dd/position.c

   1 /*      $NetBSD: position.c,v 1.6 1997/07/25 06:46:24 phil Exp $        */
   2
   3 /*-
   4  * Copyright (c) 1991, 1993, 1994
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Keith Muller of the University of California, San Diego and Lance
   9  * Visser of Convex Computer Corporation.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. All advertising materials mentioning features or use of this software
  20  *    must display the following acknowledgement:
  21  *      This product includes software developed by the University of
  22  *      California, Berkeley and its contributors.
  23  * 4. Neither the name of the University nor the names of its contributors
  24  *    may be used to endorse or promote products derived from this software
  25  *    without specific prior written permission.
  26  *
  27  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  28  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  29  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  31  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  35  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  37  * SUCH DAMAGE.
  38  */
  39
  40 #include <sys/cdefs.h>
  41 #ifndef lint
  42 #if 0
  43 static char sccsid[] = "@(#)position.c  8.3 (Berkeley) 4/2/94";
  44 #else
  45 __RCSID("$NetBSD: position.c,v 1.6 1997/07/25 06:46:24 phil Exp $");
  46 #endif
  47 #endif /* not lint */
  48
  49 #include <sys/types.h>
  50 #include <sys/stat.h>
  51 #include <sys/ioctl.h>
  52 #include <sys/mtio.h>
  53
  54 #include <err.h>
  55 #include <errno.h>
  56 #include <string.h>
  57 #include <unistd.h>
  58
  59 #include "dd.h"
  60 #include "extern.h"
  61
  62 /*
  63  * Position input/output data streams before starting the copy.  Device type
  64  * dependent.  Seekable devices use lseek, and the rest position by reading.
  65  * Seeking past the end of file can cause null blocks to be written to the
  66  * output.
  67  */
  68 void
  69 pos_in()
  70 {
  71         int bcnt, cnt, nr, warned;
  72
  73         /* If not a character, pipe or tape device, try to seek on it. */
  74         if (!(in.flags & (ISCHR|ISPIPE|ISTAPE))) {
  75                 if (lseek(in.fd, (off_t)in.offset * (off_t)in.dbsz, SEEK_CUR)
  76                     == -1)
  77                         err(1, "%s", in.name);
  78                 return;
  79         }
  80
  81         /*
  82          * Read the data.  If a pipe, read until satisfy the number of bytes
  83          * being skipped.  No differentiation for reading complete and partial
  84          * blocks for other devices.
  85          */
  86         for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
  87                 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
  88                         if (in.flags & ISPIPE) {
  89                                 if (!(bcnt -= nr)) {
  90                                         bcnt = in.dbsz;
  91                                         --cnt;
  92                                 }
  93                         } else
  94                                 --cnt;
  95                         continue;
  96                 }
  97
  98                 if (nr == 0) {
  99                         if (files_cnt > 1) {
 100                                 --files_cnt;
 101                                 continue;
 102                         }
 103                         errx(1, "skip reached end of input");
 104                 }
 105
 106                 /*
 107                  * Input error -- either EOF with no more files, or I/O error.
 108                  * If noerror not set die.  POSIX requires that the warning
 109                  * message be followed by an I/O display.
 110                  */
 111                 if (ddflags & C_NOERROR) {
 112                         if (!warned) {
 113                                 warn("%s", in.name);
 114                                 warned = 1;
 115                                 summary();
 116                         }
 117                         continue;
 118                 }
 119                 err(1, "%s", in.name);
 120         }
 121 }
 122
 123 void
 124 pos_out()
 125 {
 126         struct mtop t_op;
 127         int cnt, n;
 128
 129         /*
 130          * If not a tape, try seeking on the file.  Seeking on a pipe is
 131          * going to fail, but don't protect the user -- they shouldn't
 132          * have specified the seek operand.
 133          */
 134         if (!(out.flags & ISTAPE)) {
 135                 if (lseek(out.fd,
 136                     (off_t)out.offset * (off_t)out.dbsz, SEEK_SET) == -1)
 137                         err(1, "%s", out.name);
 138                 return;
 139         }
 140
 141         /* If no read access, try using mtio. */
 142         if (out.flags & NOREAD) {
 143                 t_op.mt_op = MTFSR;
 144                 t_op.mt_count = out.offset;
 145
 146                 if (ioctl(out.fd, MTIOCTOP, &t_op) < 0)
 147                         err(1, "%s", out.name);
 148                 return;
 149         }
 150
 151         /* Read it. */
 152         for (cnt = 0; cnt < out.offset; ++cnt) {
 153                 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
 154                         continue;
 155
 156                 if (n < 0)
 157                         err(1, "%s", out.name);
 158
 159                 /*
 160                  * If reach EOF, fill with NUL characters; first, back up over
 161                  * the EOF mark.  Note, cnt has not yet been incremented, so
 162                  * the EOF read does not count as a seek'd block.
 163                  */
 164                 t_op.mt_op = MTBSR;
 165                 t_op.mt_count = 1;
 166                 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
 167                         err(1, "%s", out.name);
 168
 169                 while (cnt++ < out.offset)
 170                         if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz)
 171                                 err(1, "%s", out.name);
 172                 break;
 173         }
 174 }