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. All advertising materials mentioning features or use of this software
18 * must display the following acknowledgement:
19 * This product includes software developed by the University of
20 * California, Berkeley and its contributors.
21 * 4. Neither the name of the University nor the names of its contributors
22 * may be used to endorse or promote products derived from this software
23 * without specific prior written permission.
25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37 * @(#)position.c 8.3 (Berkeley) 4/2/94
38 * $FreeBSD: src/bin/dd/position.c,v 1.17.2.2 2001/01/23 14:23:55 asmodai Exp $
39 * $DragonFly: src/bin/dd/position.c,v 1.3 2003/09/28 14:39:13 hmp Exp $
42 #include <sys/types.h>
53 * Position input/output data streams before starting the copy. Device type
54 * dependent. Seekable devices use lseek, and the rest position by reading.
55 * Seeking past the end of file can cause null blocks to be written to the
66 /* If known to be seekable, try to seek on it. */
67 if (in.flags & ISSEEK) {
69 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
71 err(1, "%s", in.name);
75 /* Don't try to read a really weird amount (like negative). */
77 errx(1, "%s: illegal offset", "iseek/skip");
80 * Read the data. If a pipe, read until satisfy the number of bytes
81 * being skipped. No differentiation for reading complete and partial
82 * blocks for other devices.
84 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
85 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
86 if (in.flags & ISPIPE) {
101 errx(1, "skip reached end of input");
105 * Input error -- either EOF with no more files, or I/O error.
106 * If noerror not set die. POSIX requires that the warning
107 * message be followed by an I/O display.
109 if (ddflags & C_NOERROR) {
117 err(1, "%s", in.name);
129 * If not a tape, try seeking on the file. Seeking on a pipe is
130 * going to fail, but don't protect the user -- they shouldn't
131 * have specified the seek operand.
133 if (out.flags & (ISSEEK | ISPIPE)) {
135 if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
137 err(1, "%s", out.name);
141 /* Don't try to read a really weird amount (like negative). */
143 errx(1, "%s: illegal offset", "oseek/seek");
145 /* If no read access, try using mtio. */
146 if (out.flags & NOREAD) {
148 t_op.mt_count = out.offset;
150 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
151 err(1, "%s", out.name);
156 for (cnt = 0; cnt < out.offset; ++cnt) {
157 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
161 err(1, "%s", out.name);
164 * If reach EOF, fill with NUL characters; first, back up over
165 * the EOF mark. Note, cnt has not yet been incremented, so
166 * the EOF read does not count as a seek'd block.
170 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
171 err(1, "%s", out.name);
173 while (cnt++ < out.offset) {
174 n = write(out.fd, out.db, out.dbsz);
176 err(1, "%s", out.name);
177 if ((size_t)n != out.dbsz)
178 errx(1, "%s: write failure", out.name);