2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by the University of
19 * California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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37 #if defined(LIBC_SCCS) && !defined(lint)
39 static char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93";
41 static const char rcsid[] =
42 "$FreeBSD: src/lib/libc/stdio/ungetc.c,v 1.7.2.1 2001/03/05 11:27:49 obrien Exp $";
43 #endif /* LIBC_SCCS and not lint */
49 #include "libc_private.h"
51 static int __submore __P((FILE *));
54 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when
55 * the buffer moves, so that it points the same distance from the end,
56 * and move the bytes in the buffer around as necessary so that they
57 * are all at the end (stack-style).
65 if (fp->_ub._base == fp->_ubuf) {
67 * Get a new buffer (rather than expanding the old one).
69 if ((p = malloc((size_t)BUFSIZ)) == NULL)
72 fp->_ub._size = BUFSIZ;
73 p += BUFSIZ - sizeof(fp->_ubuf);
74 for (i = sizeof(fp->_ubuf); --i >= 0;)
80 p = realloc(fp->_ub._base, (size_t)(i << 1));
83 /* no overlap (hence can use memcpy) because we doubled the size */
84 (void)memcpy((void *)(p + i), (void *)p, (size_t)i);
87 fp->_ub._size = i << 1;
92 ungetc(int c, FILE *fp)
99 if ((fp->_flags & __SRD) == 0) {
101 * Not already reading: no good unless reading-and-writing.
102 * Otherwise, flush any current write stuff.
104 if ((fp->_flags & __SRW) == 0) {
108 if (fp->_flags & __SWR) {
113 fp->_flags &= ~__SWR;
119 c = (unsigned char)c;
122 * If we are in the middle of ungetc'ing, just continue.
123 * This may require expanding the current ungetc buffer.
126 if (fp->_r >= fp->_ub._size && __submore(fp)) {
135 fp->_flags &= ~__SEOF;
138 * If we can handle this by simply backing up, do so,
139 * but never replace the original character.
140 * (This makes sscanf() work when scanning `const' data.)
142 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base &&
151 * Create an ungetc buffer.
152 * Initially, we will use the `reserve' buffer.
156 fp->_ub._base = fp->_ubuf;
157 fp->_ub._size = sizeof(fp->_ubuf);
158 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;
159 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];