libio/iosetvbuf.c

   1 /*
   2 Copyright (C) 1993 Free Software Foundation
   3
   4 This file is part of the GNU IO Library.  This library is free
   5 software; you can redistribute it and/or modify it under the
   6 terms of the GNU General Public License as published by the
   7 Free Software Foundation; either version 2, or (at your option)
   8 any later version.
   9
  10 This library is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this library; see the file COPYING.  If not, write to the Free
  17 Software Foundation, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  18
  19 As a special exception, if you link this library with files
  20 compiled with a GNU compiler to produce an executable, this does not cause
  21 the resulting executable to be covered by the GNU General Public License.
  22 This exception does not however invalidate any other reasons why
  23 the executable file might be covered by the GNU General Public License. */
  24
  25 #include "libioP.h"
  26
  27 #define _IOFBF 0 /* Fully buffered. */
  28 #define _IOLBF 1 /* Line buffered. */
  29 #define _IONBF 2 /* No buffering. */
  30
  31 int
  32 _IO_setvbuf (fp, buf, mode, size)
  33      _IO_FILE* fp;
  34      char* buf;
  35      int mode;
  36      _IO_size_t size;
  37 {
  38   CHECK_FILE (fp, EOF);
  39   switch (mode)
  40     {
  41     case _IOFBF:
  42       fp->_IO_file_flags &= ~_IO_LINE_BUF;
  43       if (buf == NULL)
  44         {
  45           if (fp->_IO_buf_base == NULL)
  46             {
  47               /* There is no flag to distinguish between "fully buffered
  48                  mode has been explicitly set" as opposed to "line
  49                  buffering has not been explicitly set".  In both
  50                  cases, _IO_LINE_BUF is off.  If this is a tty, and
  51                  _IO_filedoalloc later gets called, it cannot know if
  52                  it should set the _IO_LINE_BUF flag (because that is
  53                  the default), or not (because we have explicitly asked
  54                  for fully buffered mode).  So we make sure a buffer
  55                  gets allocated now, and explicitly turn off line
  56                  buffering.
  57
  58                  A possibly cleaner alternative would be to add an
  59                  extra flag, but then flags are a finite resource.  */
  60               if (_IO_DOALLOCATE (fp) < 0)
  61                 return EOF;
  62               fp->_IO_file_flags &= ~_IO_LINE_BUF;
  63             }
  64           return 0;
  65         }
  66       break;
  67     case _IOLBF:
  68       fp->_IO_file_flags |= _IO_LINE_BUF;
  69       if (buf == NULL)
  70         return 0;
  71       break;
  72     case _IONBF:
  73       buf = NULL;
  74       size = 0;
  75       break;
  76     default:
  77       return EOF;
  78     }
  79   return _IO_SETBUF (fp, buf, size) == NULL ? EOF : 0;
  80 }