reftable/dump: support dumping a table's block structure

We're about to introduce new configs that will allow users to have more
control over how exactly reftables are written. To verify that these
configs are effective we will need to take a peak into the actual blocks
written by the reftable backend.

Introduce a new mode to the dumping logic that prints out the block
structure. This logic can be invoked via `test-tool dump-reftables -b`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/reftable/reader.c b/reftable/reader.c
index 481dff10d4..f23c8523db 100644
--- a/reftable/reader.c
+++ b/reftable/reader.c
@@ -856,3 +856,66 @@ done:
 	reftable_reader_free(r);
 	return err;
 }
+
+int reftable_reader_print_blocks(const char *tablename)
+{
+	struct {
+		const char *name;
+		int type;
+	} sections[] = {
+		{
+			.name = "ref",
+			.type = BLOCK_TYPE_REF,
+		},
+		{
+			.name = "obj",
+			.type = BLOCK_TYPE_OBJ,
+		},
+		{
+			.name = "log",
+			.type = BLOCK_TYPE_LOG,
+		},
+	};
+	struct reftable_block_source src = { 0 };
+	struct table_iter ti = TABLE_ITER_INIT;
+	struct reftable_reader *r = NULL;
+	size_t i;
+	int err;
+
+	err = reftable_block_source_from_file(&src, tablename);
+	if (err < 0)
+		goto done;
+
+	err = reftable_new_reader(&r, &src, tablename);
+	if (err < 0)
+		goto done;
+
+	printf("header:\n");
+	printf("  block_size: %d\n", r->block_size);
+
+	for (i = 0; i < ARRAY_SIZE(sections); i++) {
+		err = reader_start(r, &ti, sections[i].type, 0);
+		if (err < 0)
+			goto done;
+		if (err > 0)
+			continue;
+
+		printf("%s:\n", sections[i].name);
+
+		while (1) {
+			printf("  - length: %u\n", ti.br.block_len);
+			printf("    restarts: %u\n", ti.br.restart_count);
+
+			err = table_iter_next_block(&ti);
+			if (err < 0)
+				goto done;
+			if (err > 0)
+				break;
+		}
+	}
+
+done:
+	reftable_reader_free(r);
+	table_iter_close(&ti);
+	return err;
+}