position.c revision 1.9 
1/*	$OpenBSD: position.c,v 1.9 2006/11/07 18:47:46 otto Exp $	*/
2/*	$NetBSD: position.c,v 1.4 1995/03/21 09:04:12 cgd Exp $	*/
3
4/*-
5 * Copyright (c) 1991, 1993, 1994
6 *	The Regents of the University of California.  All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * Keith Muller of the University of California, San Diego and Lance
10 * Visser of Convex Computer Corporation.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 *    notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 *    notice, this list of conditions and the following disclaimer in the
19 *    documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#ifndef lint
38#if 0
39static char sccsid[] = "@(#)position.c	8.3 (Berkeley) 4/2/94";
40#else
41static char rcsid[] = "$OpenBSD: position.c,v 1.9 2006/11/07 18:47:46 otto Exp $";
42#endif
43#endif /* not lint */
44
45#include <sys/types.h>
46#include <sys/stat.h>
47#include <sys/ioctl.h>
48#include <sys/mtio.h>
49#include <sys/time.h>
50
51#include <err.h>
52#include <errno.h>
53#include <string.h>
54#include <unistd.h>
55
56#include "dd.h"
57#include "extern.h"
58
59/*
60 * Position input/output data streams before starting the copy.  Device type
61 * dependent.  Seekable devices use lseek, and the rest position by reading.
62 * Seeking past the end of file can cause null blocks to be written to the
63 * output.
64 */
65void
66pos_in(void)
67{
68	size_t bcnt;
69	ssize_t nr;
70	off_t cnt;
71	int warned;
72
73	/* If not a pipe, tape or tty device, try to seek on it. */
74	if (!(in.flags & (ISPIPE|ISTAPE)) && !isatty(in.fd)) {
75		if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1)
76			err(1, "%s", in.name);
77		return;
78	}
79
80	/*
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.
84	 */
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) {
88				if (!(bcnt -= nr)) {
89					bcnt = in.dbsz;
90					--cnt;
91				}
92			} else
93				--cnt;
94			continue;
95		}
96
97		if (nr == 0) {
98			if (files_cnt > 1) {
99				--files_cnt;
100				continue;
101			}
102			errx(1, "skip reached end of input");
103		}
104
105		/*
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.
109		 */
110		if (ddflags & C_NOERROR) {
111			if (!warned) {
112				warn("%s", in.name);
113				warned = 1;
114				summary();
115			}
116			continue;
117		}
118		err(1, "%s", in.name);
119	}
120}
121
122void
123pos_out(void)
124{
125	struct mtop t_op;
126	off_t cnt;
127	ssize_t n;
128
129	/*
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.
133	 */
134	if (!(out.flags & ISTAPE)) {
135		if (lseek(out.fd, out.offset * out.dbsz, SEEK_SET) == -1)
136			err(1, "%s", out.name);
137		return;
138	}
139
140	/* If no read access, try using mtio. */
141	if (out.flags & NOREAD) {
142		t_op.mt_op = MTFSR;
143		t_op.mt_count = out.offset;
144
145		if (ioctl(out.fd, MTIOCTOP, &t_op) < 0)
146			err(1, "%s", out.name);
147		return;
148	}
149
150	/* Read it. */
151	for (cnt = 0; cnt < out.offset; ++cnt) {
152		if ((n = read(out.fd, out.db, out.dbsz)) > 0)
153			continue;
154
155		if (n < 0)
156			err(1, "%s", out.name);
157
158		/*
159		 * If reach EOF, fill with NUL characters; first, back up over
160		 * the EOF mark.  Note, cnt has not yet been incremented, so
161		 * the EOF read does not count as a seek'd block.
162		 */
163		t_op.mt_op = MTBSR;
164		t_op.mt_count = 1;
165		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
166			err(1, "%s", out.name);
167
168		while (cnt++ < out.offset)
169			if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz)
170				err(1, "%s", out.name);
171		break;
172	}
173}
174