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
43 static 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 */
51 static int
__submore(FILE * fp)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 */
86 int
ungetc(int c,FILE * fp)87 ungetc(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 */
103 int
__ungetc(int c,FILE * fp)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