glibc/libio/filedoalloc.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. */

/*
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

/* Modified for GNU iostream by Per Bothner 1991, 1992. */

#ifndef _POSIX_SOURCE
# define _POSIX_SOURCE
#endif
#include "libioP.h"
#include <sys/types.h>
#include <sys/stat.h>
#ifdef __STDC__
#include <stdlib.h>
#endif
#ifdef _LIBC
# include <unistd.h>
#endif

/*
 * Allocate a file buffer, or switch to unbuffered I/O.
 * Per the ANSI C standard, ALL tty devices default to line buffered.
 *
 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
 * optimisation) right after the _fstat() that finds the buffer size.
 */

int
DEFUN(_IO_file_doallocate, (fp),
      register _IO_FILE *fp)
{
  register _IO_size_t size;
  int couldbetty;
  register char *p;
  struct stat st;

  /* If _IO_cleanup_registration_needed is non-zero, we should call the
     function it points to.  This is to make sure _IO_cleanup gets called
     on exit.  We call it from _IO_file_doallocate, since that is likely
     to get called by any program that does buffered I/O. */
  if (_IO_cleanup_registration_needed)
    (*_IO_cleanup_registration_needed)();
  
  if (fp->_fileno < 0 || _IO_SYSSTAT (fp, &st) < 0)
    {
      couldbetty = 0;
      size = _IO_BUFSIZ;
#if 0
      /* do not try to optimise fseek() */
      fp->_flags |= __SNPT;
#endif
    }
  else
    {
      couldbetty = S_ISCHR(st.st_mode);
#if _IO_HAVE_ST_BLKSIZE
      size = st.st_blksize <= 0 ? _IO_BUFSIZ : st.st_blksize;
#else
      size = _IO_BUFSIZ;
#endif
    }
  p = ALLOC_BUF(size);
  if (p == NULL)
    return EOF;
  _IO_setb(fp, p, p+size, 1);
  if (couldbetty && isatty(fp->_fileno))
    fp->_flags |= _IO_LINE_BUF;
  return 1;
}