position.c revision 48051 
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	int bcnt, warned;
65	ssize_t nr;
66	off_t cnt;
67
68	/* If not a character, pipe or tape device, try to seek on it. */
69	if (!(in.flags & (ISCHR|ISPIPE|ISTAPE))) {
70		if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1)
71			err(1, "%s", in.name);
72		return;
73	}
74
75	/*
76	 * Read the data.  If a pipe, read until satisfy the number of bytes
77	 * being skipped.  No differentiation for reading complete and partial
78	 * blocks for other devices.
79	 */
80	for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
81		if ((nr = read(in.fd, in.db, bcnt)) > 0) {
82			if (in.flags & ISPIPE) {
83				if (!(bcnt -= nr)) {
84					bcnt = in.dbsz;
85					--cnt;
86				}
87			} else
88				--cnt;
89			continue;
90		}
91
92		if (nr == 0) {
93			if (files_cnt > 1) {
94				--files_cnt;
95				continue;
96			}
97			errx(1, "skip reached end of input");
98		}
99
100		/*
101		 * Input error -- either EOF with no more files, or I/O error.
102		 * If noerror not set die.  POSIX requires that the warning
103		 * message be followed by an I/O display.
104		 */
105		if (ddflags & C_NOERROR) {
106			if (!warned) {
107				warn("%s", in.name);
108				warned = 1;
109				summary();
110			}
111			continue;
112		}
113		err(1, "%s", in.name);
114	}
115}
116
117void
118pos_out()
119{
120	struct mtop t_op;
121	off_t cnt;
122	ssize_t n;
123
124	/*
125	 * If not a tape, try seeking on the file.  Seeking on a pipe is
126	 * going to fail, but don't protect the user -- they shouldn't
127	 * have specified the seek operand.
128	 */
129	if (!(out.flags & ISTAPE)) {
130		if (lseek(out.fd, out.offset * out.dbsz, SEEK_SET) == -1)
131			err(1, "%s", out.name);
132		return;
133	}
134
135	/* If no read access, try using mtio. */
136	if (out.flags & NOREAD) {
137		t_op.mt_op = MTFSR;
138		t_op.mt_count = out.offset;
139
140		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
141			err(1, "%s", out.name);
142		return;
143	}
144
145	/* Read it. */
146	for (cnt = 0; cnt < out.offset; ++cnt) {
147		if ((n = read(out.fd, out.db, out.dbsz)) > 0)
148			continue;
149
150		if (n == -1)
151			err(1, "%s", out.name);
152
153		/*
154		 * If reach EOF, fill with NUL characters; first, back up over
155		 * the EOF mark.  Note, cnt has not yet been incremented, so
156		 * the EOF read does not count as a seek'd block.
157		 */
158		t_op.mt_op = MTBSR;
159		t_op.mt_count = 1;
160		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
161			err(1, "%s", out.name);
162
163		while (cnt++ < out.offset)
164			if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz)
165				err(1, "%s", out.name);
166		break;
167	}
168}
169