string-helpers.c: add str_starts_with()

t/meson.build

@@ -11,6 +11,7 @@ test_lib = static_library(
 
 tests = [
   'buf-simple',
+  'str',
 ]
 
 foreach t : tests

t/str.c

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define _POSIX_C_SOURCE 200809L
+#include <setjmp.h>
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#include <cmocka.h>
+#include "common/string-helpers.h"
+
+static void
+test_str_starts_with(void **state)
+{
+	(void)state;
+
+	assert_true(str_starts_with("  foo", 'f', " \t\r\n"));
+	assert_true(str_starts_with("f", 'f', " \t\r\n"));
+	assert_false(str_starts_with("  foo", '<', " "));
+}
+
+int main(int argc, char **argv)
+{
+	const struct CMUnitTest tests[] = {
+		cmocka_unit_test(test_str_starts_with),
+	};
+
+	return cmocka_run_group_tests(tests, NULL, NULL);
+}