libio/iosetvbuf.c

/* 
Copyright (C) 1993 Free Software Foundation

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

This 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 General Public License for more details.

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

As a special exception, if you link this library with files
compiled with a GNU compiler to produce an executable, this does not cause
the resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why
the executable file might be covered by the GNU General Public License. */

#include "libioP.h"

#define _IOFBF 0 /* Fully buffered. */
#define _IOLBF 1 /* Line buffered. */
#define _IONBF 2 /* No buffering. */

int
DEFUN(_IO_setvbuf, (fp, buf, mode, size),
      _IO_FILE* fp AND char* buf AND int mode AND _IO_size_t size)
{
  CHECK_FILE(fp, EOF);
  switch (mode)
    {
    case _IOFBF:
      fp->_IO_file_flags &= ~_IO_LINE_BUF|_IO_UNBUFFERED;
      if (buf == NULL)
	{
	  if (fp->_IO_buf_base == NULL)
	    {
	      /* There is no flag to distinguish between "fully buffered
		 mode has been explicitly set" as opposed to "line
		 buffering has not been explicitly set".  In both
		 cases, _IO_LINE_BUF is off.  If this is a tty, and
		 _IO_filedoalloc later gets called, it cannot know if
		 it should set the _IO_LINE_BUF flag (because that is
		 the default), or not (because we have explicitly asked
		 for fully buffered mode).  So we make sure a buffer
		 gets allocated now, and explicitly turn off line
		 buffering.

		 A possibly cleaner alternative would be to add an
		 extra flag, but then flags are a finite resource.  */
	      if (_IO_DOALLOCATE (fp) < 0)
		return EOF;
	      fp->_IO_file_flags &= ~_IO_LINE_BUF;
	    }
	  return 0;
	}
      break;
    case _IOLBF:
      fp->_IO_file_flags &= ~_IO_UNBUFFERED;
      fp->_IO_file_flags |= _IO_LINE_BUF;
      if (buf == NULL)
	return 0;
      break;
    case _IONBF:
      buf = NULL;
      size = 0;
      break;
    default:
      return EOF;
    }
  return _IO_SETBUF (fp, buf, size) == NULL ? EOF : 0;
}