streaming: move zlib stream into backends

While all backend-specific data is now contained in a backend-specific
structure, we still share the zlib stream across the loose and packed
objects.

Refactor the code and move it into the specific structures so that we
fully detangle the different backends from one another.

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

Author: pks-t

streaming.c

@@ -25,23 +25,8 @@ struct odb_read_stream {
 
 	enum object_type type;
 	unsigned long size; /* inflated size of full object */
-	git_zstream z;
-	enum { z_unused, z_used, z_done, z_error } z_state;
 };
 
-/*****************************************************************
- *
- * Common helpers
- *
- *****************************************************************/
-
-static void close_deflated_stream(struct odb_read_stream *st)
-{
-	if (st->z_state == z_used)
-		git_inflate_end(&st->z);
-}
-
-
 /*****************************************************************
  *
  * Filtered stream
@@ -150,6 +135,12 @@ static struct odb_read_stream *attach_stream_filter(struct odb_read_stream *st,
 
 struct odb_loose_read_stream {
 	struct odb_read_stream base;
+	git_zstream z;
+	enum {
+		ODB_LOOSE_READ_STREAM_INUSE,
+		ODB_LOOSE_READ_STREAM_DONE,
+		ODB_LOOSE_READ_STREAM_ERROR,
+	} z_state;
 	void *mapped;
 	unsigned long mapsize;
 	char hdr[32];
@@ -162,10 +153,10 @@ static ssize_t read_istream_loose(struct odb_read_stream *_st, char *buf, size_t
 	struct odb_loose_read_stream *st = (struct odb_loose_read_stream *)_st;
 	size_t total_read = 0;
 
-	switch (st->base.z_state) {
-	case z_done:
+	switch (st->z_state) {
+	case ODB_LOOSE_READ_STREAM_DONE:
 		return 0;
-	case z_error:
+	case ODB_LOOSE_READ_STREAM_ERROR:
 		return -1;
 	default:
 		break;
@@ -183,20 +174,20 @@ static ssize_t read_istream_loose(struct odb_read_stream *_st, char *buf, size_t
 	while (total_read < sz) {
 		int status;
 
-		st->base.z.next_out = (unsigned char *)buf + total_read;
-		st->base.z.avail_out = sz - total_read;
-		status = git_inflate(&st->base.z, Z_FINISH);
+		st->z.next_out = (unsigned char *)buf + total_read;
+		st->z.avail_out = sz - total_read;
+		status = git_inflate(&st->z, Z_FINISH);
 
-		total_read = st->base.z.next_out - (unsigned char *)buf;
+		total_read = st->z.next_out - (unsigned char *)buf;
 
 		if (status == Z_STREAM_END) {
-			git_inflate_end(&st->base.z);
-			st->base.z_state = z_done;
+			git_inflate_end(&st->z);
+			st->z_state = ODB_LOOSE_READ_STREAM_DONE;
 			break;
 		}
 		if (status != Z_OK && (status != Z_BUF_ERROR || total_read < sz)) {
-			git_inflate_end(&st->base.z);
-			st->base.z_state = z_error;
+			git_inflate_end(&st->z);
+			st->z_state = ODB_LOOSE_READ_STREAM_ERROR;
 			return -1;
 		}
 	}
@@ -206,7 +197,8 @@ static ssize_t read_istream_loose(struct odb_read_stream *_st, char *buf, size_t
 static int close_istream_loose(struct odb_read_stream *_st)
 {
 	struct odb_loose_read_stream *st = (struct odb_loose_read_stream *)_st;
-	close_deflated_stream(&st->base);
+	if (st->z_state == ODB_LOOSE_READ_STREAM_INUSE)
+		git_inflate_end(&st->z);
 	munmap(st->mapped, st->mapsize);
 	return 0;
 }
@@ -238,7 +230,7 @@ static int open_istream_loose(struct odb_read_stream **out,
 	 */
 	CALLOC_ARRAY(st, 1);
 
