position.c revision 48026
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 "$Id: position.c,v 1.8 1998/05/13 07:33:54 charnier Exp $"; 44#endif /* not lint */ 45 46#include <sys/types.h> 47#include <sys/mtio.h> 48 49#include <err.h> 50#include <unistd.h> 51 52#include "dd.h" 53#include "extern.h" 54 55/* 56 * Position input/output data streams before starting the copy. Device type 57 * dependent. Seekable devices use lseek, and the rest position by reading. 58 * Seeking past the end of file can cause null blocks to be written to the 59 * output. 60 */ 61void 62pos_in() 63{ 64 size_t bcnt; 65 ssize_t nr; 66 off_t cnt; 67 int warned; 68 69 /* If not a character, pipe or tape device, try to seek on it. */ 70 if (!(in.flags & (ISCHR|ISPIPE|ISTAPE))) { 71 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1) 72 err(1, "%s", in.name); 73 return; 74 } 75 76 /* 77 * Read the data. If a pipe, read until satisfy the number of bytes 78 * being skipped. No differentiation for reading complete and partial 79 * blocks for other devices. 80 */ 81 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) { 82 if ((nr = read(in.fd, in.db, bcnt)) > 0) { 83 if (in.flags & ISPIPE) { 84 if (!(bcnt -= nr)) { 85 bcnt = in.dbsz; 86 --cnt; 87 } 88 } else 89 --cnt; 90 continue; 91 } 92 93 if (nr == 0) { 94 if (files_cnt > 1) { 95 --files_cnt; 96 continue; 97 } 98 errx(1, "skip reached end of input"); 99 } 100 101 /* 102 * Input error -- either EOF with no more files, or I/O error. 103 * If noerror not set die. POSIX requires that the warning 104 * message be followed by an I/O display. 105 */ 106 if (ddflags & C_NOERROR) { 107 if (!warned) { 108 warn("%s", in.name); 109 warned = 1; 110 summary(); 111 } 112 continue; 113 } 114 err(1, "%s", in.name); 115 } 116} 117 118void 119pos_out() 120{ 121 struct mtop t_op; 122 off_t cnt; 123 ssize_t n; 124 125 /* 126 * If not a tape, try seeking on the file. Seeking on a pipe is 127 * going to fail, but don't protect the user -- they shouldn't 128 * have specified the seek operand. 129 */ 130 if (!(out.flags & ISTAPE)) { 131 if (lseek(out.fd, out.offset * out.dbsz, SEEK_SET) == -1) 132 err(1, "%s", out.name); 133 return; 134 } 135 136 /* If no read access, try using mtio. */ 137 if (out.flags & NOREAD) { 138 t_op.mt_op = MTFSR; 139 t_op.mt_count = out.offset; 140 141 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 142 err(1, "%s", out.name); 143 return; 144 } 145 146 /* Read it. */ 147 for (cnt = 0; cnt < out.offset; ++cnt) { 148 if ((n = read(out.fd, out.db, out.dbsz)) > 0) 149 continue; 150 151 if (n == -1) 152 err(1, "%s", out.name); 153 154 /* 155 * If reach EOF, fill with NUL characters; first, back up over 156 * the EOF mark. Note, cnt has not yet been incremented, so 157 * the EOF read does not count as a seek'd block. 158 */ 159 t_op.mt_op = MTBSR; 160 t_op.mt_count = 1; 161 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 162 err(1, "%s", out.name); 163 164 while (cnt++ < out.offset) 165 if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz) 166 err(1, "%s", out.name); 167 break; 168 } 169} 170