/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * %sccs.include.redist.c%
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)setvbuf.c	5.4 (Berkeley) 12/04/92";
#endif /* LIBC_SCCS and not lint */

#include <stdio.h>
#include <stdlib.h>
#include "local.h"

/*
 * Set one of the three kinds of buffering, optionally including
 * a buffer.
 */
setvbuf(fp, buf, mode, size)
	register FILE *fp;
	char *buf;
	register int mode;
	register size_t size;
{
	register int ret, flags;

	/*
	 * Verify arguments.  The `int' limit on `size' is due to this
	 * particular implementation.
	 */
	if ((mode != _IOFBF && mode != _IOLBF && mode != _IONBF) ||
	    (int)size < 0)
		return (EOF);

	/*
	 * OK so far.  Write current buffer, if any; drop read count, if
	 * any.  Make sure putc() will not think fp is line buffered.  Free
	 * old buffer if it was from malloc().  Clear line and non-buffer
	 * flags, and clear malloc flag.
	 */
	ret = 0;
	(void) __sflush(fp);
	fp->_r = 0;
	fp->_lbfsize = 0;
	flags = fp->_flags;
	if (flags & __SMBF)
		free((void *)fp->_bf._base);
	flags &= ~(__SLBF | __SNBF | __SMBF);

	if (size == 0)
		buf = NULL;	/* we will make a real one later */
	else if (buf == NULL) {
		/*
		 * Caller wants specific buffering mode and size but did
		 * not provide a buffer.  Produce one of the given size.
		 * If that fails, set the size to 0 and continue, so that
		 * we will try again later with a system-supplied size
		 * (failure here is probably from someone with the bogus
		 * idea that larger is always better, asking for many MB),
		 * but return EOF to indicate failure.
		 */
		if ((buf = malloc(size)) == NULL) {
			ret = EOF;
			size = 0;
		} else
			flags |= __SMBF;
	}

	/*
	 * Now put back whichever flag is needed, and fix _lbfsize if line
	 * buffered.  Ensure output flush on exit if the stream will be
	 * buffered at all.
	 */
	switch (mode) {

	case _IONBF:
		flags |= __SNBF;
		fp->_bf._base = fp->_p = fp->_nbuf;
		fp->_bf._size = 1;
		break;

	case _IOLBF:
		flags |= __SLBF;
		fp->_lbfsize = -size;
		/* FALLTHROUGH */

	case _IOFBF:
		/* no flag */
		__cleanup = _cleanup;
		fp->_bf._base = fp->_p = (unsigned char *)buf;
		fp->_bf._size = size;
		break;
	}

	/*
	 * Patch up write count if necessary.
	 */
	if (flags & __SWR)
		fp->_w = flags & (__SLBF | __SNBF) ? 0 : size;
	fp->_flags = flags;

	return (ret);
}