stdio/newstream.c

   1 /* Copyright (C) 1991, 1992 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 Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 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 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <stddef.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23
  24
  25 /* Return a new, zeroed, stream.
  26    You must set its cookie and io_mode.
  27    The first operation will give it a buffer unless you do.
  28    It will also give it the default functions unless you set the `seen' flag.
  29    Returns NULL if a stream can't be created.  */
  30 FILE *
  31 DEFUN_VOID(__newstream)
  32 {
  33   register FILE *stream;
  34
  35   stream = __stdio_head;
  36   while (__validfp (stream))
  37     stream = stream->__next;
  38   if (stream == NULL)
  39     {
  40       /* None to reuse.  */
  41       stream = (FILE *) malloc (sizeof (FILE));
  42       if (stream == NULL)
  43         return NULL;
  44       stream->__next = __stdio_head;
  45       __stdio_head = stream;
  46     }
  47
  48   __invalidate (stream);
  49   stream->__magic = _IOMAGIC;
  50   stream->__offset = (fpos_t) -1;
  51   stream->__target = (fpos_t) -1;
  52
  53   return stream;
  54 }