pack: move get_size_from_delta()

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/packfile.c b/packfile.c
index 1116942043..9e0bbf5a0e 100644
--- a/packfile.c
+++ b/packfile.c
@@ -4,6 +4,7 @@
 #include "dir.h"
 #include "mergesort.h"
 #include "packfile.h"
+#include "delta.h"
 
 char *odb_pack_name(struct strbuf *buf,
 		    const unsigned char *sha1,
@@ -909,3 +910,42 @@ unsigned long unpack_object_header_buffer(const unsigned char *buf,
 	*sizep = size;
 	return used;
 }
+
+unsigned long get_size_from_delta(struct packed_git *p,
+				  struct pack_window **w_curs,
+				  off_t curpos)
+{
+	const unsigned char *data;
+	unsigned char delta_head[20], *in;
+	git_zstream stream;
+	int st;
+
+	memset(&stream, 0, sizeof(stream));
+	stream.next_out = delta_head;
+	stream.avail_out = sizeof(delta_head);
+
+	git_inflate_init(&stream);
+	do {
+		in = use_pack(p, w_curs, curpos, &stream.avail_in);
+		stream.next_in = in;
+		st = git_inflate(&stream, Z_FINISH);
+		curpos += stream.next_in - in;
+	} while ((st == Z_OK || st == Z_BUF_ERROR) &&
+		 stream.total_out < sizeof(delta_head));
+	git_inflate_end(&stream);
+	if ((st != Z_STREAM_END) && stream.total_out != sizeof(delta_head)) {
+		error("delta data unpack-initial failed");
+		return 0;
+	}
+
+	/* Examine the initial part of the delta to figure out
+	 * the result size.
+	 */
+	data = delta_head;
+
+	/* ignore base size */
+	get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
+
+	/* Read the result size */
+	return get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
+}