Update.
[glibc.git] / stdio / ungetc.c
blob34304aa3fd8d31145338a488bbc6c1b3d0fb482f
1 /* Copyright (C) 1991, 1993, 1996, 1997 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
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.
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.
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. */
19 #include <errno.h>
20 #include <stdio.h>
23 /* Push the character C back onto the input stream of STREAM. */
24 int
25 ungetc (c, stream)
26 int c;
27 FILE *stream;
29 if (!__validfp (stream) || !stream->__mode.__read)
31 __set_errno (EINVAL);
32 return EOF;
35 if (c == EOF)
36 return EOF;
38 if (stream->__pushed_back)
39 /* There is already a char pushed back. */
40 return EOF;
42 if ((stream->__linebuf_active || stream->__put_limit > stream->__buffer) &&
43 /* This is a read-write stream with something in its buffer.
44 Flush the stream. */
45 __flshfp (stream, EOF) == EOF)
46 return EOF;
48 stream->__pushback = (unsigned char) c;
49 /* Tell __fillbf we've pushed back a char. */
50 stream->__pushed_back = 1;
51 stream->__pushback_bufp = stream->__bufp;
52 /* Make the next getc call __fillbf. It will return C. */
53 stream->__bufp = stream->__get_limit;
55 /* We just gave it another character to read, so it's not at EOF. */
56 stream->__eof = 0;
58 return stream->__pushback;