1 /*
2 * Copyright (c) 2000-2001, 2004 Proofpoint, Inc. and its suppliers.
3 * All rights reserved.
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 * By using this file, you agree to the terms and conditions set
11 * forth in the LICENSE file which can be found at the top level of
12 * the sendmail distribution.
13 */
14
15 #include <sm/gen.h>
16 SM_IDSTR(id, "@(#)$Id: ungetc.c,v 1.31 2013-11-22 20:51:44 ca Exp $")
17
18 #include <stdlib.h>
19 #include <string.h>
20 #include <signal.h>
21 #include <sm/time.h>
22 #include <errno.h>
23 #include <sm/io.h>
24 #include <sm/heap.h>
25 #include <sm/assert.h>
26 #include <sm/conf.h>
27 #include "local.h"
28
29 static void sm_submore_x __P((SM_FILE_T *));
30
31 /*
32 ** SM_SUBMORE_X -- expand ungetc buffer
33 **
34 ** Expand the ungetc buffer `in place'. That is, adjust fp->f_p when
35 ** the buffer moves, so that it points the same distance from the end,
36 ** and move the bytes in the buffer around as necessary so that they
37 ** are all at the end (stack-style).
38 **
39 ** Parameters:
40 ** fp -- the file pointer
41 **
42 ** Results:
43 ** none.
44 **
45 ** Exceptions:
46 ** F:sm_heap -- out of memory
47 */
48
49 static void
50 sm_submore_x(fp)
51 SM_FILE_T *fp;
52 {
53 register int i;
54 register unsigned char *p;
55
56 if (fp->f_ub.smb_base == fp->f_ubuf)
57 {
58 /* Get a buffer; f_ubuf is fixed size. */
59 p = sm_malloc_x((size_t) SM_IO_BUFSIZ);
60 fp->f_ub.smb_base = p;
61 fp->f_ub.smb_size = SM_IO_BUFSIZ;
62 p += SM_IO_BUFSIZ - sizeof(fp->f_ubuf);
63 for (i = sizeof(fp->f_ubuf); --i >= 0;)
64 p[i] = fp->f_ubuf[i];
65 fp->f_p = p;
66 return;
67 }
68 i = fp->f_ub.smb_size;
69 p = sm_realloc_x(fp->f_ub.smb_base, i << 1);
70
71 /* no overlap (hence can use memcpy) because we doubled the size */
72 (void) memcpy((void *) (p + i), (void *) p, (size_t) i);
73 fp->f_p = p + i;
74 fp->f_ub.smb_base = p;
75 fp->f_ub.smb_size = i << 1;
76 }
77
78 /*
79 ** SM_IO_UNGETC -- place a character back into the buffer just read
80 **
81 ** Parameters:
82 ** fp -- the file pointer affected
83 ** timeout -- time to complete ungetc
84 ** c -- the character to place back
85 **
86 ** Results:
87 ** On success, returns value of character placed back, 0-255.
88 ** Returns SM_IO_EOF if c == SM_IO_EOF or if last operation
89 ** was a write and flush failed.
90 **
91 ** Exceptions:
92 ** F:sm_heap -- out of memory
93 */
94
95 int
96 sm_io_ungetc(fp, timeout, c)
97 register SM_FILE_T *fp;
98 int timeout;
99 int c;
100 {
101 SM_REQUIRE_ISA(fp, SmFileMagic);
102 if (c == SM_IO_EOF)
103 return SM_IO_EOF;
104 if (timeout == SM_TIME_IMMEDIATE)
105 {
106 /*
107 ** Ungetting the buffer will take time and we are wanted to
108 ** return immediately. So...
109 */
110
111 errno = EAGAIN;
112 return SM_IO_EOF;
113 }
114
115 if (!Sm_IO_DidInit)
116 sm_init();
117 if ((fp->f_flags & SMRD) == 0)
118 {
119 /*
120 ** Not already reading: no good unless reading-and-writing.
121 ** Otherwise, flush any current write stuff.
122 */
123
124 if ((fp->f_flags & SMRW) == 0)
125 return SM_IO_EOF;
126 if (fp->f_flags & SMWR)
127 {
128 if (sm_flush(fp, &timeout))
129 return SM_IO_EOF;
130 fp->f_flags &= ~SMWR;
131 fp->f_w = 0;
132 fp->f_lbfsize = 0;
133 }
134 fp->f_flags |= SMRD;
135 }
136 c = (unsigned char) c;
137
138 /*
139 ** If we are in the middle of ungetc'ing, just continue.
140 ** This may require expanding the current ungetc buffer.
141 */
142
143 if (HASUB(fp))
144 {
145 if (fp->f_r >= fp->f_ub.smb_size)
146 sm_submore_x(fp);
147 *--fp->f_p = c;
148 fp->f_r++;
149 return c;
150 }
151 fp->f_flags &= ~SMFEOF;
152
153 /*
154 ** If we can handle this by simply backing up, do so,
155 ** but never replace the original character.
156 ** (This makes sscanf() work when scanning `const' data.)
157 */
158
159 if (fp->f_bf.smb_base != NULL && fp->f_p > fp->f_bf.smb_base &&
160 fp->f_p[-1] == c)
161 {
162 fp->f_p--;
163 fp->f_r++;
164 return c;
165 }
166
167 /*
168 ** Create an ungetc buffer.
169 ** Initially, we will use the `reserve' buffer.
170 */
171
172 fp->f_ur = fp->f_r;
173 fp->f_up = fp->f_p;
174 fp->f_ub.smb_base = fp->f_ubuf;
175 fp->f_ub.smb_size = sizeof(fp->f_ubuf);
176 fp->f_ubuf[sizeof(fp->f_ubuf) - 1] = c;
177 fp->f_p = &fp->f_ubuf[sizeof(fp->f_ubuf) - 1];
178 fp->f_r = 1;
179
180 return c;
181 }