pack: move check_pack_index_ptr(), nth_packed_object_offset()

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

1 files changed, 33 insertions, 0 deletions

diff --git a/packfile.c b/packfile.c
index cc8d0d7db..f251e3878 100644
--- a/packfile.c
+++ b/packfile.c
@@ -1667,3 +1667,36 @@ const struct object_id *nth_packed_object_oid(struct object_id *oid,
 	hashcpy(oid->hash, hash);
 	return oid;
 }
+
+void check_pack_index_ptr(const struct packed_git *p, const void *vptr)
+{
+	const unsigned char *ptr = vptr;
+	const unsigned char *start = p->index_data;
+	const unsigned char *end = start + p->index_size;
+	if (ptr < start)
+		die(_("offset before start of pack index for %s (corrupt index?)"),
+		    p->pack_name);
+	/* No need to check for underflow; .idx files must be at least 8 bytes */
+	if (ptr >= end - 8)
+		die(_("offset beyond end of pack index for %s (truncated index?)"),
+		    p->pack_name);
+}
+
+off_t nth_packed_object_offset(const struct packed_git *p, uint32_t n)
+{
+	const unsigned char *index = p->index_data;
+	index += 4 * 256;
+	if (p->index_version == 1) {
+		return ntohl(*((uint32_t *)(index + 24 * n)));
+	} else {
+		uint32_t off;
+		index += 8 + p->num_objects * (20 + 4);
+		off = ntohl(*((uint32_t *)(index + 4 * n)));
+		if (!(off & 0x80000000))
+			return off;
+		index += p->num_objects * 4 + (off & 0x7fffffff) * 8;
+		check_pack_index_ptr(p, index);
+		return (((uint64_t)ntohl(*((uint32_t *)(index + 0)))) << 32) |
+				   ntohl(*((uint32_t *)(index + 4)));
+	}
+}