stdio/setvbuf.c

   1 /* Copyright (C) 1991, 1993, 1995 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 #include <errno.h>
  24
  25
  26 /* Make STREAM use the buffering method given in MODE.
  27    If MODE indicates full or line buffering, use BUF,
  28    a buffer of SIZE bytes; if BUF is NULL, malloc a buffer.  */
  29 int
  30 DEFUN(setvbuf, (stream, buf, mode, size),
  31       FILE *stream AND char *buf AND int mode AND size_t size)
  32 {
  33   if (!__validfp(stream))
  34     {
  35       errno = EINVAL;
  36       return EOF;
  37     }
  38
  39   /* The ANSI standard says setvbuf can only be called before any I/O is done,
  40      but we allow it to replace an old buffer, flushing it first.  */
  41   if (stream->__buffer != NULL)
  42     {
  43       (void) fflush(stream);
  44       /* Free the old buffer if it was malloc'd.  */
  45       if (!stream->__userbuf)
  46         free(stream->__buffer);
  47     }
  48
  49   stream->__get_limit = stream->__put_limit = NULL;
  50   stream->__bufp = stream->__buffer = NULL;
  51   stream->__userbuf = stream->__linebuf = stream->__linebuf_active = 0;
  52
  53   switch (mode)
  54     {
  55     default:
  56       errno = EINVAL;
  57       return EOF;
  58     case _IONBF:        /* Unbuffered.  */
  59       stream->__buffer = NULL;
  60       stream->__bufsize = 0;
  61       stream->__userbuf = 1;
  62       break;
  63     case _IOLBF:        /* Line buffered.  */
  64       stream->__linebuf = 1;
  65     case _IOFBF:        /* Fully buffered.  */
  66       if (size == 0)
  67         {
  68           errno = EINVAL;
  69           return EOF;
  70         }
  71       stream->__bufsize = size;
  72       if (buf != NULL)
  73         stream->__userbuf = 1;
  74       else if ((buf = (char *) malloc(size)) == NULL)
  75         return EOF;
  76       stream->__buffer = buf;
  77       break;
  78     }
  79
  80   stream->__bufp = stream->__buffer;
  81   stream->__get_limit = stream->__buffer;
  82   /* The next output operation will prime the stream for writing.  */
  83   stream->__put_limit = stream->__buffer;
  84
  85   return 0;
  86 }