reftable: ensure that obj_id_len is >= 2 on writing

When writing the same hash many times, we might decide to use a
length-1 object ID prefix for the ObjectID => ref table, which is out
of spec.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/reftable/readwrite_test.c b/reftable/readwrite_test.c
index fd5922e55f61a4dbc79e0571c41a281d7db2efb1..35142eb070e7d275504f08bc14ad9a1a2e849809 100644 (file)
--- a/reftable/readwrite_test.c
+++ b/reftable/readwrite_test.c
@@ -667,6 +667,42 @@ static void test_write_empty_table(void)
        strbuf_release(&buf);
 }
 
+static void test_write_object_id_min_length(void)
+{
+       struct reftable_write_options opts = {
+               .block_size = 75,
+       };
+       struct strbuf buf = STRBUF_INIT;
+       struct reftable_writer *w =
+               reftable_new_writer(&strbuf_add_void, &buf, &opts);
+       uint8_t hash[GIT_SHA1_RAWSZ] = {42};
+       struct reftable_ref_record ref = {
+               .update_index = 1,
+               .value_type = REFTABLE_REF_VAL1,
+               .value.val1 = hash,
+       };
+       int err;
+       int i;
+
+       reftable_writer_set_limits(w, 1, 1);
+
+       /* Write the same hash in many refs. If there is only 1 hash, the
+        * disambiguating prefix is length 0 */
+       for (i = 0; i < 256; i++) {
+               char name[256];
+               snprintf(name, sizeof(name), "ref%05d", i);
+               ref.refname = name;
+               err = reftable_writer_add_ref(w, &ref);
+               EXPECT_ERR(err);
+       }
+
+       err = reftable_writer_close(w);
+       EXPECT_ERR(err);
+       EXPECT(writer_stats(w)->object_id_len == 2);
+       reftable_writer_free(w);
+       strbuf_release(&buf);
+}
+
 static void test_write_empty_key(void)
 {
        struct reftable_write_options opts = { 0 };
@@ -772,5 +808,6 @@ int readwrite_test_main(int argc, const char *argv[])
        RUN_TEST(test_write_empty_key);
        RUN_TEST(test_write_empty_table);
        RUN_TEST(test_log_overflow);
+       RUN_TEST(test_write_object_id_min_length);
        return 0;
 }

diff --git a/reftable/writer.c b/reftable/writer.c
index d54215a50dc2fec6168bf3e93478e5453f2be25f..5e4e6e9341606e36c2b352183efd363a222cda65 100644 (file)
--- a/reftable/writer.c
+++ b/reftable/writer.c
@@ -515,7 +515,9 @@ static void object_record_free(void *void_arg, void *key)
 static int writer_dump_object_index(struct reftable_writer *w)
 {
        struct write_record_arg closure = { .w = w };
-       struct common_prefix_arg common = { NULL };
+       struct common_prefix_arg common = {
+               .max = 1,               /* obj_id_len should be >= 2. */
+       };
        if (w->obj_index_tree) {
                infix_walk(w->obj_index_tree, &update_common, &common);
        }