string-helpers.c: add str_starts_with()

include/common/string-helpers.h

@@ -73,4 +73,12 @@ char *str_join(const char *const parts[],
  */
 bool str_endswith(const char *const string, const char *const suffix);
 
+/**
+ * str_starts_with - indicate whether a string starts with a given character
+ * @string: string to test
+ * @needle: character to expect in string
+ * @ignore_chars: characters to ignore at start such as space and "\t"
+ */
+bool str_starts_with(const char *s, char needle, const char *ignore_chars);
+
 #endif /* LABWC_STRING_HELPERS_H */

src/common/string-helpers.c

@@ -170,3 +170,10 @@ str_endswith(const char *const string, const char *const suffix)
 
 	return strcmp(string + len_str - len_sfx, suffix) == 0;
 }
+
+bool
+str_starts_with(const char *s, char needle, const char *ignore_chars)
+{
+	return (s + strspn(s, ignore_chars))[0] == needle;
+}
+

src/menu/menu.c

@@ -1419,12 +1419,6 @@ handle_pipemenu_timeout(void *_ctx)
 	return 0;
 }
 
-static bool
-starts_with_less_than(const char *s)
-{
-	return (s + strspn(s, " \t\r\n"))[0] == '<';
-}
-
 static int
 handle_pipemenu_readable(int fd, uint32_t mask, void *_ctx)
 {
@@ -1468,7 +1462,7 @@ handle_pipemenu_readable(int fd, uint32_t mask, void *_ctx)
 	}
 
 	/* Guard against badly formed data such as binary input */
-	if (!starts_with_less_than(ctx->buf.data)) {
+	if (!str_starts_with(ctx->buf.data, '<', " \t\r\n")) {
 		wlr_log(WLR_ERROR, "expect xml data to start with '<'; abort pipemenu");
 		goto clean_up;
 	}

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);
+}