+extern int unpack_sha1_header(z_stream *stream, void *map, unsigned long mapsize, void *buffer, unsigned long size);
+extern int parse_sha1_header(char *hdr, char *type, unsigned long *sizep);
+extern int sha1_delta_base(const unsigned char *, unsigned char *);
+extern int sha1_file_size(const unsigned char *, unsigned long *);