/*
 * Copyright (c) 2000-2002, 2005 Sendmail, Inc. and its suppliers.
 *      All rights reserved.
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * By using this file, you agree to the terms and conditions set
 * forth in the LICENSE file which can be found at the top level of
 * the sendmail distribution.
 */

#include "sm/generic.h"
SM_RCSID("@(#)$Id: setvbuf.c,v 1.10 2006/07/14 14:42:25 ca Exp $")
#include "sm/assert.h"
#include "sm/error.h"
#include "sm/io.h"
#include "sm/fcntl.h"
#include "sm/heap.h"
#include "io-int.h"

/*
**  SM_IO_SETVBUF -- set the buffering type for a file
**
**  Set one of the different kinds of buffering, optionally including
**  a buffer.
**  If 'size' is == 0 then an "optimal" size will be selected.
**  If 'buf' is == NULL then space will be allocated at 'size'.
**
**	Parameters:
**		fp -- the file that buffering is to be changed for
**		buf -- buffer to use
**		mode -- buffering method to use
**		size -- size of 'buf'
**
**	Returns:
**		usual sm_error
*/

sm_ret_T
sm_io_setvbuf(sm_file_T *fp, uchar *buf, int mode, size_t size)
{
	sm_f_flags_T flags;
	size_t iosize;
	sm_ret_T res;

	SM_IS_FP(fp);

	/*
	**  Verify arguments.  The `int' limit on `size' is due to this
	**  particular implementation.  Note, buf and size are ignored
	**  when setting SM_IO_NBF.
	*/

	if (mode != SM_IO_NBF && (mode != SM_IO_FBF || (int) size < 0))
		return sm_error_perm(SM_EM_IO, EINVAL);

	/*
	**  Write current buffer, if any.  Discard unread input (including
	**  ungetc data), cancel line buffering, and free old buffer if
	**  malloc()ed.  We also clear any eof condition, as if this were
	**  a seek.
	*/

	res = 0;
	(void) sm_flush(fp);
	f_r(*fp) = 0;
	flags = f_flags(*fp);
	if (flags & SMMBF)
	{
		sm_free((void *) f_bfbase(*fp));
		f_bfbase(*fp) = NULL;
	}
	flags &= ~(SMNBF | SMMBF | SMOPT | SMNPT | SMFEOF | SMFBF);

	/* If setting unbuffered mode, skip all the hard work. */
	if (mode == SM_IO_NBF)
		goto nbf;

	flags |= sm_whatbuf(fp, &iosize);
	if (size == 0)
	{
		buf = NULL;	/* force local allocation */
		size = iosize;
	}

	/* Allocate buffer if needed. */
	if (buf == NULL)
	{
		buf = (uchar *) sm_malloc(size);
		if (buf == NULL)
		{
			/*
			**  Unable to honor user's request.  We will return
			**  failure, but try again with file system size.
			*/

			res = sm_error_temp(SM_EM_IO, ENOMEM);
			if (size != iosize)
			{
				size = iosize;
				buf = (uchar *) sm_malloc(size);
			}
		}
		if (buf == NULL)
		{
			/* No luck; switch to unbuffered I/O. */
  nbf:
			f_flags(*fp) = flags | SMNBF;
			f_w(*fp) = 0;
			f_bfbase(*fp) = f_p(*fp) = fp->f_nbuf;
			f_bfsize(*fp) = 1;
			return res;
		}
		flags |= SMMBF;
	}

	/*
	**  Kill any seek optimization if the buffer is not the
	**  right size.
	**
	**  SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
	*/

	if (size != iosize)
		flags |= SMNPT;

	/*
	**  Fix up the sm_file_T fields, and set sm_cleanup for output flush on
	**  exit (since we are buffered in some way).
	*/

	if (mode == SM_IO_FBF)
		flags |= SMFBF;
	f_flags(*fp) = flags;
	f_bfbase(*fp) = f_p(*fp) = buf;
	f_bfsize(*fp) = size;
	if (flags & SMWR)
	{
		/*
		**  Begin or continue writing: see sm_wsetup().  Note
		**  that SMNBF is impossible (it was handled earlier).
		*/

		f_w(*fp) = size;
	}
	else
	{
		/* begin/continue reading, or stay in intermediate state */
		f_w(*fp) = 0;
	}

	return res;
}