1 /* $OpenBSD: position.c,v 1.7 2003/06/11 23:42:12 deraadt Exp $ */
2 /* $NetBSD: position.c,v 1.4 1995/03/21 09:04:12 cgd Exp $ */
3
4 /*-
5 * Copyright (c) 1991, 1993, 1994
6 * The Regents of the University of California. All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * Keith Muller of the University of California, San Diego and Lance
10 * Visser of Convex Computer Corporation.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37 #ifndef lint
38 #if 0
39 static char sccsid[] = "@(#)position.c 8.3 (Berkeley) 4/2/94";
40 #else
41 static char rcsid[] = "$OpenBSD: position.c,v 1.7 2003/06/11 23:42:12 deraadt Exp $";
42 #endif
43 #endif /* not lint */
44
45 #include <sys/types.h>
46 #include <sys/stat.h>
47 #include <sys/ioctl.h>
48 #include <sys/mtio.h>
49 #include <sys/time.h>
50
51 #include <err.h>
52 #include <errno.h>
53 #include <string.h>
54 #include <unistd.h>
55
56 #include "dd.h"
57 #include "extern.h"
58
59 /*
60 * Position input/output data streams before starting the copy. Device type
61 * dependent. Seekable devices use lseek, and the rest position by reading.
62 * Seeking past the end of file can cause null blocks to be written to the
63 * output.
64 */
65 void
pos_in(void)66 pos_in(void)
67 {
68 size_t bcnt;
69 ssize_t nr;
70 off_t cnt;
71 int warned;
72
73 /* If not a pipe or tape device, try to seek on it. */
74 if (!(in.flags & (ISPIPE|ISTAPE))) {
75 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1)
76 err(1, "%s", in.name);
77 return;
78 }
79
80 /*
81 * Read the data. If a pipe, read until satisfy the number of bytes
82 * being skipped. No differentiation for reading complete and partial
83 * blocks for other devices.
84 */
85 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
86 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
87 if (in.flags & ISPIPE) {
88 if (!(bcnt -= nr)) {
89 bcnt = in.dbsz;
90 --cnt;
91 }
92 } else
93 --cnt;
94 continue;
95 }
96
97 if (nr == 0) {
98 if (files_cnt > 1) {
99 --files_cnt;
100 continue;
101 }
102 errx(1, "skip reached end of input");
103 }
104
105 /*
106 * Input error -- either EOF with no more files, or I/O error.
107 * If noerror not set die. POSIX requires that the warning
108 * message be followed by an I/O display.
109 */
110 if (ddflags & C_NOERROR) {
111 if (!warned) {
112 warn("%s", in.name);
113 warned = 1;
114 summary();
115 }
116 continue;
117 }
118 err(1, "%s", in.name);
119 }
120 }
121
122 void
pos_out(void)123 pos_out(void)
124 {
125 struct mtop t_op;
126 off_t cnt;
127 ssize_t n;
128
129 /*
130 * If not a tape, try seeking on the file. Seeking on a pipe is
131 * going to fail, but don't protect the user -- they shouldn't
132 * have specified the seek operand.
133 */
134 if (!(out.flags & ISTAPE)) {
135 if (lseek(out.fd, out.offset * out.dbsz, SEEK_SET) == -1)
136 err(1, "%s", out.name);
137 return;
138 }
139
140 /* If no read access, try using mtio. */
141 if (out.flags & NOREAD) {
142 t_op.mt_op = MTFSR;
143 t_op.mt_count = out.offset;
144
145 if (ioctl(out.fd, MTIOCTOP, &t_op) < 0)
146 err(1, "%s", out.name);
147 return;
148 }
149
150 /* Read it. */
151 for (cnt = 0; cnt < out.offset; ++cnt) {
152 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
153 continue;
154
155 if (n < 0)
156 err(1, "%s", out.name);
157
158 /*
159 * If reach EOF, fill with NUL characters; first, back up over
160 * the EOF mark. Note, cnt has not yet been incremented, so
161 * the EOF read does not count as a seek'd block.
162 */
163 t_op.mt_op = MTBSR;
164 t_op.mt_count = 1;
165 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
166 err(1, "%s", out.name);
167
168 while (cnt++ < out.offset)
169 if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz)
170 err(1, "%s", out.name);
171 break;
172 }
173 }
174