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
  38 #ifndef lint
  39 #if 0
  40 static char sccsid[] = "@(#)position.c  8.3 (Berkeley) 4/2/94";
  41 #endif
  42 static const char rcsid[] =
  43   "$FreeBSD: src/bin/dd/position.c,v 1.20 2002/02/02 06:24:12 imp Exp $";
  44 #endif /* not lint */
  45
  46 #include <sys/types.h>
  47
  48 #ifdef __APPLE__
  49 #include <sys/ioctl.h>
  50 #endif
  51
  52 #include <err.h>
  53 #include <errno.h>
  54 #include <unistd.h>
  55
  56 #include "dd.h"
  57 #include "extern.h"
  58
  59 /*
  60  * Position input/output data streams before starting the copy.  Device type
  61  * dependent.  Seekable devices use lseek, and the rest position by reading.
  62  * Seeking past the end of file can cause null blocks to be written to the
  63  * output.
  64  */
  65 void
  66 pos_in(void)
  67 {
  68         off_t cnt;
  69         int warned;
  70         ssize_t nr;
  71         size_t bcnt;
  72
  73         /* If known to be seekable, try to seek on it. */
  74         if (in.flags & ISSEEK) {
  75                 errno = 0;
  76                 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
  77                     errno != 0)
  78                         err(1, "%s", in.name);
  79                 return;
  80         }
  81
  82         /* Don't try to read a really weird amount (like negative). */
  83         if (in.offset < 0)
  84                 errx(1, "%s: illegal offset", "iseek/skip");
  85
  86         /*
  87          * Read the data.  If a pipe, read until satisfy the number of bytes
  88          * being skipped.  No differentiation for reading complete and partial
  89          * blocks for other devices.
  90          */
  91         for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
  92                 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
  93                         if (in.flags & ISPIPE) {
  94                                 if (!(bcnt -= nr)) {
  95                                         bcnt = in.dbsz;
  96                                         --cnt;
  97                                 }
  98                         } else
  99                                 --cnt;
 100                         continue;
 101                 }
 102
 103                 if (nr == 0) {
 104                         if (files_cnt > 1) {
 105                                 --files_cnt;
 106                                 continue;
 107                         }
 108                         errx(1, "skip reached end of input");
 109                 }
 110
 111                 /*
 112                  * Input error -- either EOF with no more files, or I/O error.
 113                  * If noerror not set die.  POSIX requires that the warning
 114                  * message be followed by an I/O display.
 115                  */
 116                 if (ddflags & C_NOERROR) {
 117                         if (!warned) {
 118                                 warn("%s", in.name);
 119                                 warned = 1;
 120                                 summary();
 121                         }
 122                         continue;
 123                 }
 124                 err(1, "%s", in.name);
 125         }
 126 }
 127
 128 void
 129 pos_out(void)
 130 {
 131         off_t cnt;
 132         ssize_t n;
 133
 134         /*
 135          * If not a tape, try seeking on the file.  Seeking on a pipe is
 136          * going to fail, but don't protect the user -- they shouldn't
 137          * have specified the seek operand.
 138          */
 139         if (out.flags & (ISSEEK | ISPIPE)) {
 140                 errno = 0;
 141                 if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
 142                     errno != 0)
 143                         err(1, "%s", out.name);
 144                 return;
 145         }
 146
 147         /* Don't try to read a really weird amount (like negative). */
 148         if (out.offset < 0)
 149                 errx(1, "%s: illegal offset", "oseek/seek");
 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                 while (cnt++ < out.offset) {
 160                         n = write(out.fd, out.db, out.dbsz);
 161                         if (n == -1)
 162                                 err(1, "%s", out.name);
 163                         if ((size_t)n != out.dbsz)
 164                                 errx(1, "%s: write failure", out.name);
 165                 }
 166                 break;
 167         }
 168 }