substdi.c

/*
 * $Log: substdi.c,v $
 * Revision 1.1  2014-08-23 09:07:05+05:30  Cprogrammer
 * Initial revision
 *
 *
 */
#include "substdio.h"
#include "byte.h"
#include "error.h"

#ifndef	lint
static char     sccsid[] = "$Id: substdi.c,v 1.1 2014-08-23 09:07:05+05:30 Cprogrammer Exp mbhangui $";
#endif

static int
oneread(op, fd, buf, len)
	register ssize_t (*op) ();
	register int    fd;
	register char  *buf;
	register int    len;
{
	register int    r;

	for (;;)
	{
		r = op(fd, buf, len);
		if (r == -1)
			if (errno == error_intr)
				continue;
		return r;
	}
}

static int
getthis(s, buf, len)
	register substdio *s;
	register char  *buf;
	register int    len;
{
	register int    r;
	register int    q;

	r = s->p;
	q = r - len;
	if (q > 0)
	{
		r = len;
		s->p = q;
	} else
		s->p = 0;
	byte_copy(buf, r, s->x + s->n);
	s->n += r;
	return r;
}

int
substdio_feed(s)
	register substdio *s;
{
	register int    r;
	register int    q;

	if (s->p)
		return s->p;
	q = s->n;
	r = oneread(s->op, s->fd, s->x, q);
	if (r <= 0)
		return r;
	s->p = r;
	q -= r;
	s->n = q;
	if (q > 0)	/*- damn, gotta shift */
		byte_copyr(s->x + q, r, s->x);
	return r;
}

int
substdio_bget(s, buf, len)
	register substdio *s;
	register char  *buf;
	register int    len;
{
	register int    r;

	if (s->p > 0)
		return getthis(s, buf, len);
	r = s->n;
	if (r <= len)
		return oneread(s->op, s->fd, buf, r);
	r = substdio_feed(s);
	if (r <= 0)
		return r;
	return getthis(s, buf, len);
}

int
substdio_get(s, buf, len)
	register substdio *s;
	register char  *buf;
	register int    len;
{
	register int    r;

	if (s->p > 0)
		return getthis(s, buf, len);
	if (s->n <= len)
		return oneread(s->op, s->fd, buf, len);
	r = substdio_feed(s);
	if (r <= 0)
		return r;
	return getthis(s, buf, len);
}

char           *
substdio_peek(s)
	register substdio *s;
{
	return s->x + s->n;
}

void
substdio_seek(s, len)
	register substdio *s;
	register int    len;
{
	s->n += len;
	s->p -= len;
}