1 /* $NetBSD: position.c,v 1.6 1997/07/25 06:46:24 phil 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 #include <sys/cdefs.h> 41 #ifndef lint 42 #if 0 43 static char sccsid[] = "@(#)position.c 8.3 (Berkeley) 4/2/94"; 44 #else 45 __RCSID("$NetBSD: position.c,v 1.6 1997/07/25 06:46:24 phil 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 54 #include <err.h> 55 #include <errno.h> 56 #include <string.h> 57 #include <unistd.h> 58 59 #include "dd.h" 60 #include "extern.h" 61 62 /* 63 * Position input/output data streams before starting the copy. Device type 64 * dependent. Seekable devices use lseek, and the rest position by reading. 65 * Seeking past the end of file can cause null blocks to be written to the 66 * output. 67 */ 68 void 69 pos_in() 70 { 71 int bcnt, cnt, nr, warned; 72 73 /* If not a character, pipe or tape device, try to seek on it. */ 74 if (!(in.flags & (ISCHR|ISPIPE|ISTAPE))) { 75 if (lseek(in.fd, (off_t)in.offset * (off_t)in.dbsz, SEEK_CUR) 76 == -1) 77 err(1, "%s", in.name); 78 return; 79 } 80 81 /* 82 * Read the data. If a pipe, read until satisfy the number of bytes 83 * being skipped. No differentiation for reading complete and partial 84 * blocks for other devices. 85 */ 86 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) { 87 if ((nr = read(in.fd, in.db, bcnt)) > 0) { 88 if (in.flags & ISPIPE) { 89 if (!(bcnt -= nr)) { 90 bcnt = in.dbsz; 91 --cnt; 92 } 93 } else 94 --cnt; 95 continue; 96 } 97 98 if (nr == 0) { 99 if (files_cnt > 1) { 100 --files_cnt; 101 continue; 102 } 103 errx(1, "skip reached end of input"); 104 } 105 106 /* 107 * Input error -- either EOF with no more files, or I/O error. 108 * If noerror not set die. POSIX requires that the warning 109 * message be followed by an I/O display. 110 */ 111 if (ddflags & C_NOERROR) { 112 if (!warned) { 113 warn("%s", in.name); 114 warned = 1; 115 summary(); 116 } 117 continue; 118 } 119 err(1, "%s", in.name); 120 } 121 } 122 123 void 124 pos_out() 125 { 126 struct mtop t_op; 127 int cnt, n; 128 129 /* 130 * If not a tape, try seeking on the file. Seeking on a pipe is 131 * going to fail, but don't protect the user -- they shouldn't 132 * have specified the seek operand. 133 */ 134 if (!(out.flags & ISTAPE)) { 135 if (lseek(out.fd, 136 (off_t)out.offset * (off_t)out.dbsz, SEEK_SET) == -1) 137 err(1, "%s", out.name); 138 return; 139 } 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) < 0) 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 < 0) 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 if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz) 171 err(1, "%s", out.name); 172 break; 173 } 174 } 175