stdio/setvbuf.c

   1 /* Copyright (C) 1991, 1993 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 /* Make STREAM use the buffering method given in MODE.
  26    If MODE indicates full or line buffering, use BUF,
  27    a buffer of SIZE bytes; if BUF is NULL, malloc a buffer.  */
  28 int
  29 DEFUN(setvbuf, (stream, buf, mode, size),
  30       FILE *stream AND char *buf AND int mode AND size_t size)
  31 {
  32   if (!__validfp(stream))
  33     {
  34       errno = EINVAL;
  35       return EOF;
  36     }
  37
  38   /* The ANSI standard says setvbuf can only be called before any I/O is done,
  39      but we allow it to replace an old buffer, flushing it first.  */
  40   if (stream->__buffer != NULL)
  41     {
  42       (void) fflush(stream);
  43       /* Free the old buffer if it was malloc'd.  */
  44       if (!stream->__userbuf)
  45         free(stream->__buffer);
  46     }
  47
  48   stream->__get_limit = stream->__put_limit = NULL;
  49   stream->__bufp = stream->__buffer = NULL;
  50   stream->__userbuf = stream->__linebuf = stream->__linebuf_active = 0;
  51
  52   switch (mode)
  53     {
  54     default:
  55       errno = EINVAL;
  56       return EOF;
  57     case _IONBF:        /* Unbuffered.  */
  58       stream->__buffer = NULL;
  59       stream->__bufsize = 0;
  60       stream->__userbuf = 1;
  61       break;
  62     case _IOLBF:        /* Line buffered.  */
  63       stream->__linebuf = 1;
  64     case _IOFBF:        /* Fully buffered.  */
  65       if (size == 0)
  66         {
  67           errno = EINVAL;
  68           return EOF;
  69         }
  70       stream->__bufsize = size;
  71       if (buf != NULL)
  72         stream->__userbuf = 1;
  73       else if ((buf = (char *) malloc(size)) == NULL)
  74         return EOF;
  75       stream->__buffer = buf;
  76       break;
  77     }
  78
  79   stream->__bufp = stream->__buffer;
  80   stream->__get_limit = stream->__buffer;
  81   /* The next output operation will prime the stream for writing.  */
  82   stream->__put_limit = stream->__buffer;
  83
  84   return 0;
  85 }