bin/dd/position.c

   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  * @(#)position.c       8.3 (Berkeley) 4/2/94
  38  * $FreeBSD: src/bin/dd/position.c,v 1.17.2.2 2001/01/23 14:23:55 asmodai Exp $
  39  * $DragonFly: src/bin/dd/position.c,v 1.3 2003/09/28 16:39:13 hmp Exp $
  40  */
  41
  42 #include <sys/types.h>
  43 #include <sys/mtio.h>
  44
  45 #include <err.h>
  46 #include <errno.h>
  47 #include <unistd.h>
  48
  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(void)
  60 {
  61         off_t cnt;
  62         int warned;
  63         ssize_t nr;
  64         size_t bcnt;
  65
  66         /* If known to be seekable, try to seek on it. */
  67         if (in.flags & ISSEEK) {
  68                 errno = 0;
  69                 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
  70                     errno != 0)
  71                         err(1, "%s", in.name);
  72                 return;
  73         }
  74
  75         /* Don't try to read a really weird amount (like negative). */
  76         if (in.offset < 0)
  77                 errx(1, "%s: illegal offset", "iseek/skip");
  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
 121 void
 122 pos_out(void)
 123 {
 124         struct mtop t_op;
 125         off_t cnt;
 126         ssize_t n;
 127
 128         /*
 129          * If not a tape, try seeking on the file.  Seeking on a pipe is
 130          * going to fail, but don't protect the user -- they shouldn't
 131          * have specified the seek operand.
 132          */
 133         if (out.flags & (ISSEEK | ISPIPE)) {
 134                 errno = 0;
 135                 if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
 136                     errno != 0)
 137                         err(1, "%s", out.name);
 138                 return;
 139         }
 140
 141         /* Don't try to read a really weird amount (like negative). */
 142         if (out.offset < 0)
 143                 errx(1, "%s: illegal offset", "oseek/seek");
 144
 145         /* If no read access, try using mtio. */
 146         if (out.flags & NOREAD) {
 147                 t_op.mt_op = MTFSR;
 148                 t_op.mt_count = out.offset;
 149
 150                 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
 151                         err(1, "%s", out.name);
 152                 return;
 153         }
 154
 155         /* Read it. */
 156         for (cnt = 0; cnt < out.offset; ++cnt) {
 157                 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
 158                         continue;
 159
 160                 if (n == -1)
 161                         err(1, "%s", out.name);
 162
 163                 /*
 164                  * If reach EOF, fill with NUL characters; first, back up over
 165                  * the EOF mark.  Note, cnt has not yet been incremented, so
 166                  * the EOF read does not count as a seek'd block.
 167                  */
 168                 t_op.mt_op = MTBSR;
 169                 t_op.mt_count = 1;
 170                 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
 171                         err(1, "%s", out.name);
 172
 173                 while (cnt++ < out.offset) {
 174                         n = write(out.fd, out.db, out.dbsz);
 175                         if (n == -1)
 176                                 err(1, "%s", out.name);
 177                         if ((size_t)n != out.dbsz)
 178                                 errx(1, "%s: write failure", out.name);
 179                 }
 180                 break;
 181         }
 182 }