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>
64 _Static_assert(sizeof(io->offset) == sizeof(int64_t), "64-bit off_t");
67 * If the lseek offset will be negative, verify that this is a special
68 * device file. Some such files (e.g. /dev/kmem) permit "negative"
71 * Bail out if the calculation of a file offset would overflow.
73 if ((io->flags & ISCHR) == 0 && n > OFF_MAX / (ssize_t)sz)
74 errx(1, "seek offsets cannot be larger than %jd",
76 else if ((io->flags & ISCHR) != 0 && (uint64_t)n > UINT64_MAX / sz)
77 errx(1, "seek offsets cannot be larger than %ju",
78 (uintmax_t)UINT64_MAX);
80 return ((off_t)( (uint64_t)n * sz ));
84 * Position input/output data streams before starting the copy. Device type
85 * dependent. Seekable devices use lseek, and the rest position by reading.
86 * Seeking past the end of file can cause null blocks to be written to the
97 /* If known to be seekable, try to seek on it. */
98 if (in.flags & ISSEEK) {
100 if (lseek(in.fd, seek_offset(&in), SEEK_CUR) == -1 &&
102 err(1, "%s", in.name);
106 /* Don't try to read a really weird amount (like negative). */
108 errx(1, "%s: illegal offset", "iseek/skip");
111 * Read the data. If a pipe, read until satisfy the number of bytes
112 * being skipped. No differentiation for reading complete and partial
113 * blocks for other devices.
115 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
116 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
117 if (in.flags & ISPIPE) {
134 errx(1, "skip reached end of input");
138 * Input error -- either EOF with no more files, or I/O error.
139 * If noerror not set die. POSIX requires that the warning
140 * message be followed by an I/O display.
142 if (ddflags & C_NOERROR) {
150 err(1, "%s", in.name);
162 * If not a tape, try seeking on the file. Seeking on a pipe is
163 * going to fail, but don't protect the user -- they shouldn't
164 * have specified the seek operand.
166 if (out.flags & (ISSEEK | ISPIPE)) {
168 if (lseek(out.fd, seek_offset(&out), SEEK_CUR) == -1 &&
170 err(1, "%s", out.name);
174 /* Don't try to read a really weird amount (like negative). */
176 errx(1, "%s: illegal offset", "oseek/seek");
178 /* If no read access, try using mtio. */
179 if (out.flags & NOREAD) {
181 t_op.mt_count = out.offset;
183 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
184 err(1, "%s", out.name);
189 for (cnt = 0; cnt < out.offset; ++cnt) {
190 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
194 err(1, "%s", out.name);
197 * If reach EOF, fill with NUL characters; first, back up over
198 * the EOF mark. Note, cnt has not yet been incremented, so
199 * the EOF read does not count as a seek'd block.
203 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
204 err(1, "%s", out.name);
206 while (cnt++ < out.offset) {
207 n = write(out.fd, out.db, out.dbsz);
209 err(1, "%s", out.name);
210 if ((size_t)n != out.dbsz)
211 errx(1, "%s: write failure", out.name);