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 * 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.
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
36 static char sccsid[] = "@(#)position.c 8.3 (Berkeley) 4/2/94";
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
42 #include <sys/types.h>
54 * Position input/output data streams before starting the copy. Device type
55 * dependent. Seekable devices use lseek, and the rest position by reading.
56 * Seeking past the end of file can cause null blocks to be written to the
67 /* If known to be seekable, try to seek on it. */
68 if (in.flags & ISSEEK) {
70 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
72 err(1, "%s", in.name);
76 /* Don't try to read a really weird amount (like negative). */
78 errx(1, "%s: illegal offset", "iseek/skip");
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.
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) {
102 errx(1, "skip reached end of input");
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.
110 if (ddflags & C_NOERROR) {
118 err(1, "%s", in.name);
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.
134 if (out.flags & (ISSEEK | ISPIPE)) {
136 if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
138 err(1, "%s", out.name);
142 /* Don't try to read a really weird amount (like negative). */
144 errx(1, "%s: illegal offset", "oseek/seek");
146 /* If no read access, try using mtio. */
147 if (out.flags & NOREAD) {
149 t_op.mt_count = out.offset;
151 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
152 err(1, "%s", out.name);
157 for (cnt = 0; cnt < out.offset; ++cnt) {
158 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
162 err(1, "%s", out.name);
165 * If reach EOF, fill with NUL characters; first, back up over
166 * the EOF mark. Note, cnt has not yet been incremented, so
167 * the EOF read does not count as a seek'd block.
171 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
172 err(1, "%s", out.name);
174 while (cnt++ < out.offset) {
175 n = write(out.fd, out.db, out.dbsz);
177 err(1, "%s", out.name);
178 if ((size_t)n != out.dbsz)
179 errx(1, "%s: write failure", out.name);