argument list of const char *
+ * substrings that might be contained within the string str, use
+ * strstr() to search str for each in turn and return a pointer to the
+ * first match or else NULL.
+ */
+char *first_substring(const char *str, ...);
+
 #endif