2 * Copyright (c) 1991, 1993, 1994
3 * The Regents of the University of California. All rights reserved.
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.
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
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 * 3. 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.
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
33 * @(#)position.c 8.3 (Berkeley) 4/2/94
34 * $FreeBSD: src/bin/dd/position.c,v 1.17.2.2 2001/01/23 14:23:55 asmodai Exp $
35 * $DragonFly: src/bin/dd/position.c,v 1.4 2008/01/28 16:08:02 matthias Exp $
38 #include <sys/types.h>
49 * Position input/output data streams before starting the copy. Device type
50 * dependent. Seekable devices use lseek, and the rest position by reading.
51 * Seeking past the end of file can cause null blocks to be written to the
62 /* If known to be seekable, try to seek on it. */
63 if (in.flags & ISSEEK) {
65 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
67 err(1, "%s", in.name);
71 /* Don't try to read a really weird amount (like negative). */
73 errx(1, "%s: illegal offset", "iseek/skip");
76 * Read the data. If a pipe, read until satisfy the number of bytes
77 * being skipped. No differentiation for reading complete and partial
78 * blocks for other devices.
80 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
81 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
82 if (in.flags & ISPIPE) {
97 errx(1, "skip reached end of input");
101 * Input error -- either EOF with no more files, or I/O error.
102 * If noerror not set die. POSIX requires that the warning
103 * message be followed by an I/O display.
105 if (ddflags & C_NOERROR) {
113 err(1, "%s", in.name);
125 * If not a tape, try seeking on the file. Seeking on a pipe is
126 * going to fail, but don't protect the user -- they shouldn't
127 * have specified the seek operand.
129 if (out.flags & (ISSEEK | ISPIPE)) {
131 if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
133 err(1, "%s", out.name);
137 /* Don't try to read a really weird amount (like negative). */
139 errx(1, "%s: illegal offset", "oseek/seek");
141 /* If no read access, try using mtio. */
142 if (out.flags & NOREAD) {
144 t_op.mt_count = out.offset;
146 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
147 err(1, "%s", out.name);
152 for (cnt = 0; cnt < out.offset; ++cnt) {
153 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
157 err(1, "%s", out.name);
160 * If reach EOF, fill with NUL characters; first, back up over
161 * the EOF mark. Note, cnt has not yet been incremented, so
162 * the EOF read does not count as a seek'd block.
166 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
167 err(1, "%s", out.name);
169 while (cnt++ < out.offset) {
170 n = write(out.fd, out.db, out.dbsz);
172 err(1, "%s", out.name);
173 if ((size_t)n != out.dbsz)
174 errx(1, "%s: write failure", out.name);