/*
 * Copyright (c) 2000-2002 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/gen.h>
SM_RCSID("@(#)$Id: wsetup.c,v 1.20 2002/02/07 18:02:45 ca Exp $")
#include <stdlib.h>
#include <errno.h>
#include <sm/io.h>
#include "local.h"

/*
**  SM_WSETUP -- check writing is safe
**
**  Various output routines call wsetup to be sure it is safe to write,
**  because either flags does not include SMMWR, or buf is NULL.
**  Used in the macro "cantwrite" found in "local.h".
**
**      Parameters:
**              fp -- the file pointer
**
**      Results:
**              Failure: SM_IO_EOF and sets errno
**              Success: 0 (zero)
*/

int
sm_wsetup(fp)
        register SM_FILE_T *fp;
{
        /* make sure stdio is set up */
        if (!Sm_IO_DidInit)
                sm_init();

        /* If we are not writing, we had better be reading and writing. */
        if ((fp->f_flags & SMWR) == 0)
        {
                if ((fp->f_flags & SMRW) == 0)
                {
                        errno = EBADF;
                        return SM_IO_EOF;
                }
                if (fp->f_flags & SMRD)
                {
                        /* clobber any ungetc data */
                        if (HASUB(fp))
                                FREEUB(fp);

                        /* discard read buffer */
                        fp->f_flags &= ~(SMRD|SMFEOF);
                        fp->f_r = 0;
                        fp->f_p = fp->f_bf.smb_base;
                }
                fp->f_flags |= SMWR;
        }

        /* Make a buffer if necessary, then set w. */
        if (fp->f_bf.smb_base == NULL)
                sm_makebuf(fp);
        if (fp->f_flags & SMLBF)
        {
                /*
                **  It is line buffered, so make lbfsize be -bufsize
                **  for the sm_putc() macro.  We will change lbfsize back
                **  to 0 whenever we turn off SMWR.
                */

                fp->f_w = 0;
                fp->f_lbfsize = -fp->f_bf.smb_size;
        }
        else
                fp->f_w = fp->f_flags & SMNBF ? 0 : fp->f_bf.smb_size;
        return 0;
}