4.3BSD/usr/ingres/source/libq/IIpb_get.c

# include	<useful.h>
# include	<pipes.h>
# include	<sccs.h>

SCCSID(@(#)IIpb_get.c	8.1	12/31/84)


/*
**  IIPB_GET -- buffered get from pipe
**
**	This routine just gets a record from the pipe block, reading
**	if necessary.  It tries to do things in big chunks to keep
**	the overhead down.
**
**	Parameters:
**		ppb -- a pointer to the pipe block to unbuffer.
**		dp -- a pointer to the data area.
**		len -- the number of bytes to read.
**
**	Returns:
**		The number of bytes actually read.
**		Zero on end of file.
**
**	Side Effects:
**		none.
**
**	Trace Flags:
**		18.1 - 18.7
*/

IIpb_get(ppb, dp, len)
register pb_t	*ppb;
char		*dp;
register int	len;
{
	int		rct;
	register int	i;

	rct = 0;

	/*
	**  Top Loop.
	**	As long as we still want more, keep buffering out.
	*/

	while (len > 0)
	{
		/* if we have no data, read another block */
		while (ppb->pb_nleft <= 0)
		{
			if (bitset(PB_EOF, ppb->pb_stat))
				return (rct);
			IIpb_read(ppb);
		}

		/*
		**  Compute the length to move.
		**	This is the min of the amount we want and the
		**	amount we have available to us in the buffer.
		*/

		i = min(ppb->pb_nleft, len);
		IIbmove(ppb->pb_xptr, dp, i);
		ppb->pb_xptr += i;
		ppb->pb_nleft -= i;
		dp += i;
		len -= i;
		rct += i;
	}

	return (rct);
}