position.c revision 51212
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. All advertising materials mentioning features or use of this software 18 * must display the following acknowledgement: 19 * This product includes software developed by the University of 20 * California, Berkeley and its contributors. 21 * 4. Neither the name of the University nor the names of its contributors 22 * may be used to endorse or promote products derived from this software 23 * without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35 * SUCH DAMAGE. 36 */ 37 38#ifndef lint 39#if 0 40static char sccsid[] = "@(#)position.c 8.3 (Berkeley) 4/2/94"; 41#endif 42static const char rcsid[] = 43 "$FreeBSD: head/bin/dd/position.c 51212 1999-09-12 18:56:12Z green $"; 44#endif /* not lint */ 45 46#include <sys/types.h> 47#include <sys/mtio.h> 48 49#include <err.h> 50#include <errno.h> 51#include <unistd.h> 52 53#include "dd.h" 54#include "extern.h" 55 56/* 57 * Position input/output data streams before starting the copy. Device type 58 * dependent. Seekable devices use lseek, and the rest position by reading. 59 * Seeking past the end of file can cause null blocks to be written to the 60 * output. 61 */ 62void 63pos_in() 64{ 65 off_t cnt; 66 int warned; 67 ssize_t nr; 68 size_t bcnt; 69 70 /* If not a character, pipe or tape device, try to seek on it. */ 71 if (!(in.flags & (ISCHR|ISPIPE|ISTAPE)) || in.flags & ISSEEK) { 72 errno = 0; 73 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 && 74 errno != 0) 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 121void 122pos_out() 123{ 124 struct mtop t_op; 125 off_t cnt; 126 ssize_t n; 127 128 /* If not a character, pipe or tape device, try to seek on it. */ 129 if (!(out.flags & (ISCHR|ISPIPE|ISTAPE)) || out.flags & ISSEEK) { 130 errno = 0; 131 if (lseek(out.fd, out.offset * out.dbsz, SEEK_SET) == -1 && 132 errno != 0) 133 err(1, "%s", out.name); 134 return; 135 } 136 137 /* If no read access, try using mtio. */ 138 if (out.flags & NOREAD) { 139 t_op.mt_op = MTFSR; 140 t_op.mt_count = out.offset; 141 142 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 143 err(1, "%s", out.name); 144 return; 145 } 146 147 /* Read it. */ 148 for (cnt = 0; cnt < out.offset; ++cnt) { 149 if ((n = read(out.fd, out.db, out.dbsz)) > 0) 150 continue; 151 152 if (n == -1) 153 err(1, "%s", out.name); 154 155 /* 156 * If reach EOF, fill with NUL characters; first, back up over 157 * the EOF mark. Note, cnt has not yet been incremented, so 158 * the EOF read does not count as a seek'd block. 159 */ 160 t_op.mt_op = MTBSR; 161 t_op.mt_count = 1; 162 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 163 err(1, "%s", out.name); 164 165 while (cnt++ < out.offset) 166 if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz) 167 err(1, "%s", out.name); 168 break; 169 } 170} 171