reftable/table: move reading block into block reader

The logic to read blocks from a reftable is scattered across both the
table and the block subsystems. Besides causing somewhat fuzzy
responsibilities, it also means that we have to awkwardly pass around
the ownership of blocks between the subsystems.

Refactor the code so that we stop passing the block when initializing a
reader, but instead by passing in the block source plus the offset at
which we're supposed to read a block. Like this, the ownership of the
block itself doesn't need to get handed over as the block reader is the
one owning the block right from the start.

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

1 files changed, 6 insertions, 59 deletions

diff --git a/reftable/table.c b/reftable/table.c
index ec84545707..7c0f1c9e6e 100644
--- a/reftable/table.c
+++ b/reftable/table.c
@@ -30,23 +30,6 @@ table_offsets_for(struct reftable_table *t, uint8_t typ)
 	abort();
 }
 
-static int table_get_block(struct reftable_table *t,
-			   struct reftable_block *dest, uint64_t off,
-			   uint32_t sz)
-{
-	ssize_t bytes_read;
-	if (off >= t->size)
-		return 0;
-	if (off + sz > t->size)
-		sz = t->size - off;
-
-	bytes_read = block_source_read_block(&t->source, dest, off, sz);
-	if (bytes_read < 0)
-		return (int)bytes_read;
-
-	return 0;
-}
-
 enum reftable_hash reftable_table_hash_id(struct reftable_table *t)
 {
 	return t->hash_id;
@@ -180,64 +163,28 @@ static void table_iter_block_done(struct table_iter *ti)
 	block_iter_reset(&ti->bi);
 }
 
-static int32_t extract_block_size(uint8_t *data, uint8_t *typ, uint64_t off,
-				  int version)
-{
-	int32_t result = 0;
-
-	if (off == 0) {
-		data += header_size(version);
-	}
-
-	*typ = data[0];
-	if (reftable_is_block_type(*typ)) {
-		result = reftable_get_be24(data + 1);
-	}
-	return result;
-}
-
 int table_init_block_reader(struct reftable_table *t, struct block_reader *br,
 			    uint64_t next_off, uint8_t want_typ)
 {
-	int32_t guess_block_size = t->block_size ? t->block_size :
-							 DEFAULT_BLOCK_SIZE;
-	struct reftable_block block = { NULL };
-	uint8_t block_typ = 0;
-	int err = 0;
 	uint32_t header_off = next_off ? 0 : header_size(t->version);
-	int32_t block_size = 0;
+	int err;
 
 	if (next_off >= t->size)
 		return 1;
 
-	err = table_get_block(t, &block, next_off, guess_block_size);
+	err = block_reader_init(br, &t->source, next_off, header_off,
+				t->block_size, hash_size(t->hash_id));
 	if (err < 0)
 		goto done;
 
-	block_size = extract_block_size(block.data, &block_typ, next_off,
-					t->version);
-	if (block_size < 0) {
-		err = block_size;
-		goto done;
-	}
-	if (want_typ != BLOCK_TYPE_ANY && block_typ != want_typ) {
+	if (want_typ != BLOCK_TYPE_ANY && br->block_type != want_typ) {
 		err = 1;
 		goto done;
 	}
 
-	if (block_size > guess_block_size) {
-		block_source_return_block(&block);
-		err = table_get_block(t, &block, next_off, block_size);
-		if (err < 0) {
-			goto done;
-		}
-	}
-
-	err = block_reader_init(br, &block, header_off, t->block_size,
-				hash_size(t->hash_id));
 done:
-	block_source_return_block(&block);
-
+	if (err)
+		block_reader_release(br);
 	return err;
 }