| 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 | } |