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 $
37 #include <sys/types.h>
48 * Position input/output data streams before starting the copy. Device type
49 * dependent. Seekable devices use lseek, and the rest position by reading.
50 * Seeking past the end of file can cause null blocks to be written to the
61 /* If known to be seekable, try to seek on it. */
62 if (in.flags & ISSEEK) {
64 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
66 err(1, "%s", in.name);
70 /* Don't try to read a really weird amount (like negative). */
72 errx(1, "%s: illegal offset", "iseek/skip");
75 * Read the data. If a pipe, read until satisfy the number of bytes
76 * being skipped. No differentiation for reading complete and partial
77 * blocks for other devices.
79 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
80 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
81 if (in.flags & ISPIPE) {
99 errx(1, "skip reached end of input");
103 * Input error -- either EOF with no more files, or I/O error.
104 * If noerror not set die. POSIX requires that the warning
105 * message be followed by an I/O display.
107 if (ddflags & C_NOERROR) {
115 err(1, "%s", in.name);
127 * If not a tape, try seeking on the file. Seeking on a pipe is
128 * going to fail, but don't protect the user -- they shouldn't
129 * have specified the seek operand.
131 if (out.flags & (ISSEEK | ISPIPE)) {
133 if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
135 err(1, "%s", out.name);
139 /* Don't try to read a really weird amount (like negative). */
141 errx(1, "%s: illegal offset", "oseek/seek");
143 /* If no read access, try using mtio. */
144 if (out.flags & NOREAD) {
146 t_op.mt_count = out.offset;
148 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
149 err(1, "%s", out.name);
154 for (cnt = 0; cnt < out.offset; ++cnt) {
155 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
159 err(1, "%s", out.name);
162 * If reach EOF, fill with NUL characters; first, back up over
163 * the EOF mark. Note, cnt has not yet been incremented, so
164 * the EOF read does not count as a seek'd block.
168 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
169 err(1, "%s", out.name);
171 while (cnt++ < out.offset) {
172 n = write(out.fd, out.db, out.dbsz);
174 err(1, "%s", out.name);
175 if ((size_t)n != out.dbsz)
176 errx(1, "%s: write failure", out.name);