position.c revision 48026 
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	"$Id: position.c,v 1.8 1998/05/13 07:33:54 charnier Exp $";
44#endif /* not lint */
45
46#include <sys/types.h>
47#include <sys/mtio.h>
48
49#include <err.h>
50#include <unistd.h>
51
52#include "dd.h"
53#include "extern.h"
54
55/*
56 * Position input/output data streams before starting the copy.  Device type
57 * dependent.  Seekable devices use lseek, and the rest position by reading.
58 * Seeking past the end of file can cause null blocks to be written to the
59 * output.
60 */
61void
62pos_in()
63{
64	size_t bcnt;
65	ssize_t nr;
66	off_t cnt;
67	int warned;
68
69	/* If not a character, pipe or tape device, try to seek on it. */
70	if (!(in.flags & (ISCHR|ISPIPE|ISTAPE))) {
71		if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1)
72			err(1, "%s", in.name);
73		return;
74	}
75
76	/*
77	 * Read the data.  If a pipe, read until satisfy the number of bytes
78	 * being skipped.  No differentiation for reading complete and partial
79	 * blocks for other devices.
80	 */
81	for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
82		if ((nr = read(in.fd, in.db, bcnt)) > 0) {
83			if (in.flags & ISPIPE) {
84				if (!(bcnt -= nr)) {
85					bcnt = in.dbsz;
86					--cnt;
87				}
88			} else
89				--cnt;
90			continue;
91		}
92
93		if (nr == 0) {
94			if (files_cnt > 1) {
95				--files_cnt;
96				continue;
97			}
98			errx(1, "skip reached end of input");
99		}
100
101		/*
102		 * Input error -- either EOF with no more files, or I/O error.
103		 * If noerror not set die.  POSIX requires that the warning
104		 * message be followed by an I/O display.
105		 */
106		if (ddflags & C_NOERROR) {
107			if (!warned) {
108				warn("%s", in.name);
109				warned = 1;
110				summary();
111			}
112			continue;
113		}
114		err(1, "%s", in.name);
115	}
116}
117
118void
119pos_out()
120{
121	struct mtop t_op;
122	off_t cnt;
123	ssize_t n;
124
125	/*
126	 * If not a tape, try seeking on the file.  Seeking on a pipe is
127	 * going to fail, but don't protect the user -- they shouldn't
128	 * have specified the seek operand.
129	 */
130	if (!(out.flags & ISTAPE)) {
131		if (lseek(out.fd, out.offset * out.dbsz, SEEK_SET) == -1)
132			err(1, "%s", out.name);
133		return;
134	}
135
136	/* If no read access, try using mtio. */
137	if (out.flags & NOREAD) {
138		t_op.mt_op = MTFSR;
139		t_op.mt_count = out.offset;
140
141		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
142			err(1, "%s", out.name);
143		return;
144	}
145
146	/* Read it. */
147	for (cnt = 0; cnt < out.offset; ++cnt) {
148		if ((n = read(out.fd, out.db, out.dbsz)) > 0)
149			continue;
150
151		if (n == -1)
152			err(1, "%s", out.name);
153
154		/*
155		 * If reach EOF, fill with NUL characters; first, back up over
156		 * the EOF mark.  Note, cnt has not yet been incremented, so
157		 * the EOF read does not count as a seek'd block.
158		 */
159		t_op.mt_op = MTBSR;
160		t_op.mt_count = 1;
161		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
162			err(1, "%s", out.name);
163
164		while (cnt++ < out.offset)
165			if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz)
166				err(1, "%s", out.name);
167		break;
168	}
169}
170