может это вам поможет с наведением на мысль?
/* If d_compr is incorrect scanning will result in CL_EZIP (Zip
* module failure)
*/
if(!hdr->d_compr && hdr->d_csize != hdr->d_usize) {
cli_dbgmsg("Zziplib: File claims to be stored but csize != usize\n");
cli_dbgmsg("Zziplib: Switching to the inflate method\n");
hdr->d_compr = 8;
} else if(hdr->d_compr && hdr->d_csize == hdr->d_usize) {
cli_dbgmsg("Zziplib: File claims to be deflated but csize == usize\n");
cli_dbgmsg("Zziplib: Switching to the stored method\n");
hdr->d_compr = 0;
}