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.
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49#include <unistd.h>
50
51#include "dd.h"
52#include "extern.h"
53
54/*
55 * Position input/output data streams before starting the copy. Device type
56 * dependent. Seekable devices use lseek, and the rest position by reading.
57 * Seeking past the end of file can cause null blocks to be written to the
58 * output.
59 */
60void
61pos_in()
62{
63 int bcnt, cnt, nr, warned;
64
65 /* If not a character, pipe or tape device, try to seek on it. */
66 if (!(in.flags & (ISCHR|ISPIPE|ISTAPE))) {
67 if (lseek(in.fd, (off_t)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()
116{
117 struct mtop t_op;
118 int cnt, n;
119
120 /*
121 * If not a tape, try seeking on the file. Seeking on a pipe is
122 * going to fail, but don't protect the user -- they shouldn't
123 * have specified the seek operand.
124 */
125 if (!(out.flags & ISTAPE)) {
126 if (lseek(out.fd,
127 (off_t)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) < 0)
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 < 0)
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}
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