libio/iosetvbuf.c

   1 /* Copyright (C) 1993, 1996, 1997, 1998 Free Software Foundation, Inc.
   2    This file is part of the GNU IO Library.
   3
   4    This library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU General Public License as
   6    published by the Free Software Foundation; either version 2, or (at
   7    your option) any later version.
   8
   9    This library is distributed in the hope that it will be useful, but
  10    WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this library; see the file COPYING.  If not, write to
  16    the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
  17    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
  21    not cause the resulting executable to be covered by the GNU General
  22    Public License.  This exception does not however invalidate any
  23    other reasons why the executable file might be covered by the GNU
  24    General Public License.  */
  25
  26 #include "libioP.h"
  27
  28 #define _IOFBF 0 /* Fully buffered. */
  29 #define _IOLBF 1 /* Line buffered. */
  30 #define _IONBF 2 /* No buffering. */
  31
  32 int
  33 _IO_setvbuf (fp, buf, mode, size)
  34      _IO_FILE *fp;
  35      char *buf;
  36      int mode;
  37      _IO_size_t size;
  38 {
  39   int result;
  40   CHECK_FILE (fp, EOF);
  41   _IO_cleanup_region_start ((void (*) __P ((void *))) _IO_funlockfile, fp);
  42   _IO_flockfile (fp);
  43   switch (mode)
  44     {
  45     case _IOFBF:
  46       fp->_IO_file_flags &= ~_IO_LINE_BUF|_IO_UNBUFFERED;
  47       if (buf == NULL)
  48         {
  49           if (fp->_IO_buf_base == NULL)
  50             {
  51               /* There is no flag to distinguish between "fully buffered
  52                  mode has been explicitly set" as opposed to "line
  53                  buffering has not been explicitly set".  In both
  54                  cases, _IO_LINE_BUF is off.  If this is a tty, and
  55                  _IO_filedoalloc later gets called, it cannot know if
  56                  it should set the _IO_LINE_BUF flag (because that is
  57                  the default), or not (because we have explicitly asked
  58                  for fully buffered mode).  So we make sure a buffer
  59                  gets allocated now, and explicitly turn off line
  60                  buffering.
  61
  62                  A possibly cleaner alternative would be to add an
  63                  extra flag, but then flags are a finite resource.  */
  64               if (_IO_DOALLOCATE (fp) < 0)
  65                 {
  66                   result = EOF;
  67                   goto unlock_return;
  68                 }
  69               fp->_IO_file_flags &= ~_IO_LINE_BUF;
  70             }
  71           result = 0;
  72           goto unlock_return;
  73         }
  74       break;
  75     case _IOLBF:
  76       fp->_IO_file_flags &= ~_IO_UNBUFFERED;
  77       fp->_IO_file_flags |= _IO_LINE_BUF;
  78       if (buf == NULL)
  79         {
  80           result = 0;
  81           goto unlock_return;
  82         }
  83       break;
  84     case _IONBF:
  85       buf = NULL;
  86       size = 0;
  87       break;
  88     default:
  89       result = EOF;
  90       goto unlock_return;
  91     }
  92   result = _IO_SETBUF (fp, buf, size) == NULL ? EOF : 0;
  93 unlock_return:
  94   _IO_funlockfile (fp);
  95   _IO_cleanup_region_end (0);
  96   return result;
  97 }
  98
  99 #ifdef weak_alias
 100 weak_alias (_IO_setvbuf, setvbuf)
 101 #endif