t-reftable-block: add tests for index blocks

In the current testing setup, block operations are left unexercised
for index blocks. Add a test that exercises these operations for
index blocks.

Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Chandra Pratap <chandrapratap3519@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Chandra Pratap

t/unit-tests/t-reftable-block.c

@@ -272,8 +272,96 @@ static void t_obj_block_read_write(void)
 		reftable_record_release(&recs[i]);
 }
 
+static void t_index_block_read_write(void)
+{
+	const int header_off = 21;
+	struct reftable_record recs[30];
+	const size_t N = ARRAY_SIZE(recs);
+	const size_t block_size = 1024;
+	struct reftable_block block = { 0 };
+	struct block_writer bw = {
+		.last_key = STRBUF_INIT,
+	};
+	struct reftable_record rec = {
+		.type = BLOCK_TYPE_INDEX,
+		.u.idx.last_key = STRBUF_INIT,
+	};
+	size_t i = 0;
+	int ret;
+	struct block_reader br = { 0 };
+	struct block_iter it = BLOCK_ITER_INIT;
+	struct strbuf want = STRBUF_INIT, buf = STRBUF_INIT;
+
+	REFTABLE_CALLOC_ARRAY(block.data, block_size);
+	block.len = block_size;
+	block_source_from_strbuf(&block.source, &buf);
+	block_writer_init(&bw, BLOCK_TYPE_INDEX, block.data, block_size,
+			  header_off, hash_size(GIT_SHA1_FORMAT_ID));
+
+	for (i = 0; i < N; i++) {
+		strbuf_init(&recs[i].u.idx.last_key, 9);
+
+		recs[i].type = BLOCK_TYPE_INDEX;
+		strbuf_addf(&recs[i].u.idx.last_key, "branch%02"PRIuMAX, (uintmax_t)i);
+		recs[i].u.idx.offset = i;
+
+		ret = block_writer_add(&bw, &recs[i]);
+		check_int(ret, ==, 0);
+	}
+
+	ret = block_writer_finish(&bw);
+	check_int(ret, >, 0);
+
+	block_writer_release(&bw);
+
+	block_reader_init(&br, &block, header_off, block_size, GIT_SHA1_RAWSZ);
+
+	block_iter_seek_start(&it, &br);
+
+	for (i = 0; ; i++) {
+		ret = block_iter_next(&it, &rec);
+		check_int(ret, >=, 0);
+		if (ret > 0) {
+			check_int(i, ==, N);
+			break;
+		}
+		check(reftable_record_equal(&recs[i], &rec, GIT_SHA1_RAWSZ));
+	}
+
+	for (i = 0; i < N; i++) {
+		block_iter_reset(&it);
+		reftable_record_key(&recs[i], &want);
+
+		ret = block_iter_seek_key(&it, &br, &want);
+		check_int(ret, ==, 0);
+
+		ret = block_iter_next(&it, &rec);
+		check_int(ret, ==, 0);
+
+		check(reftable_record_equal(&recs[i], &rec, GIT_SHA1_RAWSZ));
+
+		want.len--;
+		ret = block_iter_seek_key(&it, &br, &want);
+		check_int(ret, ==, 0);
+
+		ret = block_iter_next(&it, &rec);
+		check_int(ret, ==, 0);
+		check(reftable_record_equal(&recs[10 * (i / 10)], &rec, GIT_SHA1_RAWSZ));
+	}
+
+	block_reader_release(&br);
+	block_iter_close(&it);
+	reftable_record_release(&rec);
+	reftable_block_done(&br.block);
+	strbuf_release(&want);
+	strbuf_release(&buf);
+	for (i = 0; i < N; i++)
+		reftable_record_release(&recs[i]);
+}
+
 int cmd_main(int argc, const char *argv[])
 {
+	TEST(t_index_block_read_write(), "read-write operations on index blocks work");
 	TEST(t_log_block_read_write(), "read-write operations on log blocks work");
 	TEST(t_obj_block_read_write(), "read-write operations on obj blocks work");
 	TEST(t_ref_block_read_write(), "read-write operations on ref blocks work");