1 /* $NetBSD: position.c,v 1.4 1995/03/21 09:04:12 cgd Exp $ */ 2 3 /*- 4 * Copyright (c) 1991, 1993, 1994 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Keith Muller of the University of California, San Diego and Lance 9 * Visser of Convex Computer Corporation. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the University of 22 * California, Berkeley and its contributors. 23 * 4. Neither the name of the University nor the names of its contributors 24 * may be used to endorse or promote products derived from this software 25 * without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 37 * SUCH DAMAGE. 38 */ 39 40 #ifndef lint 41 #if 0 42 static char sccsid[] = "@(#)position.c 8.3 (Berkeley) 4/2/94"; 43 #else 44 static char rcsid[] = "$NetBSD: position.c,v 1.4 1995/03/21 09:04:12 cgd Exp $"; 45 #endif 46 #endif /* not lint */ 47 48 #include <sys/types.h> 49 #include <sys/stat.h> 50 #include <sys/ioctl.h> 51 #include <sys/mtio.h> 52 53 #include <err.h> 54 #include <errno.h> 55 #include <string.h> 56 #include <unistd.h> 57 58 #include "dd.h" 59 #include "extern.h" 60 61 /* 62 * Position input/output data streams before starting the copy. Device type 63 * dependent. Seekable devices use lseek, and the rest position by reading. 64 * Seeking past the end of file can cause null blocks to be written to the 65 * output. 66 */ 67 void 68 pos_in() 69 { 70 int bcnt, cnt, nr, warned; 71 72 /* If not a character, pipe or tape device, try to seek on it. */ 73 if (!(in.flags & (ISCHR|ISPIPE|ISTAPE))) { 74 if (lseek(in.fd, (off_t)(in.offset * in.dbsz), SEEK_CUR) == -1) 75 err(1, "%s", in.name); 76 return; 77 } 78 79 /* 80 * Read the data. If a pipe, read until satisfy the number of bytes 81 * being skipped. No differentiation for reading complete and partial 82 * blocks for other devices. 83 */ 84 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) { 85 if ((nr = read(in.fd, in.db, bcnt)) > 0) { 86 if (in.flags & ISPIPE) { 87 if (!(bcnt -= nr)) { 88 bcnt = in.dbsz; 89 --cnt; 90 } 91 } else 92 --cnt; 93 continue; 94 } 95 96 if (nr == 0) { 97 if (files_cnt > 1) { 98 --files_cnt; 99 continue; 100 } 101 errx(1, "skip reached end of input"); 102 } 103 104 /* 105 * Input error -- either EOF with no more files, or I/O error. 106 * If noerror not set die. POSIX requires that the warning 107 * message be followed by an I/O display. 108 */ 109 if (ddflags & C_NOERROR) { 110 if (!warned) { 111 warn("%s", in.name); 112 warned = 1; 113 summary(); 114 } 115 continue; 116 } 117 err(1, "%s", in.name); 118 } 119 } 120 121 void 122 pos_out() 123 { 124 struct mtop t_op; 125 int cnt, n; 126 127 /* 128 * If not a tape, try seeking on the file. Seeking on a pipe is 129 * going to fail, but don't protect the user -- they shouldn't 130 * have specified the seek operand. 131 */ 132 if (!(out.flags & ISTAPE)) { 133 if (lseek(out.fd, 134 (off_t)out.offset * out.dbsz, SEEK_SET) == -1) 135 err(1, "%s", out.name); 136 return; 137 } 138 139 /* If no read access, try using mtio. */ 140 if (out.flags & NOREAD) { 141 t_op.mt_op = MTFSR; 142 t_op.mt_count = out.offset; 143 144 if (ioctl(out.fd, MTIOCTOP, &t_op) < 0) 145 err(1, "%s", out.name); 146 return; 147 } 148 149 /* Read it. */ 150 for (cnt = 0; cnt < out.offset; ++cnt) { 151 if ((n = read(out.fd, out.db, out.dbsz)) > 0) 152 continue; 153 154 if (n < 0) 155 err(1, "%s", out.name); 156 157 /* 158 * If reach EOF, fill with NUL characters; first, back up over 159 * the EOF mark. Note, cnt has not yet been incremented, so 160 * the EOF read does not count as a seek'd block. 161 */ 162 t_op.mt_op = MTBSR; 163 t_op.mt_count = 1; 164 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 165 err(1, "%s", out.name); 166 167 while (cnt++ < out.offset) 168 if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz) 169 err(1, "%s", out.name); 170 break; 171 } 172 } 173