position.c revision 111629 
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
42#endif /* not lint */
43#include <sys/cdefs.h>
44__FBSDID("$FreeBSD: head/bin/dd/position.c 111629 2003-02-27 18:04:54Z markm $");
45
46#include <sys/types.h>
47#include <sys/mtio.h>
48
49#include <err.h>
50#include <errno.h>
51#include <inttypes.h>
52#include <unistd.h>
53
54#include "dd.h"
55#include "extern.h"
56
57/*
58 * Position input/output data streams before starting the copy.  Device type
59 * dependent.  Seekable devices use lseek, and the rest position by reading.
60 * Seeking past the end of file can cause null blocks to be written to the
61 * output.
62 */
63void
64pos_in(void)
65{
66	off_t cnt;
67	int warned;
68	ssize_t nr;
69	size_t bcnt;
70
71	/* If known to be seekable, try to seek on it. */
72	if (in.flags & ISSEEK) {
73		errno = 0;
74		if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
75		    errno != 0)
76			err(1, "%s", in.name);
77		return;
78	}
79
80	/* Don't try to read a really weird amount (like negative). */
81	if (in.offset < 0)
82		errx(1, "%s: illegal offset", "iseek/skip");
83
84	/*
85	 * Read the data.  If a pipe, read until satisfy the number of bytes
86	 * being skipped.  No differentiation for reading complete and partial
87	 * blocks for other devices.
88	 */
89	for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
90		if ((nr = read(in.fd, in.db, bcnt)) > 0) {
91			if (in.flags & ISPIPE) {
92				if (!(bcnt -= nr)) {
93					bcnt = in.dbsz;
94					--cnt;
95				}
96			} else
97				--cnt;
98			continue;
99		}
100
101		if (nr == 0) {
102			if (files_cnt > 1) {
103				--files_cnt;
104				continue;
105			}
106			errx(1, "skip reached end of input");
107		}
108
109		/*
110		 * Input error -- either EOF with no more files, or I/O error.
111		 * If noerror not set die.  POSIX requires that the warning
112		 * message be followed by an I/O display.
113		 */
114		if (ddflags & C_NOERROR) {
115			if (!warned) {
116				warn("%s", in.name);
117				warned = 1;
118				summary();
119			}
120			continue;
121		}
122		err(1, "%s", in.name);
123	}
124}
125
126void
127pos_out(void)
128{
129	struct mtop t_op;
130	off_t cnt;
131	ssize_t n;
132
133	/*
134	 * If not a tape, try seeking on the file.  Seeking on a pipe is
135	 * going to fail, but don't protect the user -- they shouldn't
136	 * have specified the seek operand.
137	 */
138	if (out.flags & (ISSEEK | ISPIPE)) {
139		errno = 0;
140		if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
141		    errno != 0)
142			err(1, "%s", out.name);
143		return;
144	}
145
146	/* Don't try to read a really weird amount (like negative). */
147	if (out.offset < 0)
148		errx(1, "%s: illegal offset", "oseek/seek");
149
150	/* If no read access, try using mtio. */
151	if (out.flags & NOREAD) {
152		t_op.mt_op = MTFSR;
153		t_op.mt_count = out.offset;
154
155		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
156			err(1, "%s", out.name);
157		return;
158	}
159
160	/* Read it. */
161	for (cnt = 0; cnt < out.offset; ++cnt) {
162		if ((n = read(out.fd, out.db, out.dbsz)) > 0)
163			continue;
164
165		if (n == -1)
166			err(1, "%s", out.name);
167
168		/*
169		 * If reach EOF, fill with NUL characters; first, back up over
170		 * the EOF mark.  Note, cnt has not yet been incremented, so
171		 * the EOF read does not count as a seek'd block.
172		 */
173		t_op.mt_op = MTBSR;
174		t_op.mt_count = 1;
175		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
176			err(1, "%s", out.name);
177
178		while (cnt++ < out.offset) {
179			n = write(out.fd, out.db, out.dbsz);
180			if (n == -1)
181				err(1, "%s", out.name);
182			if ((size_t)n != out.dbsz)
183				errx(1, "%s: write failure", out.name);
184		}
185		break;
186	}
187}
188