1 /* $OpenBSD: position.c,v 1.4 2001/08/07 14:39:27 hugh 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. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the University of 23 * California, Berkeley and its contributors. 24 * 4. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 */ 40 41 #ifndef lint 42 #if 0 43 static char sccsid[] = "@(#)position.c 8.3 (Berkeley) 4/2/94"; 44 #else 45 static char rcsid[] = "$OpenBSD: position.c,v 1.4 2001/08/07 14:39:27 hugh Exp $"; 46 #endif 47 #endif /* not lint */ 48 49 #include <sys/types.h> 50 #include <sys/stat.h> 51 #include <sys/ioctl.h> 52 #include <sys/mtio.h> 53 #include <sys/time.h> 54 55 #include <err.h> 56 #include <errno.h> 57 #include <string.h> 58 #include <unistd.h> 59 60 #include "dd.h" 61 #include "extern.h" 62 63 /* 64 * Position input/output data streams before starting the copy. Device type 65 * dependent. Seekable devices use lseek, and the rest position by reading. 66 * Seeking past the end of file can cause null blocks to be written to the 67 * output. 68 */ 69 void 70 pos_in() 71 { 72 size_t bcnt; 73 ssize_t nr; 74 off_t cnt; 75 int warned; 76 77 /* If not a character, pipe or tape device, try to seek on it. */ 78 if (!(in.flags & (ISCHR|ISPIPE|ISTAPE))) { 79 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1) 80 err(1, "%s", in.name); 81 return; 82 } 83 84 /* 85 * Read the data. If a pipe, read until satisfy the number of bytes 86 * being skipped. No differentiation for reading complete and partial 87 * blocks for other devices. 88 */ 89 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) { 90 if ((nr = read(in.fd, in.db, bcnt)) > 0) { 91 if (in.flags & ISPIPE) { 92 if (!(bcnt -= nr)) { 93 bcnt = in.dbsz; 94 --cnt; 95 } 96 } else 97 --cnt; 98 continue; 99 } 100 101 if (nr == 0) { 102 if (files_cnt > 1) { 103 --files_cnt; 104 continue; 105 } 106 errx(1, "skip reached end of input"); 107 } 108 109 /* 110 * Input error -- either EOF with no more files, or I/O error. 111 * If noerror not set die. POSIX requires that the warning 112 * message be followed by an I/O display. 113 */ 114 if (ddflags & C_NOERROR) { 115 if (!warned) { 116 warn("%s", in.name); 117 warned = 1; 118 summary(); 119 } 120 continue; 121 } 122 err(1, "%s", in.name); 123 } 124 } 125 126 void 127 pos_out() 128 { 129 struct mtop t_op; 130 off_t cnt; 131 ssize_t n; 132 133 /* 134 * If not a tape, try seeking on the file. Seeking on a pipe is 135 * going to fail, but don't protect the user -- they shouldn't 136 * have specified the seek operand. 137 */ 138 if (!(out.flags & ISTAPE)) { 139 if (lseek(out.fd, out.offset * out.dbsz, SEEK_SET) == -1) 140 err(1, "%s", out.name); 141 return; 142 } 143 144 /* If no read access, try using mtio. */ 145 if (out.flags & NOREAD) { 146 t_op.mt_op = MTFSR; 147 t_op.mt_count = out.offset; 148 149 if (ioctl(out.fd, MTIOCTOP, &t_op) < 0) 150 err(1, "%s", out.name); 151 return; 152 } 153 154 /* Read it. */ 155 for (cnt = 0; cnt < out.offset; ++cnt) { 156 if ((n = read(out.fd, out.db, out.dbsz)) > 0) 157 continue; 158 159 if (n < 0) 160 err(1, "%s", out.name); 161 162 /* 163 * If reach EOF, fill with NUL characters; first, back up over 164 * the EOF mark. Note, cnt has not yet been incremented, so 165 * the EOF read does not count as a seek'd block. 166 */ 167 t_op.mt_op = MTBSR; 168 t_op.mt_count = 1; 169 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 170 err(1, "%s", out.name); 171 172 while (cnt++ < out.offset) 173 if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz) 174 err(1, "%s", out.name); 175 break; 176 } 177 } 178