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 static char sccsid[] = "@(#)position.c 8.3 (Berkeley) 4/2/94"; 40 #endif /* not lint */ 41 42 #include <sys/types.h> 43 #include <sys/stat.h> 44 #include <sys/ioctl.h> 45 #include <sys/mtio.h> 46 47 #include <err.h> 48 #include <errno.h> 49 #include <string.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 */ 61 void 62 pos_in() 63 { 64 int bcnt, cnt, nr, warned; 65 66 /* If not a character, pipe or tape device, try to seek on it. */ 67 if (!(in.flags & (ISCHR|ISPIPE|ISTAPE))) { 68 if (lseek(in.fd, (off_t)(in.offset * in.dbsz), SEEK_CUR) == -1) 69 err(1, "%s", in.name); 70 return; 71 } 72 73 /* 74 * Read the data. If a pipe, read until satisfy the number of bytes 75 * being skipped. No differentiation for reading complete and partial 76 * blocks for other devices. 77 */ 78 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) { 79 if ((nr = read(in.fd, in.db, bcnt)) > 0) { 80 if (in.flags & ISPIPE) { 81 if (!(bcnt -= nr)) { 82 bcnt = in.dbsz; 83 --cnt; 84 } 85 } else 86 --cnt; 87 continue; 88 } 89 90 if (nr == 0) { 91 if (files_cnt > 1) { 92 --files_cnt; 93 continue; 94 } 95 errx(1, "skip reached end of input"); 96 } 97 98 /* 99 * Input error -- either EOF with no more files, or I/O error. 100 * If noerror not set die. POSIX requires that the warning 101 * message be followed by an I/O display. 102 */ 103 if (ddflags & C_NOERROR) { 104 if (!warned) { 105 warn("%s", in.name); 106 warned = 1; 107 summary(); 108 } 109 continue; 110 } 111 err(1, "%s", in.name); 112 } 113 } 114 115 void 116 pos_out() 117 { 118 struct mtop t_op; 119 int cnt, n; 120 121 /* 122 * If not a tape, try seeking on the file. Seeking on a pipe is 123 * going to fail, but don't protect the user -- they shouldn't 124 * have specified the seek operand. 125 */ 126 if (!(out.flags & ISTAPE)) { 127 if (lseek(out.fd, 128 (off_t)out.offset * out.dbsz, SEEK_SET) == -1) 129 err(1, "%s", out.name); 130 return; 131 } 132 133 /* If no read access, try using mtio. */ 134 if (out.flags & NOREAD) { 135 t_op.mt_op = MTFSR; 136 t_op.mt_count = out.offset; 137 138 if (ioctl(out.fd, MTIOCTOP, &t_op) < 0) 139 err(1, "%s", out.name); 140 return; 141 } 142 143 /* Read it. */ 144 for (cnt = 0; cnt < out.offset; ++cnt) { 145 if ((n = read(out.fd, out.db, out.dbsz)) > 0) 146 continue; 147 148 if (n < 0) 149 err(1, "%s", out.name); 150 151 /* 152 * If reach EOF, fill with NUL characters; first, back up over 153 * the EOF mark. Note, cnt has not yet been incremented, so 154 * the EOF read does not count as a seek'd block. 155 */ 156 t_op.mt_op = MTBSR; 157 t_op.mt_count = 1; 158 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 159 err(1, "%s", out.name); 160 161 while (cnt++ < out.offset) 162 if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz) 163 err(1, "%s", out.name); 164 break; 165 } 166 } 167