position.c revision 67451 
1/*-
2 * Copyright (c) 1991, 1993, 1994
3 *	The Regents of the University of California.  All rights reserved.
4 *
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.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
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.
24 *
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
35 * SUCH DAMAGE.
36 */
37
38#ifndef lint
39#if 0
40static char sccsid[] = "@(#)position.c	8.3 (Berkeley) 4/2/94";
41#endif
42static const char rcsid[] =
43  "$FreeBSD: head/bin/dd/position.c 67451 2000-10-22 23:00:32Z green $";
44#endif /* not lint */
45
46#include <sys/types.h>
47#include <sys/mtio.h>
48
49#include <err.h>
50#include <errno.h>
51#include <unistd.h>
52
53#include "dd.h"
54#include "extern.h"
55
56/*
57 * Position input/output data streams before starting the copy.  Device type
58 * dependent.  Seekable devices use lseek, and the rest position by reading.
59 * Seeking past the end of file can cause null blocks to be written to the
60 * output.
61 */
62void
63pos_in()
64{
65	off_t cnt;
66	int warned;
67	ssize_t nr;
68	size_t bcnt;
69
70	/* If known to be seekable, try to seek on it. */
71	if (in.flags & ISSEEK) {
72		errno = 0;
73		if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
74		    errno != 0)
75			err(1, "%s", in.name);
76		return;
77	}
78
79	/* Don't try to read a really weird amount (like negative). */
80	if (in.offset < 0)
81		errx(1, "%s: illegal offset", "iseek/skip");
82
83	/*
84	 * Read the data.  If a pipe, read until satisfy the number of bytes
85	 * being skipped.  No differentiation for reading complete and partial
86	 * blocks for other devices.
87	 */
88	for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
89		if ((nr = read(in.fd, in.db, bcnt)) > 0) {
90			if (in.flags & ISPIPE) {
91				if (!(bcnt -= nr)) {
92					bcnt = in.dbsz;
93					--cnt;
94				}
95			} else
96				--cnt;
97			continue;
98		}
99
100		if (nr == 0) {
101			if (files_cnt > 1) {
102				--files_cnt;
103				continue;
104			}
105			errx(1, "skip reached end of input");
106		}
107
108		/*
109		 * Input error -- either EOF with no more files, or I/O error.
110		 * If noerror not set die.  POSIX requires that the warning
111		 * message be followed by an I/O display.
112		 */
113		if (ddflags & C_NOERROR) {
114			if (!warned) {
115				warn("%s", in.name);
116				warned = 1;
117				summary();
118			}
119			continue;
120		}
121		err(1, "%s", in.name);
122	}
123}
124
125void
126pos_out()
127{
128	struct mtop t_op;
129	off_t cnt;
130	ssize_t n;
131
132	/*
133	 * If not a tape, try seeking on the file.  Seeking on a pipe is
134	 * going to fail, but don't protect the user -- they shouldn't
135	 * have specified the seek operand.
136	 */
137	if (out.flags & (ISSEEK | ISPIPE)) {
138		errno = 0;
139		if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
140		    errno != 0)
141			err(1, "%s", out.name);
142		return;
143	}
144
145	/* Don't try to read a really weird amount (like negative). */
146	if (out.offset < 0)
147		errx(1, "%s: illegal offset", "oseek/seek");
148
149	/* If no read access, try using mtio. */
150	if (out.flags & NOREAD) {
151		t_op.mt_op = MTFSR;
152		t_op.mt_count = out.offset;
153
154		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
155			err(1, "%s", out.name);
156		return;
157	}
158
159	/* Read it. */
160	for (cnt = 0; cnt < out.offset; ++cnt) {
161		if ((n = read(out.fd, out.db, out.dbsz)) > 0)
162			continue;
163
164		if (n == -1)
165			err(1, "%s", out.name);
166
167		/*
168		 * If reach EOF, fill with NUL characters; first, back up over
169		 * the EOF mark.  Note, cnt has not yet been incremented, so
170		 * the EOF read does not count as a seek'd block.
171		 */
172		t_op.mt_op = MTBSR;
173		t_op.mt_count = 1;
174		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
175			err(1, "%s", out.name);
176
177		while (cnt++ < out.offset) {
178			n = write(out.fd, out.db, out.dbsz);
179			if (n == -1)
180				err(1, "%s", out.name);
181			if ((size_t)n != out.dbsz)
182				errx(1, "%s: write failure", out.name);
183		}
184		break;
185	}
186}
187