#ifndef lint
static char *RCSid = "$Header: /users/empire/EMP/client/RCS/ioqueue.c,v 1.3 89/06/09 23:37:49 jeffw Exp $";
#endif /* not lint */
/*
 * ioqueue.c
 *
 * Manage an i/o queue
 *
 */

#include <stdio.h>
#include <sys/types.h>
#include <sys/uio.h>
#include "queue.h"
#include "ioqueue.h"

ioq_init(ioq, bsize)
	struct	ioqueue *ioq;
{
	initque(&ioq->queue);
	ioq->cc = 0;
	ioq->bsize = bsize;
}

/*
 * copy batch of pointers into the passed
 * iovec, but don't actually dequeue the data.
 * return # of iovec initialized.
 */
int
ioq_peekiov(ioq, iov, max)
	struct	ioqueue *ioq;
	struct	iovec *iov;
	int	max;
{
	if (ioq->cc <= 0)
		return 0;
	return ioqtoiov(ioq, iov, max);
}

/*
 * Copy the specified number of characters into the buffer
 * provided, without actually dequeueing the data.  Return
 * number of bytes actually found.
 */
int
ioq_peek(ioq, buf, cc)
	struct	ioqueue *ioq;
	char	*buf;
	int	cc;
{
	return ioqtobuf(ioq, buf, cc);
}

int
ioq_dequeue(ioq, cc)
	struct	ioqueue *ioq;
	int	cc;
{
	if (dequeuecc(ioq, cc) != cc)
		return 0;
	return cc;
}

int
ioq_read(ioq, buf, cc)
	struct	ioqueue *ioq;
	char	*buf;
	int	cc;
{
	int	n;

	n = ioqtobuf(ioq, buf, cc);
	if (n > 0)
		dequeuecc(ioq, n);
	return n;
}

ioq_write(ioq, buf, cc)
	struct	ioqueue *ioq;
	char	*buf;
	int	cc;
{
	enqueuecc(ioq, buf, cc);
}

int
ioq_qsize(ioq)
	struct	ioqueue *ioq;
{
	return ioq->cc;
}

ioq_drain(ioq)
	struct	ioqueue *ioq;
{
	struct	io *io;
	struct	qelem *qp;

	while ((qp = ioq->queue.q_forw) != &ioq->queue) {
		io = (struct io *) qp;
		free(io->data);
		(void) remque(&io->queue);
		(void) free(io);
	}
	ioq->cc = 0;
}

char *
ioq_gets(ioq, buf, cc)
	struct	ioqueue *ioq;
	char	*buf;
	int	cc;
{
	register char *p;
	register char *end;
	int	nbytes;

	nbytes = ioqtobuf(ioq, buf, cc);
	if (nbytes < cc)
		cc = nbytes;
	end = &buf[cc];
	for (p = buf; p < end && *p; p++) {
		if (*p == '\n') {
			*p = '\0';
			dequeuecc(ioq, (p - buf) + 1);
			return buf;
		}
	}
	return 0;
}

/*
 * all the rest are local to this module
 */


/*
 * copy cc bytes from ioq to buf.
 * this routine doesn't free memory; this is
 * left for a higher level.
 */
static
int
ioqtobuf(ioq, buf, cc)
	register struct ioqueue *ioq;
	char	*buf;
	int	cc;
{
	register struct io *io;
	struct	qelem *qp;
	char	*offset;
	int	nbytes;
	int	nleft;

	nleft = cc;
	offset = buf;
	for (qp = ioq->queue.q_forw; qp != &ioq->queue; qp = qp->q_forw) {
		io = (struct io *) qp;
		if ((nbytes = io->nbytes - io->offset) < 0) {
			fprintf(stderr, "ioqtobuf: offset %d nbytes %d\n",
				io->offset, io->nbytes);
			continue;
		}
		if (nbytes > 0) {
			if (nleft < nbytes)
				nbytes = nleft;
			bcopy(io->data + io->offset, offset, nbytes);
			offset += nbytes;
			nleft -= nbytes;
		}
	}
	return offset - buf;
}

/*
 * translate "around" max bytes to an iovec
 * array.  The limit max is only advisory,
 * and more may get buffered.  It is an attempt to limit
 * really silly sends -- like sending 40k on a socket
 * with one writev for example.  This makes the processing
 * of a full ioqueue still be quick.
 */
static
int
ioqtoiov(ioq, iov, max)
	register struct ioqueue *ioq;
	register struct iovec *iov;
	register int max;
{
	register struct io *io;
	register int cc;
	register int niov;
	struct	qelem *qp;

	cc = 0;
	niov = 0;
	qp = ioq->queue.q_forw;
	for (qp = ioq->queue.q_forw; qp != &ioq->queue; qp = qp->q_forw) {
		io = (struct io *) qp;
		if (niov >= MAXIOV || cc >= max)
			break;
		iov->iov_base = io->data + io->offset;
		iov->iov_len = io->nbytes - io->offset;
		cc += io->nbytes - io->offset;
		niov++;
		iov++;
	}
	return niov;
}

/*
 * append a buffer to the end of the ioq.
 */
static
enqueuecc(ioq, buf, cc)
	struct	ioqueue *ioq;
	char	*buf;
	int	cc;
{
	struct	io *io;

	io = (struct io *) malloc(sizeof(*io));
	io->nbytes = cc;
	io->offset = 0;
	io->data = buf;
	insque(&io->queue, ioq->queue.q_back);
	ioq->cc += cc;
}

/*
 * remove cc bytes from ioqueue ioq
 * free memory, dequeue io elements
 * which are no longer used.
 */
static
int
dequeuecc(ioq, cc)
	register struct ioqueue *ioq;
	register int cc;
{
	register struct io *io;
	register struct qelem *qp;
	register int nbytes;
	register int there;

	nbytes = 0;
	while ((qp = ioq->queue.q_forw) != &ioq->queue) {
		io = (struct io *) qp;
		there = io->nbytes - io->offset;
		if (there < 0) {
			fprintf(stderr, "dequeuecc: nbytes %d, offset %d\n",
				io->nbytes, io->offset);
			continue;
		}
		if (cc > there) {
			cc -= there;
			nbytes += there;
			(void) remque(&io->queue);
			free(io->data);
		} else {
			io->offset += cc;
			nbytes += cc;
			break;
		}
	}
	ioq->cc -= nbytes;
	return nbytes;
}