stdio/setvbuf.c

   1 /* Copyright (C) 1991, 1993, 1995, 1996, 1997 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <stddef.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <errno.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 setvbuf (stream, buf, mode, size)
  30      FILE *stream;
  31      char *buf;
  32      int mode;
  33      size_t size;
  34 {
  35   if (!__validfp (stream))
  36     {
  37       __set_errno (EINVAL);
  38       return EOF;
  39     }
  40
  41   /* The ANSI standard says setvbuf can only be called before any I/O is done,
  42      but we allow it to replace an old buffer, flushing it first.  */
  43   if (stream->__buffer != NULL)
  44     {
  45       (void) fflush (stream);
  46       /* Free the old buffer if it was malloc'd.  */
  47       if (!stream->__userbuf)
  48         free(stream->__buffer);
  49     }
  50
  51   stream->__get_limit = stream->__put_limit = NULL;
  52   stream->__bufp = stream->__buffer = NULL;
  53   stream->__userbuf = stream->__linebuf = stream->__linebuf_active = 0;
  54
  55   switch (mode)
  56     {
  57     default:
  58       __set_errno (EINVAL);
  59       return EOF;
  60     case _IONBF:        /* Unbuffered.  */
  61       stream->__buffer = NULL;
  62       stream->__bufsize = 0;
  63       stream->__userbuf = 1;
  64       break;
  65     case _IOLBF:        /* Line buffered.  */
  66       stream->__linebuf = 1;
  67     case _IOFBF:        /* Fully buffered.  */
  68       if (size == 0)
  69         {
  70           __set_errno (EINVAL);
  71           return EOF;
  72         }
  73       stream->__bufsize = size;
  74       if (buf != NULL)
  75         stream->__userbuf = 1;
  76       else if ((buf = (char *) malloc (size)) == NULL)
  77         return EOF;
  78       stream->__buffer = buf;
  79       break;
  80     }
  81
  82   stream->__bufp = stream->__buffer;
  83   stream->__get_limit = stream->__buffer;
  84   /* The next output operation will prime the stream for writing.  */
  85   stream->__put_limit = stream->__buffer;
  86
  87   return 0;
  88 }