1 /*-
2 * Copyright (c) 1991, 1993, 1994
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Keith Muller of the University of California, San Diego and Lance
7 * Visser of Convex Computer Corporation.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 #ifndef lint
35 #if 0
36 static char sccsid[] = "@(#)position.c 8.3 (Berkeley) 4/2/94";
37 #endif
38 #endif /* not lint */
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
41
42 #include <sys/types.h>
43 #include <sys/mtio.h>
44
45 #include <err.h>
46 #include <errno.h>
47 #include <inttypes.h>
48 #include <signal.h>
49 #include <unistd.h>
50
51 #include "dd.h"
52 #include "extern.h"
53
54 /*
55 * Position input/output data streams before starting the copy. Device type
56 * dependent. Seekable devices use lseek, and the rest position by reading.
57 * Seeking past the end of file can cause null blocks to be written to the
58 * output.
59 */
60 void
pos_in(void)61 pos_in(void)
62 {
63 off_t cnt;
64 int warned;
65 ssize_t nr;
66 size_t bcnt;
67
68 /* If known to be seekable, try to seek on it. */
69 if (in.flags & ISSEEK) {
70 errno = 0;
71 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
72 errno != 0)
73 err(1, "%s", in.name);
74 return;
75 }
76
77 /* Don't try to read a really weird amount (like negative). */
78 if (in.offset < 0)
79 errx(1, "%s: illegal offset", "iseek/skip");
80
81 /*
82 * Read the data. If a pipe, read until satisfy the number of bytes
83 * being skipped. No differentiation for reading complete and partial
84 * blocks for other devices.
85 */
86 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
87 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
88 if (in.flags & ISPIPE) {
89 if (!(bcnt -= nr)) {
90 bcnt = in.dbsz;
91 --cnt;
92 }
93 } else
94 --cnt;
95 if (need_summary)
96 summary();
97 continue;
98 }
99
100 if (nr == 0) {
101 if (files_cnt > 1) {
102 --files_cnt;
103 continue;
104 }
105 errx(1, "skip reached end of input");
106 }
107
108 /*
109 * Input error -- either EOF with no more files, or I/O error.
110 * If noerror not set die. POSIX requires that the warning
111 * message be followed by an I/O display.
112 */
113 if (ddflags & C_NOERROR) {
114 if (!warned) {
115 warn("%s", in.name);
116 warned = 1;
117 summary();
118 }
119 continue;
120 }
121 err(1, "%s", in.name);
122 }
123 }
124
125 void
pos_out(void)126 pos_out(void)
127 {
128 struct mtop t_op;
129 off_t cnt;
130 ssize_t n;
131
132 /*
133 * If not a tape, try seeking on the file. Seeking on a pipe is
134 * going to fail, but don't protect the user -- they shouldn't
135 * have specified the seek operand.
136 */
137 if (out.flags & (ISSEEK | ISPIPE)) {
138 errno = 0;
139 if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
140 errno != 0)
141 err(1, "%s", out.name);
142 return;
143 }
144
145 /* Don't try to read a really weird amount (like negative). */
146 if (out.offset < 0)
147 errx(1, "%s: illegal offset", "oseek/seek");
148
149 /* If no read access, try using mtio. */
150 if (out.flags & NOREAD) {
151 t_op.mt_op = MTFSR;
152 t_op.mt_count = out.offset;
153
154 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
155 err(1, "%s", out.name);
156 return;
157 }
158
159 /* Read it. */
160 for (cnt = 0; cnt < out.offset; ++cnt) {
161 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
162 continue;
163
164 if (n == -1)
165 err(1, "%s", out.name);
166
167 /*
168 * If reach EOF, fill with NUL characters; first, back up over
169 * the EOF mark. Note, cnt has not yet been incremented, so
170 * the EOF read does not count as a seek'd block.
171 */
172 t_op.mt_op = MTBSR;
173 t_op.mt_count = 1;
174 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
175 err(1, "%s", out.name);
176
177 while (cnt++ < out.offset) {
178 n = write(out.fd, out.db, out.dbsz);
179 if (n == -1)
180 err(1, "%s", out.name);
181 if ((size_t)n != out.dbsz)
182 errx(1, "%s: write failure", out.name);
183 }
184 break;
185 }
186 }
187