1 /*
2 * Copyright (c) 2000-2001, 2004 Sendmail, 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 #pragma ident "%Z%%M% %I% %E% SMI"
16
17 #include <sm/gen.h>
18 SM_IDSTR(id, "@(#)$Id: ungetc.c,v 1.30 2005/06/14 23:07:20 ca Exp $")
19
20 #include <stdlib.h>
21 #include <string.h>
22 #include <signal.h>
23 #include <sm/time.h>
24 #include <errno.h>
25 #include <sm/io.h>
26 #include <sm/heap.h>
27 #include <sm/assert.h>
28 #include <sm/conf.h>
29 #include "local.h"
30
31 static void sm_submore_x __P((SM_FILE_T *));
32
33 /*
34 ** SM_SUBMORE_X -- expand ungetc buffer
35 **
36 ** Expand the ungetc buffer `in place'. That is, adjust fp->f_p when
37 ** the buffer moves, so that it points the same distance from the end,
38 ** and move the bytes in the buffer around as necessary so that they
39 ** are all at the end (stack-style).
40 **
41 ** Parameters:
42 ** fp -- the file pointer
43 **
44 ** Results:
45 ** none.
46 **
47 ** Exceptions:
48 ** F:sm_heap -- out of memory
49 */
50
51 static void
52 sm_submore_x(fp)
53 SM_FILE_T *fp;
54 {
55 register int i;
56 register unsigned char *p;
57
58 if (fp->f_ub.smb_base == fp->f_ubuf)
59 {
60 /* Get a buffer; f_ubuf is fixed size. */
61 p = sm_malloc_x((size_t) SM_IO_BUFSIZ);
62 fp->f_ub.smb_base = p;
63 fp->f_ub.smb_size = SM_IO_BUFSIZ;
64 p += SM_IO_BUFSIZ - sizeof(fp->f_ubuf);
65 for (i = sizeof(fp->f_ubuf); --i >= 0;)
66 p[i] = fp->f_ubuf[i];
67 fp->f_p = p;
68 return;
69 }
70 i = fp->f_ub.smb_size;
71 p = sm_realloc_x(fp->f_ub.smb_base, i << 1);
72
73 /* no overlap (hence can use memcpy) because we doubled the size */
74 (void) memcpy((void *) (p + i), (void *) p, (size_t) i);
75 fp->f_p = p + i;
76 fp->f_ub.smb_base = p;
77 fp->f_ub.smb_size = i << 1;
78 }
79
80 /*
81 ** SM_IO_UNGETC -- place a character back into the buffer just read
82 **
83 ** Parameters:
84 ** fp -- the file pointer affected
85 ** timeout -- time to complete ungetc
86 ** c -- the character to place back
87 **
88 ** Results:
89 ** On success, returns value of character placed back, 0-255.
90 ** Returns SM_IO_EOF if c == SM_IO_EOF or if last operation
91 ** was a write and flush failed.
92 **
93 ** Exceptions:
94 ** F:sm_heap -- out of memory
95 */
96
97 int
98 sm_io_ungetc(fp, timeout, c)
99 register SM_FILE_T *fp;
100 int timeout;
101 int c;
102 {
103 SM_REQUIRE_ISA(fp, SmFileMagic);
104 if (c == SM_IO_EOF)
105 return SM_IO_EOF;
106 if (timeout == SM_TIME_IMMEDIATE)
107 {
108 /*
109 ** Ungetting the buffer will take time and we are wanted to
110 ** return immediately. So...
111 */
112
113 errno = EAGAIN;
114 return SM_IO_EOF;
115 }
116
117 if (!Sm_IO_DidInit)
118 sm_init();
119 if ((fp->f_flags & SMRD) == 0)
120 {
121 /*
122 ** Not already reading: no good unless reading-and-writing.
123 ** Otherwise, flush any current write stuff.
124 */
125
126 if ((fp->f_flags & SMRW) == 0)
127 return SM_IO_EOF;
128 if (fp->f_flags & SMWR)
129 {
130 if (sm_flush(fp, &timeout))
131 return SM_IO_EOF;
132 fp->f_flags &= ~SMWR;
133 fp->f_w = 0;
134 fp->f_lbfsize = 0;
135 }
136 fp->f_flags |= SMRD;
137 }
138 c = (unsigned char) c;
139
140 /*
141 ** If we are in the middle of ungetc'ing, just continue.
142 ** This may require expanding the current ungetc buffer.
143 */
144
145 if (HASUB(fp))
146 {
147 if (fp->f_r >= fp->f_ub.smb_size)
148 sm_submore_x(fp);
149 *--fp->f_p = c;
150 fp->f_r++;
151 return c;
152 }
153 fp->f_flags &= ~SMFEOF;
154
155 /*
156 ** If we can handle this by simply backing up, do so,
157 ** but never replace the original character.
158 ** (This makes sscanf() work when scanning `const' data.)
159 */
160
161 if (fp->f_bf.smb_base != NULL && fp->f_p > fp->f_bf.smb_base &&
162 fp->f_p[-1] == c)
163 {
164 fp->f_p--;
165 fp->f_r++;
166 return c;
167 }
168
169 /*
170 ** Create an ungetc buffer.
171 ** Initially, we will use the `reserve' buffer.
172 */
173
174 fp->f_ur = fp->f_r;
175 fp->f_up = fp->f_p;
176 fp->f_ub.smb_base = fp->f_ubuf;
177 fp->f_ub.smb_size = sizeof(fp->f_ubuf);
178 fp->f_ubuf[sizeof(fp->f_ubuf) - 1] = c;
179 fp->f_p = &fp->f_ubuf[sizeof(fp->f_ubuf) - 1];
180 fp->f_r = 1;
181
182 return c;
183 }