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/*

 * Copyright (c) 1990 The Regents of the University of California.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms are permitted

 * provided that the above copyright notice and this paragraph are

 * duplicated in all such forms and that any documentation,

 * advertising materials, and other materials related to such

 * distribution and use acknowledge that the software was developed

 * by the University of California, Berkeley.  The name of the

 * University may not be used to endorse or promote products derived

 * from this software without specific prior written permission.

 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

 */

/*

FUNCTION

<<setvbuf>>---specify file or stream buffering

INDEX

        setvbuf

ANSI_SYNOPSIS

        #include <stdio.h>

        int setvbuf(FILE *<[fp]>, char *<[buf]>,

                    int <[mode]>, size_t <[size]>);

TRAD_SYNOPSIS

        #include <stdio.h>

        int setvbuf(<[fp]>, <[buf]>, <[mode]>, <[size]>)

        FILE *<[fp]>;

        char *<[buf]>;

        int <[mode]>;

        size_t <[size]>;

DESCRIPTION

Use <<setvbuf>> to specify what kind of buffering you want for the

file or stream identified by <[fp]>, by using one of the following

values (from <<stdio.h>>) as the <[mode]> argument:

o+

o _IONBF

Do not use a buffer: send output directly to the host system for the

file or stream identified by <[fp]>.

o _IOFBF

Use full output buffering: output will be passed on to the host system

only when the buffer is full, or when an input operation intervenes.

o _IOLBF

Use line buffering: pass on output to the host system at every

newline, as well as when the buffer is full, or when an input

operation intervenes.

o-

Use the <[size]> argument to specify how large a buffer you wish.  You

can supply the buffer itself, if you wish, by passing a pointer to a

suitable area of memory as <[buf]>.  Otherwise, you may pass <<NULL>>

as the <[buf]> argument, and <<setvbuf>> will allocate the buffer.

WARNINGS

You may only use <<setvbuf>> before performing any file operation other

than opening the file.

If you supply a non-null <[buf]>, you must ensure that the associated

storage continues to be available until you close the stream

identified by <[fp]>.

RETURNS

A <<0>> result indicates success, <<EOF>> failure (invalid <[mode]> or

<[size]> can cause failure).

PORTABILITY

Both ANSI C and the System V Interface Definition (Issue 2) require

<<setvbuf>>. However, they differ on the meaning of a <<NULL>> buffer

pointer: the SVID issue 2 specification says that a <<NULL>> buffer

pointer requests unbuffered output.  For maximum portability, avoid

<<NULL>> buffer pointers.

Both specifications describe the result on failure only as a

nonzero value.

Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,

<<lseek>>, <<read>>, <<sbrk>>, <<write>>.

*/

#include <_ansi.h>

#include <stdio.h>

#include <stdlib.h>

#include "local.h"

/*

 * Set one of the three kinds of buffering, optionally including a buffer.

 */

int

_DEFUN (setvbuf, (fp, buf, mode, size),

        register FILE * fp _AND

        char *buf _AND

        register int mode _AND

        register size_t size)

{

  int ret = 0;

  CHECK_INIT (fp);

  /*

   * Verify arguments.  The `int' limit on `size' is due to this

   * particular implementation.

   */

  if ((mode != _IOFBF && mode != _IOLBF && mode != _IONBF) || (int)(_POINTER_INT) size < 0)

    return (EOF);

  /*

   * 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.

   */

  (void) fflush (fp);

  fp->_r = 0;

  fp->_lbfsize = 0;

  if (fp->_flags & __SMBF)

    _free_r (fp->_data, (void *) fp->_bf._base);

  fp->_flags &= ~(__SLBF | __SNBF | __SMBF);

  if (mode == _IONBF)

    goto nbf;

  /*

   * Allocate buffer if needed. */

  if (buf == NULL)

    {

      /* we need this here because malloc() may return a pointer

         even if size == 0 */

      if (!size) size = BUFSIZ;

      if ((buf = malloc (size)) == NULL)

        {

          ret = EOF;

          /* Try another size... */

          buf = malloc (BUFSIZ);

          size = BUFSIZ;

        }

      if (buf == NULL)

        {

          /* Can't allocate it, let's try another approach */

nbf:

          fp->_flags |= __SNBF;

          fp->_w = 0;

          fp->_bf._base = fp->_p = fp->_nbuf;

          fp->_bf._size = 1;

          return (ret);

        }

      fp->_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.

   * If buf is NULL then make _lbfsize 0 to force the buffer

   * to be flushed and hence malloced on first use

   */

  switch (mode)

    {

    case _IOLBF:

      fp->_flags |= __SLBF;

      fp->_lbfsize = buf ? -size : 0;

      /* FALLTHROUGH */

    case _IOFBF:

      /* no flag */

      fp->_data->__cleanup = _cleanup_r;

      fp->_bf._base = fp->_p = (unsigned char *) buf;

      fp->_bf._size = size;

      break;

    }

  /*

   * Patch up write count if necessary.

   */

  if (fp->_flags & __SWR)

    fp->_w = fp->_flags & (__SLBF | __SNBF) ? 0 : size;

  return 0;

}