1/*	$OpenBSD: position.c,v 1.11 2019/06/28 13:34:59 deraadt 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#include <sys/types.h>
38#include <sys/stat.h>
39#include <sys/ioctl.h>
40#include <sys/mtio.h>
41#include <sys/time.h>
42
43#include <err.h>
44#include <errno.h>
45#include <string.h>
46#include <unistd.h>
47
48#include "dd.h"
49#include "extern.h"
50
51/*
52 * Position input/output data streams before starting the copy.  Device type
53 * dependent.  Seekable devices use lseek, and the rest position by reading.
54 * Seeking past the end of file can cause null blocks to be written to the
55 * output.
56 */
57void
58pos_in(void)
59{
60	size_t bcnt;
61	ssize_t nr;
62	off_t cnt;
63	int warned;
64
65	/* If not a pipe, tape or tty device, try to seek on it. */
66	if (!(in.flags & (ISPIPE|ISTAPE)) && !isatty(in.fd)) {
67		if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1)
68			err(1, "%s", in.name);
69		return;
70	}
71
72	/*
73	 * Read the data.  If a pipe, read until satisfy the number of bytes
74	 * being skipped.  No differentiation for reading complete and partial
75	 * blocks for other devices.
76	 */
77	for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
78		if ((nr = read(in.fd, in.db, bcnt)) > 0) {
79			if (in.flags & ISPIPE) {
80				if (!(bcnt -= nr)) {
81					bcnt = in.dbsz;
82					--cnt;
83				}
84			} else
85				--cnt;
86			continue;
87		}
88
89		if (nr == 0) {
90			if (files_cnt > 1) {
91				--files_cnt;
92				continue;
93			}
94			errx(1, "skip reached end of input");
95		}
96
97		/*
98		 * Input error -- either EOF with no more files, or I/O error.
99		 * If noerror not set die.  POSIX requires that the warning
100		 * message be followed by an I/O display.
101		 */
102		if (ddflags & C_NOERROR) {
103			if (!warned) {
104				warn("%s", in.name);
105				warned = 1;
106				summary();
107			}
108			continue;
109		}
110		err(1, "%s", in.name);
111	}
112}
113
114void
115pos_out(void)
116{
117	struct mtop t_op;
118	off_t cnt;
119	ssize_t n;
120
121	/*
122	 * If not a tape, try seeking on the file.  Seeking on a pipe is
123	 * going to fail, but don't protect the user -- they shouldn't
124	 * have specified the seek operand.
125	 */
126	if (!(out.flags & ISTAPE)) {
127		if (lseek(out.fd, out.offset * out.dbsz, SEEK_SET) == -1)
128			err(1, "%s", out.name);
129		return;
130	}
131
132	/* If no read access, try using mtio. */
133	if (out.flags & NOREAD) {
134		t_op.mt_op = MTFSR;
135		t_op.mt_count = out.offset;
136
137		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
138			err(1, "%s", out.name);
139		return;
140	}
141
142	/* Read it. */
143	for (cnt = 0; cnt < out.offset; ++cnt) {
144		if ((n = read(out.fd, out.db, out.dbsz)) > 0)
145			continue;
146
147		if (n == -1)
148			err(1, "%s", out.name);
149
150		/*
151		 * If reach EOF, fill with NUL characters; first, back up over
152		 * the EOF mark.  Note, cnt has not yet been incremented, so
153		 * the EOF read does not count as a seek'd block.
154		 */
155		t_op.mt_op = MTBSR;
156		t_op.mt_count = 1;
157		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
158			err(1, "%s", out.name);
159
160		while (cnt++ < out.offset)
161			if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz)
162				err(1, "%s", out.name);
163		break;
164	}
165}
166