cmocka: Add all_zero() function and test

Reviewed-by: Joseph Sutton <jsutton@samba.org>

src/cmocka.c

@@ -1636,6 +1636,14 @@ static int string_not_equal_display_error(
     return 0;
 }
 
+static bool all_zero(const uint8_t *buf, size_t len)
+{
+    if (buf == NULL || len == 0) {
+        return true;
+    }
+
+    return buf[0] == '\0' && memcmp(buf, buf + 1, len - 1) == 0;
+}
 
 /*
  * Determine whether the specified areas of memory are equal.  If they're equal

tests/CMakeLists.txt

@@ -17,6 +17,7 @@ endif()
 
 set(CMOCKA_TESTS
     test_alloc
+    test_buffer
     test_expect_check
     test_expect_u_int_in_set
     test_expect_check_fail

tests/test_buffer.c

@@ -0,0 +1,48 @@
+#include "config.h"
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <setjmp.h>
+#include <stdint.h>
+#include <cmocka.h>
+#include <cmocka_private.h>
+
+#include "../src/cmocka.c"
+
+static const uint8_t buf0[] = {
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+};
+
+static const uint8_t buf1[] = {
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+};
+
+static void test_all_zero(void **state)
+{
+    (void)state;
+
+    assert_true(all_zero(buf0, sizeof(buf0)));
+
+    assert_true(all_zero(NULL, 0));
+
+    assert_true(all_zero(buf0, 0));
+
+    assert_false(all_zero(buf1, sizeof(buf1)));
+}
+
+int main(int argc, char **argv) {
+    const struct CMUnitTest buffer_tests[] = {
+        cmocka_unit_test(test_all_zero),
+    };
+
+    (void)argc;
+    (void)argv;
+
+    return cmocka_run_group_tests(buffer_tests, NULL, NULL);
+}