[PATCH] tests/acpi/bios-tables-test: do not write new blobs unless there are changes

[Ani Sinha <anisinha@redhat.com>]

When dumping table blobs using rebuild-expected-aml.sh, table blobs from all
test variants are dumped regardless of whether there are any actual changes to
the tables or not. This creates lot of new files for various test variants that
are not part of the git repository. This is because we do not check in all table
blobs for all test variants into the repository. Only those blobs for those
variants that are different from the generic test-variant agnostic blob are
checked in.

This change makes the test smarter by checking if at all there are any changes
in the tables from the checked-in gold master blobs. If there are no changes,
no new files are written for test variants. However, existing files continue
to be overwritten regardless of whether there are changes. Hence, new files
will be generated only when there are actual changes in the tables.
This would make analyzing changes to tables less confusing and there would
be no need to clean useless untracked files when there are no table changes.

CC: peter.maydell@linaro.org
Signed-off-by: Ani Sinha <anisinha@redhat.com>
---
 tests/qtest/bios-tables-test.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/tests/qtest/bios-tables-test.c b/tests/qtest/bios-tables-test.c
index 9f4bc15aab..743b509e93 100644
--- a/tests/qtest/bios-tables-test.c
+++ b/tests/qtest/bios-tables-test.c
@@ -109,6 +109,7 @@ static const char *iasl;
 #endif
 
 static int verbosity_level;
+static GArray *load_expected_aml(test_data *data);
 
 static bool compare_signature(const AcpiSdtTable *sdt, const char *signature)
 {
@@ -241,21 +242,32 @@ static void test_acpi_fadt_table(test_data *data)
 
 static void dump_aml_files(test_data *data, bool rebuild)
 {
-    AcpiSdtTable *sdt;
+    AcpiSdtTable *sdt, *exp_sdt;
     GError *error = NULL;
     gchar *aml_file = NULL;
+    test_data exp_data = {};
     gint fd;
     ssize_t ret;
     int i;
 
+    exp_data.tables = load_expected_aml(data);
     for (i = 0; i < data->tables->len; ++i) {
         const char *ext = data->variant ? data->variant : "";
         sdt = &g_array_index(data->tables, AcpiSdtTable, i);
+        exp_sdt = &g_array_index(exp_data.tables, AcpiSdtTable, i);
         g_assert(sdt->aml);
+        g_assert(exp_sdt->aml);
 
         if (rebuild) {
             aml_file = g_strdup_printf("%s/%s/%.4s%s", data_dir, data->machine,
                                        sdt->aml, ext);
+            if (!g_file_test(aml_file, G_FILE_TEST_EXISTS) &&
+                sdt->aml_len == exp_sdt->aml_len &&
+                !memcmp(sdt->aml, exp_sdt->aml, sdt->aml_len)) {
+                /* identical tables, no need to write new files */
+                g_free(aml_file);
+                continue;
+            }
             fd = g_open(aml_file, O_WRONLY|O_TRUNC|O_CREAT,
                         S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH);
             if (fd < 0) {
-- 
2.42.0