1  /* Copyright (C) 1993-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.
      17  
      18     As a special exception, if you link the code in this file with
      19     files compiled with a GNU compiler to produce an executable,
      20     that does not cause the resulting executable to be covered by
      21     the GNU Lesser General Public License.  This exception does not
      22     however invalidate any other reasons why the executable file
      23     might be covered by the GNU Lesser General Public License.
      24     This exception applies to code released by its copyright holders
      25     in files containing the exception.  */
      26  
      27  #include "libioP.h"
      28  
      29  #define _IOFBF 0 /* Fully buffered. */
      30  #define _IOLBF 1 /* Line buffered. */
      31  #define _IONBF 2 /* No buffering. */
      32  
      33  int
      34  _IO_setvbuf (FILE *fp, char *buf, int mode, size_t size)
      35  {
      36    int result;
      37    CHECK_FILE (fp, EOF);
      38    _IO_acquire_lock (fp);
      39    switch (mode)
      40      {
      41      case _IOFBF:
      42        fp->_flags &= ~(_IO_LINE_BUF|_IO_UNBUFFERED);
      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  		{
      62  		  result = EOF;
      63  		  goto unlock_return;
      64  		}
      65  	      fp->_flags &= ~_IO_LINE_BUF;
      66  	    }
      67  	  result = 0;
      68  	  goto unlock_return;
      69  	}
      70        break;
      71      case _IOLBF:
      72        fp->_flags &= ~_IO_UNBUFFERED;
      73        fp->_flags |= _IO_LINE_BUF;
      74        if (buf == NULL)
      75  	{
      76  	  result = 0;
      77  	  goto unlock_return;
      78  	}
      79        break;
      80      case _IONBF:
      81        fp->_flags &= ~_IO_LINE_BUF;
      82        fp->_flags |= _IO_UNBUFFERED;
      83        buf = NULL;
      84        size = 0;
      85        break;
      86      default:
      87        result = EOF;
      88        goto unlock_return;
      89      }
      90    result = _IO_SETBUF (fp, buf, size) == NULL ? EOF : 0;
      91  
      92  unlock_return:
      93    _IO_release_lock (fp);
      94    return result;
      95  }
      96  libc_hidden_def (_IO_setvbuf)
      97  
      98  weak_alias (_IO_setvbuf, setvbuf)