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.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 & (ISPIPE|ISTAPE)) && !isatty(in.fd)) { 67 if (lseek(in.fd, 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 } 113 114 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 & ISTAPE)) { 127 if (lseek(out.fd, 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) == -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 = 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 } 166