1 /*- 2 * Copyright (c) 1991 The Regents of the University of California. 3 * 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[] = "from: @(#)position.c 5.3 (Berkeley) 8/5/91";*/ 40 static char rcsid[] = "$Id: position.c,v 1.2 1993/08/01 19:00:06 mycroft Exp $"; 41 #endif /* not lint */ 42 43 #include <sys/types.h> 44 #include <sys/stat.h> 45 #include <sys/ioctl.h> 46 #include <sys/mtio.h> 47 #include <errno.h> 48 #include <unistd.h> 49 #include <string.h> 50 #include "dd.h" 51 #include "extern.h" 52 53 /* 54 * Position input/output data streams before starting the copy. Device type 55 * dependent. Seekable devices use lseek, and the rest position by reading. 56 * Seeking past the end of file can cause null blocks to be written to the 57 * output. 58 */ 59 void 60 pos_in() 61 { 62 register int bcnt, cnt, nr, warned; 63 64 /* If not a character, pipe or tape device, try to seek on it. */ 65 if (!(in.flags & (ISCHR|ISPIPE|ISTAPE))) { 66 if (lseek(in.fd, (off_t)(in.offset * in.dbsz), SEEK_CUR) == -1) 67 err("%s: %s", in.name, strerror(errno)); 68 return; 69 } 70 71 /* 72 * Read the data. If a pipe, read until satisfy the number of bytes 73 * being skipped. No differentiation for reading complete and partial 74 * blocks for other devices. 75 */ 76 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) { 77 if ((nr = read(in.fd, in.db, bcnt)) > 0) { 78 if (in.flags & ISPIPE) { 79 if (!(bcnt -= nr)) { 80 bcnt = in.dbsz; 81 --cnt; 82 } 83 } else 84 --cnt; 85 continue; 86 } 87 88 if (nr == 0) { 89 if (files_cnt > 1) { 90 --files_cnt; 91 continue; 92 } 93 err("skip reached end of input"); 94 } 95 96 /* 97 * Input error -- either EOF with no more files, or I/O error. 98 * If noerror not set die. POSIX requires that the warning 99 * message be followed by an I/O display. 100 */ 101 if (ddflags & C_NOERROR) { 102 if (!warned) { 103 warn("%s: %s", in.name, strerror(errno)); 104 warned = 1; 105 summary(0); 106 } 107 continue; 108 } 109 err("%s: %s", in.name, strerror(errno)); 110 } 111 } 112 113 void 114 pos_out() 115 { 116 register int cnt, n; 117 struct mtop t_op; 118 119 /* 120 * If not a tape, try seeking on the file. Seeking on a pipe is 121 * going to fail, but don't protect the user -- they shouldn't 122 * have specified the seek operand. 123 */ 124 if (!(out.flags & ISTAPE)) { 125 if (lseek(out.fd, 126 (off_t)out.offset * out.dbsz, SEEK_SET) == -1) 127 err("%s: %s", out.name, strerror(errno)); 128 return; 129 } 130 131 /* If no read access, try using mtio. */ 132 if (out.flags & NOREAD) { 133 t_op.mt_op = MTFSR; 134 t_op.mt_count = out.offset; 135 136 if (ioctl(out.fd, MTIOCTOP, &t_op) < 0) 137 err("%s: %s", out.name, strerror(errno)); 138 return; 139 } 140 141 /* Read it. */ 142 for (cnt = 0; cnt < out.offset; ++cnt) { 143 if ((n = read(out.fd, out.db, out.dbsz)) > 0) 144 continue; 145 146 if (n < 0) 147 err("%s: %s", out.name, strerror(errno)); 148 149 /* 150 * If reach EOF, fill with NUL characters; first, back up over 151 * the EOF mark. Note, cnt has not yet been incremented, so 152 * the EOF read does not count as a seek'd block. 153 */ 154 t_op.mt_op = MTBSR; 155 t_op.mt_count = 1; 156 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 157 err("%s: %s", out.name, strerror(errno)); 158 159 while (cnt++ < out.offset) 160 if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz) 161 err("%s: %s", out.name, strerror(errno)); 162 break; 163 } 164 } 165