glibc/stdio/setvbuf.c

/* Copyright (C) 1991, 1993, 1995, 1996, 1997 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>


/* Make STREAM use the buffering method given in MODE.
   If MODE indicates full or line buffering, use BUF,
   a buffer of SIZE bytes; if BUF is NULL, malloc a buffer.  */
int
setvbuf (stream, buf, mode, size)
     FILE *stream;
     char *buf;
     int mode;
     size_t size;
{
  if (!__validfp (stream))
    {
      __set_errno (EINVAL);
      return EOF;
    }

  /* The ANSI standard says setvbuf can only be called before any I/O is done,
     but we allow it to replace an old buffer, flushing it first.  */
  if (stream->__buffer != NULL)
    {
      (void) fflush (stream);
      /* Free the old buffer if it was malloc'd.  */
      if (!stream->__userbuf)
	free(stream->__buffer);
    }

  stream->__get_limit = stream->__put_limit = NULL;
  stream->__bufp = stream->__buffer = NULL;
  stream->__userbuf = stream->__linebuf = stream->__linebuf_active = 0;

  switch (mode)
    {
    default:
      __set_errno (EINVAL);
      return EOF;
    case _IONBF:	/* Unbuffered.  */
      stream->__buffer = NULL;
      stream->__bufsize = 0;
      stream->__userbuf = 1;
      break;
    case _IOLBF:	/* Line buffered.  */
      stream->__linebuf = 1;
    case _IOFBF:	/* Fully buffered.  */
      if (size == 0)
	{
	  __set_errno (EINVAL);
	  return EOF;
	}
      stream->__bufsize = size;
      if (buf != NULL)
	stream->__userbuf = 1;
      else if ((buf = (char *) malloc (size)) == NULL)
	return EOF;
      stream->__buffer = buf;
      break;
    }

  stream->__bufp = stream->__buffer;
  stream->__get_limit = stream->__buffer;
  /* The next output operation will prime the stream for writing.  */
  stream->__put_limit = stream->__buffer;

  return 0;
}