The Bottom Layer Write Function
     int <write function>(qpstream, bufptr, sizeptr)
            QP_stream         *qpstream;
            unsigned char    **bufptr;
            size_t            *sizeptr;
     Return Values:   QP_SUCCESS

The bottom layer write function writes out a record from buffer address stored in *bufptr and the size of the record stored in *sizeptr. Upon successful return, *sizeptr stores the maximum record size and *bufptr stores the address of the beginning of the buffer for the next output record. The magic field in qpstream should be updated to the system-dependent file address (see fli-ios-sst-sda) for the beginning of the next output record. If there is no seek permission for the stream, the magic field may be ignored. The errno field in QP_stream stores the error code if an error is detected in the function and QP_ERROR is returned. The output record passed into the write function may be a partial record if output record overflows the output buffer for a stream that permits overflow.

     static int
     bin_write(qpstream, bufptr, sizeptr)
         QP_stream            *qpstream;
         unsigned char       **bufptr;
         size_t               *sizeptr;
             BinStream  *stream = CoerceBinStream(qpstream);
             int        n, len=(int) *sizeptr;
             char        *buf = (char *) *bufptr;
             while ((n = write(stream->fd, buf, len)) > 0 && n < len) {
                 buf += n;
                 len -= n;
             if (n >= 0) {
                 qpstream->magic.byteno += *sizeptr;
                 *sizeptr = qpstream->max_reclen;
                 *bufptr  = stream->buffer;
                 return QP_SUCCESS;
             } else {
                 qpstream->errno = errno;
                 return QP_ERROR;