/* Call function. The function is expected to */
/* call "FILTER_READ(idx+1, buf_sv)" first. */
/* Return: <0:error, =0:eof, >0:not eof */
/* Call function. The function is expected to */
/* call "FILTER_READ(idx+1, buf_sv)" first. */
/* Return: <0:error, =0:eof, >0:not eof */