streaming: move logic to read packed objects streams into backend

Move the logic to read packed object streams into the respective
subsystem.

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

1 files changed, 128 insertions, 0 deletions

diff --git a/packfile.c b/packfile.c
index b4bc40d895..ad56ce0b90 100644
--- a/packfile.c
+++ b/packfile.c
@@ -20,6 +20,7 @@
 #include "tree.h"
 #include "object-file.h"
 #include "odb.h"
+#include "streaming.h"
 #include "midx.h"
 #include "commit-graph.h"
 #include "pack-revindex.h"
@@ -2406,3 +2407,130 @@ void packfile_store_close(struct packfile_store *store)
 		close_pack(p);
 	}
 }
+
+struct odb_packed_read_stream {
+	struct odb_read_stream base;
+	struct packed_git *pack;
+	git_zstream z;
+	enum {
+		ODB_PACKED_READ_STREAM_UNINITIALIZED,
+		ODB_PACKED_READ_STREAM_INUSE,
+		ODB_PACKED_READ_STREAM_DONE,
+		ODB_PACKED_READ_STREAM_ERROR,
+	} z_state;
+	off_t pos;
+};
+
+static ssize_t read_istream_pack_non_delta(struct odb_read_stream *_st, char *buf,
+					   size_t sz)
+{
+	struct odb_packed_read_stream *st = (struct odb_packed_read_stream *)_st;
+	size_t total_read = 0;
+
+	switch (st->z_state) {
+	case ODB_PACKED_READ_STREAM_UNINITIALIZED:
+		memset(&st->z, 0, sizeof(st->z));
+		git_inflate_init(&st->z);
+		st->z_state = ODB_PACKED_READ_STREAM_INUSE;
+		break;
+	case ODB_PACKED_READ_STREAM_DONE:
+		return 0;
+	case ODB_PACKED_READ_STREAM_ERROR:
+		return -1;
+	case ODB_PACKED_READ_STREAM_INUSE:
+		break;
+	}
+
+	while (total_read < sz) {
+		int status;
+		struct pack_window *window = NULL;
+		unsigned char *mapped;
+
+		mapped = use_pack(st->pack, &window,
+				  st->pos, &st->z.avail_in);
+
+		st->z.next_out = (unsigned char *)buf + total_read;
+		st->z.avail_out = sz - total_read;
+		st->z.next_in = mapped;
+		status = git_inflate(&st->z, Z_FINISH);
+
+		st->pos += st->z.next_in - mapped;
+		total_read = st->z.next_out - (unsigned char *)buf;
+		unuse_pack(&window);
+
+		if (status == Z_STREAM_END) {
+			git_inflate_end(&st->z);
+			st->z_state = ODB_PACKED_READ_STREAM_DONE;
+			break;
+		}
+
+		/*
+		 * Unlike the loose object case, we do not have to worry here
+		 * about running out of input bytes and spinning infinitely. If
+		 * we get Z_BUF_ERROR due to too few input bytes, then we'll
+		 * replenish them in the next use_pack() call when we loop. If
+		 * we truly hit the end of the pack (i.e., because it's corrupt
+		 * or truncated), then use_pack() catches that and will die().
+		 */
+		if (status != Z_OK && status != Z_BUF_ERROR) {
+			git_inflate_end(&st->z);
+			st->z_state = ODB_PACKED_READ_STREAM_ERROR;
+			return -1;
+		}
+	}
+	return total_read;
+}
+
+static int close_istream_pack_non_delta(struct odb_read_stream *_st)
+{
+	struct odb_packed_read_stream *st = (struct odb_packed_read_stream *)_st;
+	if (st->z_state == ODB_PACKED_READ_STREAM_INUSE)
+		git_inflate_end(&st->z);
+	return 0;
+}
+
+int packfile_store_read_object_stream(struct odb_read_stream **out,
+				      struct packfile_store *store,
+				      const struct object_id *oid)
+{
+	struct odb_packed_read_stream *stream;
+	struct pack_window *window = NULL;
+	struct object_info oi = OBJECT_INFO_INIT;
+	enum object_type in_pack_type;
+	unsigned long size;
+
+	oi.sizep = &size;
+
+	if (packfile_store_read_object_info(store, oid, &oi, 0) ||
+	    oi.u.packed.is_delta ||
+	    repo_settings_get_big_file_threshold(store->odb->repo) >= size)
+		return -1;
+
+	in_pack_type = unpack_object_header(oi.u.packed.pack,
+					    &window,
+					    &oi.u.packed.offset,
+					    &size);
+	unuse_pack(&window);
+	switch (in_pack_type) {
+	default:
+		return -1; /* we do not do deltas for now */
+	case OBJ_COMMIT:
+	case OBJ_TREE:
+	case OBJ_BLOB:
+	case OBJ_TAG:
+		break;
+	}
+
+	CALLOC_ARRAY(stream, 1);
+	stream->base.close = close_istream_pack_non_delta;
+	stream->base.read = read_istream_pack_non_delta;
+	stream->base.type = in_pack_type;
+	stream->base.size = size;
+	stream->z_state = ODB_PACKED_READ_STREAM_UNINITIALIZED;
+	stream->pack = oi.u.packed.pack;
+	stream->pos = oi.u.packed.offset;
+
+	*out = &stream->base;
+
+	return 0;
+}