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. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)position.c       8.3 (Berkeley) 4/2/94
  34  * $FreeBSD: src/bin/dd/position.c,v 1.17.2.2 2001/01/23 14:23:55 asmodai Exp $
  35  * $DragonFly: src/bin/dd/position.c,v 1.4 2008/01/28 16:08:02 matthias Exp $
  36  */
  37
  38 #include <sys/types.h>
  39 #include <sys/mtio.h>
  40
  41 #include <err.h>
  42 #include <errno.h>
  43 #include <unistd.h>
  44
  45 #include "dd.h"
  46 #include "extern.h"
  47
  48 /*
  49  * Position input/output data streams before starting the copy.  Device type
  50  * dependent.  Seekable devices use lseek, and the rest position by reading.
  51  * Seeking past the end of file can cause null blocks to be written to the
  52  * output.
  53  */
  54 void
  55 pos_in(void)
  56 {
  57         off_t cnt;
  58         int warned;
  59         ssize_t nr;
  60         size_t bcnt;
  61
  62         /* If known to be seekable, try to seek on it. */
  63         if (in.flags & ISSEEK) {
  64                 errno = 0;
  65                 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
  66                     errno != 0)
  67                         err(1, "%s", in.name);
  68                 return;
  69         }
  70
  71         /* Don't try to read a really weird amount (like negative). */
  72         if (in.offset < 0)
  73                 errx(1, "%s: illegal offset", "iseek/skip");
  74
  75         /*
  76          * Read the data.  If a pipe, read until satisfy the number of bytes
  77          * being skipped.  No differentiation for reading complete and partial
  78          * blocks for other devices.
  79          */
  80         for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
  81                 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
  82                         if (in.flags & ISPIPE) {
  83                                 if (!(bcnt -= nr)) {
  84                                         bcnt = in.dbsz;
  85                                         --cnt;
  86                                 }
  87                         } else
  88                                 --cnt;
  89                         continue;
  90                 }
  91
  92                 if (nr == 0) {
  93                         if (files_cnt > 1) {
  94                                 --files_cnt;
  95                                 continue;
  96                         }
  97                         errx(1, "skip reached end of input");
  98                 }
  99
 100                 /*
 101                  * Input error -- either EOF with no more files, or I/O error.
 102                  * If noerror not set die.  POSIX requires that the warning
 103                  * message be followed by an I/O display.
 104                  */
 105                 if (ddflags & C_NOERROR) {
 106                         if (!warned) {
 107                                 warn("%s", in.name);
 108                                 warned = 1;
 109                                 summary();
 110                         }
 111                         continue;
 112                 }
 113                 err(1, "%s", in.name);
 114         }
 115 }
 116
 117 void
 118 pos_out(void)
 119 {
 120         struct mtop t_op;
 121         off_t cnt;
 122         ssize_t n;
 123
 124         /*
 125          * If not a tape, try seeking on the file.  Seeking on a pipe is
 126          * going to fail, but don't protect the user -- they shouldn't
 127          * have specified the seek operand.
 128          */
 129         if (out.flags & (ISSEEK | ISPIPE)) {
 130                 errno = 0;
 131                 if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
 132                     errno != 0)
 133                         err(1, "%s", out.name);
 134                 return;
 135         }
 136
 137         /* Don't try to read a really weird amount (like negative). */
 138         if (out.offset < 0)
 139                 errx(1, "%s: illegal offset", "oseek/seek");
 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) == -1)
 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 == -1)
 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                         n = write(out.fd, out.db, out.dbsz);
 171                         if (n == -1)
 172                                 err(1, "%s", out.name);
 173                         if ((size_t)n != out.dbsz)
 174                                 errx(1, "%s: write failure", out.name);
 175                 }
 176                 break;
 177         }
 178 }