File: | src/bin/dd/position.c |
Warning: | line 161, column 9 Although the value stored to 'n' is used in the enclosing expression, the value is never actually read from 'n' |
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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(*__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 | */ |
57 | void |
58 | pos_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 & (ISPIPE0x02|ISTAPE0x04)) && !isatty(in.fd)) { |
67 | if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR1) == -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 & ISPIPE0x02) { |
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_NOERROR0x00400) { |
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 | |
114 | void |
115 | pos_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 & ISTAPE0x04)) { |
127 | if (lseek(out.fd, out.offset * out.dbsz, SEEK_SET0) == -1) |
128 | err(1, "%s", out.name); |
129 | return; |
130 | } |
131 | |
132 | /* If no read access, try using mtio. */ |
133 | if (out.flags & NOREAD0x08) { |
134 | t_op.mt_op = MTFSR3; |
135 | t_op.mt_count = out.offset; |
136 | |
137 | if (ioctl(out.fd, MTIOCTOP((unsigned long)0x80000000 | ((sizeof(struct mtop) & 0x1fff ) << 16) | ((('m')) << 8) | ((1))), &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 = MTBSR4; |
156 | t_op.mt_count = 1; |
157 | if (ioctl(out.fd, MTIOCTOP((unsigned long)0x80000000 | ((sizeof(struct mtop) & 0x1fff ) << 16) | ((('m')) << 8) | ((1))), &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) |
Although the value stored to 'n' is used in the enclosing expression, the value is never actually read from 'n' | |
162 | err(1, "%s", out.name); |
163 | break; |
164 | } |
165 | } |