1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#include "namespace.h"
36#include <stdio.h>
37#include <stdlib.h>
38#include <string.h>
39#include "un-namespace.h"
40#include "local.h"
41#include "libc_private.h"
42
43static int __submore(FILE *);
44
45/*
46 * Expand the ungetc buffer `in place'.  That is, adjust fp->_p when
47 * the buffer moves, so that it points the same distance from the end,
48 * and move the bytes in the buffer around as necessary so that they
49 * are all at the end (stack-style).
50 */
51static int
52__submore(FILE *fp)
53{
54	int i;
55	unsigned char *p;
56
57	if (fp->_ub._base == fp->_ubuf) {
58		/*
59		 * Get a new buffer (rather than expanding the old one).
60		 */
61		if ((p = malloc((size_t)BUFSIZ)) == NULL)
62			return (EOF);
63		fp->_ub._base = p;
64		fp->_ub._size = BUFSIZ;
65		p += BUFSIZ - sizeof(fp->_ubuf);
66		for (i = sizeof(fp->_ubuf); --i >= 0;)
67			p[i] = fp->_ubuf[i];
68		fp->_p = p;
69		return (0);
70	}
71	i = fp->_ub._size;
72	p = reallocarray(fp->_ub._base, i, 2);
73	if (p == NULL)
74		return (EOF);
75	/* no overlap (hence can use memcpy) because we doubled the size */
76	(void)memcpy((void *)(p + i), (void *)p, (size_t)i);
77	fp->_p = p + i;
78	fp->_ub._base = p;
79	fp->_ub._size = i * 2;
80	return (0);
81}
82
83/*
84 * MT-safe version
85 */
86int
87ungetc(int c, FILE *fp)
88{
89	int ret;
90
91	if (!__sdidinit)
92		__sinit();
93	FLOCKFILE_CANCELSAFE(fp);
94	ORIENT(fp, -1);
95	ret = __ungetc(c, fp);
96	FUNLOCKFILE_CANCELSAFE();
97	return (ret);
98}
99
100/*
101 * Non-MT-safe version
102 */
103int
104__ungetc(int c, FILE *fp)
105{
106
107	if (c == EOF)
108		return (EOF);
109	if ((fp->_flags & __SRD) == 0) {
110		/*
111		 * Not already reading: no good unless reading-and-writing.
112		 * Otherwise, flush any current write stuff.
113		 */
114		if ((fp->_flags & __SRW) == 0)
115			return (EOF);
116		if (fp->_flags & __SWR) {
117			if (__sflush(fp))
118				return (EOF);
119			fp->_flags &= ~__SWR;
120			fp->_w = 0;
121			fp->_lbfsize = 0;
122		}
123		fp->_flags |= __SRD;
124	}
125	c = (unsigned char)c;
126
127	/*
128	 * If we are in the middle of ungetc'ing, just continue.
129	 * This may require expanding the current ungetc buffer.
130	 */
131	if (HASUB(fp)) {
132		if (fp->_r >= fp->_ub._size && __submore(fp))
133			return (EOF);
134		*--fp->_p = c;
135		fp->_r++;
136		return (c);
137	}
138	fp->_flags &= ~__SEOF;
139
140	/*
141	 * If we can handle this by simply backing up, do so,
142	 * but never replace the original character.
143	 * (This makes sscanf() work when scanning `const' data.)
144	 */
145	if (fp->_bf._base != NULL && fp->_p > fp->_bf._base &&
146	    fp->_p[-1] == c) {
147		fp->_p--;
148		fp->_r++;
149		return (c);
150	}
151
152	/*
153	 * Create an ungetc buffer.
154	 * Initially, we will use the `reserve' buffer.
155	 */
156	fp->_ur = fp->_r;
157	fp->_up = fp->_p;
158	fp->_ub._base = fp->_ubuf;
159	fp->_ub._size = sizeof(fp->_ubuf);
160	fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;
161	fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];
162	fp->_r = 1;
163	return (c);
164}
165