/*
 * Copyright (c) 2000-2001 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: setvbuf.c,v 1.30 2001/02/28 20:25:18 rodney Exp $")
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <sm/io.h>
#include <sm/heap.h>
#include <sm/assert.h>
#include <sm/conf.h>
#include "local.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
**              timeout -- time allowed for completing the function
**              buf -- buffer to use
**              mode -- buffering method to use
**              size -- size of 'buf'
**
**      Returns:
**              Failure: SM_IO_EOF
**              Success: 0 (zero)
*/

int
sm_io_setvbuf(fp, timeout, buf, mode, size)
        SM_FILE_T *fp;
        int timeout;
        char *buf;
        int mode;
        size_t size;
{
        int ret, flags;
        size_t iosize;
        int ttyflag;
        int fd;
        struct timeval to;

        SM_REQUIRE_ISA(fp, SmFileMagic);

        /*
        **  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)
                if ((mode != SM_IO_FBF && mode != SM_IO_LBF &&
                    mode != SM_IO_NOW) || (int) size < 0)
                        return SM_IO_EOF;

        /*
        **  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.
        */

        ret = 0;
        SM_CONVERT_TIME(fp, fd, timeout, &to);
        (void) sm_flush(fp, &timeout);
        if (HASUB(fp))
                FREEUB(fp);
        fp->f_r = fp->f_lbfsize = 0;
        flags = fp->f_flags;
        if (flags & SMMBF)
        {
                sm_free((void *) fp->f_bf.smb_base);
                fp->f_bf.smb_base = NULL;
        }
        flags &= ~(SMLBF | SMNBF | SMMBF | SMOPT | SMNPT | SMFEOF | SMNOW |
                   SMFBF);

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

        /*
        **  Find optimal I/O size for seek optimization.  This also returns
        **  a `tty flag' to suggest that we check isatty(fd), but we do not
        **  care since our caller told us how to buffer.
        */

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

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

                        ret = SM_IO_EOF;
                        if (size != iosize)
                        {
                                size = iosize;
                                buf = sm_malloc(size);
                        }
                }
                if (buf == NULL)
                {
                        /* No luck; switch to unbuffered I/O. */
nbf:
                        fp->f_flags = flags | SMNBF;
                        fp->f_w = 0;
                        fp->f_bf.smb_base = fp->f_p = fp->f_nbuf;
                        fp->f_bf.smb_size = 1;
                        return ret;
                }
                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_LBF)
                flags |= SMLBF;
        else if (mode == SM_IO_NOW)
                flags |= SMNOW;
        else if (mode == SM_IO_FBF)
                flags |= SMFBF;
        fp->f_flags = flags;
        fp->f_bf.smb_base = fp->f_p = (unsigned char *)buf;
        fp->f_bf.smb_size = size;
        /* fp->f_lbfsize is still 0 */
        if (flags & SMWR)
        {
                /*
                **  Begin or continue writing: see sm_wsetup().  Note
                **  that SMNBF is impossible (it was handled earlier).
                */

                if (flags & SMLBF)
                {
                        fp->f_w = 0;
                        fp->f_lbfsize = -fp->f_bf.smb_size;
                }
                else
                        fp->f_w = size;
        }
        else
        {
                /* begin/continue reading, or stay in intermediate state */
                fp->f_w = 0;
        }

        atexit(sm_cleanup);
        return ret;
}