1 /*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
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. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * @(#)ungetc.c 8.2 (Berkeley) 11/3/93
33 * $FreeBSD: src/lib/libc/stdio/ungetc.c,v 1.18 2008/04/17 22:17:54 jhb Exp $
34 */
35
36 #include "namespace.h"
37 #include <stdio.h>
38 #include <stdlib.h>
39 #include <string.h>
40 #include "un-namespace.h"
41 #include "local.h"
42 #include "libc_private.h"
43
44 static int __submore(FILE *);
45
46 /*
47 * Expand the ungetc buffer `in place'. That is, adjust fp->pub._p when
48 * the buffer moves, so that it points the same distance from the end,
49 * and move the bytes in the buffer around as necessary so that they
50 * are all at the end (stack-style).
51 */
52 static int
__submore(FILE * fp)53 __submore(FILE *fp)
54 {
55 int i;
56 unsigned char *p;
57
58 if (fp->_ub._base == fp->_ubuf) {
59 /*
60 * Get a new buffer (rather than expanding the old one).
61 */
62 if ((p = malloc((size_t)BUFSIZ)) == NULL)
63 return (EOF);
64 fp->_ub._base = p;
65 fp->_ub._size = BUFSIZ;
66 p += BUFSIZ - sizeof(fp->_ubuf);
67 for (i = sizeof(fp->_ubuf); --i >= 0;)
68 p[i] = fp->_ubuf[i];
69 fp->pub._p = p;
70 return (0);
71 }
72 i = fp->_ub._size;
73 p = realloc(fp->_ub._base, (size_t)(i << 1));
74 if (p == NULL)
75 return (EOF);
76 /* no overlap (hence can use memcpy) because we doubled the size */
77 memcpy((void *)(p + i), (void *)p, (size_t)i);
78 fp->pub._p = p + i;
79 fp->_ub._base = p;
80 fp->_ub._size = i << 1;
81 return (0);
82 }
83
84 /*
85 * MT-safe version
86 */
87 int
ungetc(int c,FILE * fp)88 ungetc(int c, FILE *fp)
89 {
90 int ret;
91
92 if (!__sdidinit)
93 __sinit();
94 FLOCKFILE(fp);
95 ORIENT(fp, -1);
96 ret = __ungetc(c, fp);
97 FUNLOCKFILE(fp);
98 return (ret);
99 }
100
101 /*
102 * Non-MT-safe version
103 */
104 int
__ungetc(int c,FILE * fp)105 __ungetc(int c, FILE *fp)
106 {
107 if (c == EOF)
108 return (EOF);
109 if ((fp->pub._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->pub._flags & __SRW) == 0)
115 return (EOF);
116 if (fp->pub._flags & __SWR) {
117 if (__sflush(fp))
118 return (EOF);
119 fp->pub._flags &= ~__SWR;
120 fp->pub._w = 0;
121 fp->pub._lbfsize = 0;
122 }
123 fp->pub._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->pub._r >= fp->_ub._size && __submore(fp))
133 return (EOF);
134 *--fp->pub._p = c;
135 fp->pub._r++;
136 return (c);
137 }
138 fp->pub._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->pub._p > fp->_bf._base &&
146 fp->pub._p[-1] == c) {
147 fp->pub._p--;
148 fp->pub._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->pub._r;
157 fp->_up = fp->pub._p;
158 fp->_ub._base = fp->_ubuf;
159 fp->_ub._size = sizeof(fp->_ubuf);
160 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;
161 fp->pub._p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];
162 fp->pub._r = 1;
163 return (c);
164 }
165