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