bin/dd/position.c

   1 /*      $OpenBSD: position.c,v 1.10 2009/10/27 23:59:21 deraadt Exp $   */
   2 /*      $NetBSD: position.c,v 1.4 1995/03/21 09:04:12 cgd Exp $ */
   3
   4 /*-
   5  * Copyright (c) 1991, 1993, 1994
   6  *      The Regents of the University of California.  All rights reserved.
   7  *
   8  * This code is derived from software contributed to Berkeley by
   9  * Keith Muller of the University of California, San Diego and Lance
  10  * Visser of Convex Computer Corporation.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, this list of conditions and the following disclaimer.
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in the
  19  *    documentation and/or other materials provided with the distribution.
  20  * 3. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #include <sys/types.h>
  38 #include <sys/stat.h>
  39 #include <sys/ioctl.h>
  40 #include <sys/mtio.h>
  41 #include <sys/time.h>
  42
  43 #include <err.h>
  44 #include <errno.h>
  45 #include <string.h>
  46 #include <unistd.h>
  47
  48 #include "dd.h"
  49 #include "extern.h"
  50
  51 /*
  52  * Position input/output data streams before starting the copy.  Device type
  53  * dependent.  Seekable devices use lseek, and the rest position by reading.
  54  * Seeking past the end of file can cause null blocks to be written to the
  55  * output.
  56  */
  57 void
  58 pos_in(void)
  59 {
  60         size_t bcnt;
  61         ssize_t nr;
  62         off_t cnt;
  63         int warned;
  64
  65         /* If not a pipe, tape or tty device, try to seek on it. */
  66         if (!(in.flags & (ISPIPE|ISTAPE)) && !isatty(in.fd)) {
  67                 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1)
  68                         err(1, "%s", in.name);
  69                 return;
  70         }
  71
  72         /*
  73          * Read the data.  If a pipe, read until satisfy the number of bytes
  74          * being skipped.  No differentiation for reading complete and partial
  75          * blocks for other devices.
  76          */
  77         for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
  78                 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
  79                         if (in.flags & ISPIPE) {
  80                                 if (!(bcnt -= nr)) {
  81                                         bcnt = in.dbsz;
  82                                         --cnt;
  83                                 }
  84                         } else
  85                                 --cnt;
  86                         continue;
  87                 }
  88
  89                 if (nr == 0) {
  90                         if (files_cnt > 1) {
  91                                 --files_cnt;
  92                                 continue;
  93                         }
  94                         errx(1, "skip reached end of input");
  95                 }
  96
  97                 /*
  98                  * Input error -- either EOF with no more files, or I/O error.
  99                  * If noerror not set die.  POSIX requires that the warning
 100                  * message be followed by an I/O display.
 101                  */
 102                 if (ddflags & C_NOERROR) {
 103                         if (!warned) {
 104                                 warn("%s", in.name);
 105                                 warned = 1;
 106                                 summary();
 107                         }
 108                         continue;
 109                 }
 110                 err(1, "%s", in.name);
 111         }
 112 }
 113
 114 void
 115 pos_out(void)
 116 {
 117         struct mtop t_op;
 118         off_t cnt;
 119         ssize_t 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, out.offset * out.dbsz, SEEK_SET) == -1)
 128                         err(1, "%s", out.name);
 129                 return;
 130         }
 131
 132         /* If no read access, try using mtio. */
 133         if (out.flags & NOREAD) {
 134                 t_op.mt_op = MTFSR;
 135                 t_op.mt_count = out.offset;
 136
 137                 if (ioctl(out.fd, MTIOCTOP, &t_op) < 0)
 138                         err(1, "%s", out.name);
 139                 return;
 140         }
 141
 142         /* Read it. */
 143         for (cnt = 0; cnt < out.offset; ++cnt) {
 144                 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
 145                         continue;
 146
 147                 if (n < 0)
 148                         err(1, "%s", out.name);
 149
 150                 /*
 151                  * If reach EOF, fill with NUL characters; first, back up over
 152                  * the EOF mark.  Note, cnt has not yet been incremented, so
 153                  * the EOF read does not count as a seek'd block.
 154                  */
 155                 t_op.mt_op = MTBSR;
 156                 t_op.mt_count = 1;
 157                 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
 158                         err(1, "%s", out.name);
 159
 160                 while (cnt++ < out.offset)
 161                         if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz)
 162                                 err(1, "%s", out.name);
 163                 break;
 164         }
 165 }