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. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)position.c 8.3 (Berkeley) 4/2/94 34 * $FreeBSD: src/bin/dd/position.c,v 1.17.2.2 2001/01/23 14:23:55 asmodai Exp $ 35 * $DragonFly: src/bin/dd/position.c,v 1.4 2008/01/28 16:08:02 matthias Exp $ 36 */ 37 38 #include <sys/types.h> 39 #include <sys/mtio.h> 40 41 #include <err.h> 42 #include <errno.h> 43 #include <unistd.h> 44 45 #include "dd.h" 46 #include "extern.h" 47 48 /* 49 * Position input/output data streams before starting the copy. Device type 50 * dependent. Seekable devices use lseek, and the rest position by reading. 51 * Seeking past the end of file can cause null blocks to be written to the 52 * output. 53 */ 54 void 55 pos_in(void) 56 { 57 off_t cnt; 58 int warned; 59 ssize_t nr; 60 size_t bcnt; 61 62 /* If known to be seekable, try to seek on it. */ 63 if (in.flags & ISSEEK) { 64 errno = 0; 65 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 && 66 errno != 0) 67 err(1, "%s", in.name); 68 return; 69 } 70 71 /* Don't try to read a really weird amount (like negative). */ 72 if (in.offset < 0) 73 errx(1, "%s: illegal offset", "iseek/skip"); 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 } 116 117 void 118 pos_out(void) 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 & (ISSEEK | ISPIPE)) { 130 errno = 0; 131 if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 && 132 errno != 0) 133 err(1, "%s", out.name); 134 return; 135 } 136 137 /* Don't try to read a really weird amount (like negative). */ 138 if (out.offset < 0) 139 errx(1, "%s: illegal offset", "oseek/seek"); 140 141 /* If no read access, try using mtio. */ 142 if (out.flags & NOREAD) { 143 t_op.mt_op = MTFSR; 144 t_op.mt_count = out.offset; 145 146 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 147 err(1, "%s", out.name); 148 return; 149 } 150 151 /* Read it. */ 152 for (cnt = 0; cnt < out.offset; ++cnt) { 153 if ((n = read(out.fd, out.db, out.dbsz)) > 0) 154 continue; 155 156 if (n == -1) 157 err(1, "%s", out.name); 158 159 /* 160 * If reach EOF, fill with NUL characters; first, back up over 161 * the EOF mark. Note, cnt has not yet been incremented, so 162 * the EOF read does not count as a seek'd block. 163 */ 164 t_op.mt_op = MTBSR; 165 t_op.mt_count = 1; 166 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 167 err(1, "%s", out.name); 168 169 while (cnt++ < out.offset) { 170 n = write(out.fd, out.db, out.dbsz); 171 if (n == -1) 172 err(1, "%s", out.name); 173 if ((size_t)n != out.dbsz) 174 errx(1, "%s: write failure", out.name); 175 } 176 break; 177 } 178 } 179