+int check_pack_crc(struct packed_git *p, struct pack_window **w_curs,
+ off_t offset, off_t len, unsigned int nr)
+{
+ const uint32_t *index_crc;
+ uint32_t data_crc = crc32(0, Z_NULL, 0);
+
+ do {
+ unsigned int avail;
+ void *data = use_pack(p, w_curs, offset, &avail);
+ if (avail > len)
+ avail = len;
+ data_crc = crc32(data_crc, data, avail);
+ offset += avail;
+ len -= avail;
+ } while (len);
+
+ index_crc = p->index_data;
+ index_crc += 2 + 256 + p->num_objects * (20/4) + nr;
+
+ return data_crc != ntohl(*index_crc);
+}
+