-	switch (unpack_loose_header(&st->base.z, mapped, mapsize, st->hdr,
+	switch (unpack_loose_header(&st->z, mapped, mapsize, st->hdr,
 				    sizeof(st->hdr))) {
 	case ULHR_OK:
 		break;
@@ -256,16 +248,16 @@ static int open_istream_loose(struct odb_read_stream **out,
 	st->mapped = mapped;
 	st->mapsize = mapsize;
 	st->hdr_used = strlen(st->hdr) + 1;
-	st->hdr_avail = st->base.z.total_out;
-	st->base.z_state = z_used;
+	st->hdr_avail = st->z.total_out;
+	st->z_state = ODB_LOOSE_READ_STREAM_INUSE;
 	st->base.close = close_istream_loose;
 	st->base.read = read_istream_loose;
 
 	*out = &st->base;
 
 	return 0;
 error:
-	git_inflate_end(&st->base.z);
+	git_inflate_end(&st->z);
 	munmap(st->mapped, st->mapsize);
 	free(st);
 	return -1;
@@ -281,6 +273,13 @@ static int open_istream_loose(struct odb_read_stream **out,
 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;
 };
 
@@ -290,17 +289,17 @@ static ssize_t read_istream_pack_non_delta(struct odb_read_stream *_st, char *bu
 	struct odb_packed_read_stream *st = (struct odb_packed_read_stream *)_st;
 	size_t total_read = 0;
 
-	switch (st->base.z_state) {
-	case z_unused:
-		memset(&st->base.z, 0, sizeof(st->base.z));
-		git_inflate_init(&st->base.z);
-		st->base.z_state = z_used;
+	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 z_done:
+	case ODB_PACKED_READ_STREAM_DONE:
 		return 0;
-	case z_error:
+	case ODB_PACKED_READ_STREAM_ERROR:
 		return -1;
-	case z_used:
+	case ODB_PACKED_READ_STREAM_INUSE:
 		break;
 	}
 
@@ -310,20 +309,20 @@ static ssize_t read_istream_pack_non_delta(struct odb_read_stream *_st, char *bu
 		unsigned char *mapped;
 
 		mapped = use_pack(st->pack, &window,
-				  st->pos, &st->base.z.avail_in);
+				  st->pos, &st->z.avail_in);
 
-		st->base.z.next_out = (unsigned char *)buf + total_read;
-		st->base.z.avail_out = sz - total_read;
-		st->base.z.next_in = mapped;
-		status = git_inflate(&st->base.z, Z_FINISH);
+		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->base.z.next_in - mapped;
-		total_read = st->base.z.next_out - (unsigned char *)buf;
+		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->base.z);
-			st->base.z_state = z_done;
+			git_inflate_end(&st->z);
+			st->z_state = ODB_PACKED_READ_STREAM_DONE;
 			break;
 		}
 
@@ -336,8 +335,8 @@ static ssize_t read_istream_pack_non_delta(struct odb_read_stream *_st, char *bu
 		 * or truncated), then use_pack() catches that and will die().
 		 */
 		if (status != Z_OK && status != Z_BUF_ERROR) {
-			git_inflate_end(&st->base.z);
-			st->base.z_state = z_error;
+			git_inflate_end(&st->z);
+			st->z_state = ODB_PACKED_READ_STREAM_ERROR;
 			return -1;
 		}
 	}
@@ -347,7 +346,8 @@ static ssize_t read_istream_pack_non_delta(struct odb_read_stream *_st, char *bu
 static int close_istream_pack_non_delta(struct odb_read_stream *_st)
 {
 	struct odb_packed_read_stream *st = (struct odb_packed_read_stream *)_st;
-	close_deflated_stream(&st->base);
+	if (st->z_state == ODB_PACKED_READ_STREAM_INUSE)
+		git_inflate_end(&st->z);
 	return 0;
 }
 
@@ -384,7 +384,7 @@ static int open_istream_pack_non_delta(struct odb_read_stream **out,
 	stream->base.read = read_istream_pack_non_delta;
 	stream->base.type = in_pack_type;
 	stream->base.size = size;
-	stream->base.z_state = z_unused;
+	stream->z_state = ODB_PACKED_READ_STREAM_UNINITIALIZED;
 	stream->pack = pack;
 	stream->pos = offset;