void silc_sftp_write(SilcSFTP sftp,
                         SilcSFTPHandle handle,
                         SilcUInt64 offset,
                         const unsigned char *data,
                         SilcUInt32 data_len,
                         SilcSFTPStatusCallback callback,
                         void *context);

    Writes to a file indicated by the file handle `handle' starting from
    offset of `offset' at most `data_len' bytes of `data'.  The `callback'
    is called to indicate the status of the writing.