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 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93";
37 #endif /* LIBC_SCCS and not lint */
38 #include "namespace.h"
39 #include <stdio.h>
40 #include <stdlib.h>
41 #include <string.h>
42 #include "un-namespace.h"
43 #include "local.h"
44 #include "libc_private.h"
45
46 static int __submore(FILE *);
47
48 /*
49 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when
50 * the buffer moves, so that it points the same distance from the end,
51 * and move the bytes in the buffer around as necessary so that they
52 * are all at the end (stack-style).
53 */
54 static int
__submore(FILE * fp)55 __submore(FILE *fp)
56 {
57 int i;
58 unsigned char *p;
59
60 if (fp->_ub._base == fp->_ubuf) {
61 /*
62 * Get a new buffer (rather than expanding the old one).
63 */
64 if ((p = malloc((size_t)BUFSIZ)) == NULL)
65 return (EOF);
66 fp->_ub._base = p;
67 fp->_ub._size = BUFSIZ;
68 p += BUFSIZ - sizeof(fp->_ubuf);
69 for (i = sizeof(fp->_ubuf); --i >= 0;)
70 p[i] = fp->_ubuf[i];
71 fp->_p = p;
72 return (0);
73 }
74 i = fp->_ub._size;
75 p = reallocarray(fp->_ub._base, i, 2);
76 if (p == NULL)
77 return (EOF);
78 /* no overlap (hence can use memcpy) because we doubled the size */
79 (void)memcpy((void *)(p + i), (void *)p, (size_t)i);
80 fp->_p = p + i;
81 fp->_ub._base = p;
82 fp->_ub._size = i * 2;
83 return (0);
84 }
85
86 /*
87 * MT-safe version
88 */
89 int
ungetc(int c,FILE * fp)90 ungetc(int c, FILE *fp)
91 {
92 int ret;
93
94 if (!__sdidinit)
95 __sinit();
96 FLOCKFILE_CANCELSAFE(fp);
97 ORIENT(fp, -1);
98 ret = __ungetc(c, fp);
99 FUNLOCKFILE_CANCELSAFE();
100 return (ret);
101 }
102
103 /*
104 * Non-MT-safe version
105 */
106 int
__ungetc(int c,FILE * fp)107 __ungetc(int c, FILE *fp)
108 {
109
110 if (c == EOF)
111 return (EOF);
112 if ((fp->_flags & __SRD) == 0) {
113 /*
114 * Not already reading: no good unless reading-and-writing.
115 * Otherwise, flush any current write stuff.
116 */
117 if ((fp->_flags & __SRW) == 0)
118 return (EOF);
119 if (fp->_flags & __SWR) {
120 if (__sflush(fp))
121 return (EOF);
122 fp->_flags &= ~__SWR;
123 fp->_w = 0;
124 fp->_lbfsize = 0;
125 }
126 fp->_flags |= __SRD;
127 }
128 c = (unsigned char)c;
129
130 /*
131 * If we are in the middle of ungetc'ing, just continue.
132 * This may require expanding the current ungetc buffer.
133 */
134 if (HASUB(fp)) {
135 if (fp->_r >= fp->_ub._size && __submore(fp))
136 return (EOF);
137 *--fp->_p = c;
138 fp->_r++;
139 return (c);
140 }
141 fp->_flags &= ~__SEOF;
142
143 /*
144 * If we can handle this by simply backing up, do so,
145 * but never replace the original character.
146 * (This makes sscanf() work when scanning `const' data.)
147 */
148 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base &&
149 fp->_p[-1] == c) {
150 fp->_p--;
151 fp->_r++;
152 return (c);
153 }
154
155 /*
156 * Create an ungetc buffer.
157 * Initially, we will use the `reserve' buffer.
158 */
159 fp->_ur = fp->_r;
160 fp->_up = fp->_p;
161 fp->_ub._base = fp->_ubuf;
162 fp->_ub._size = sizeof(fp->_ubuf);
163 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;
164 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];
165 fp->_r = 1;
166 return (c);
167 }
168