file_cmds/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 #include <sys/cdefs.h>
  39 #ifndef lint
  40 #if 0
  41 static char sccsid[] = "@(#)position.c  8.3 (Berkeley) 4/2/94";
  42 #endif
  43 __used static const char rcsid[] =
  44   "$FreeBSD: src/bin/dd/position.c,v 1.20 2002/02/02 06:24:12 imp Exp $";
  45 #endif /* not lint */
  46
  47 #include <sys/types.h>
  48
  49 #ifdef __APPLE__
  50 #include <sys/ioctl.h>
  51 #endif
  52
  53 #include <err.h>
  54 #include <errno.h>
  55 #include <unistd.h>
  56
  57 #include "dd.h"
  58 #include "extern.h"
  59
  60 /*
  61  * Position input/output data streams before starting the copy.  Device type
  62  * dependent.  Seekable devices use lseek, and the rest position by reading.
  63  * Seeking past the end of file can cause null blocks to be written to the
  64  * output.
  65  */
  66 void
  67 pos_in(void)
  68 {
  69         off_t cnt;
  70         int warned;
  71         ssize_t nr;
  72         size_t bcnt;
  73
  74         /* If known to be seekable, try to seek on it. */
  75         if (in.flags & ISSEEK) {
  76                 errno = 0;
  77                 if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
  78                     errno != 0)
  79                         err(1, "%s", in.name);
  80                 return;
  81         }
  82
  83         /* Don't try to read a really weird amount (like negative). */
  84         if (in.offset < 0)
  85                 errx(1, "%s: illegal offset", "iseek/skip");
  86
  87         /*
  88          * Read the data.  If a pipe, read until satisfy the number of bytes
  89          * being skipped.  No differentiation for reading complete and partial
  90          * blocks for other devices.
  91          */
  92         for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
  93                 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
  94                         if (in.flags & ISPIPE) {
  95                                 if (!(bcnt -= nr)) {
  96                                         bcnt = in.dbsz;
  97                                         --cnt;
  98                                 }
  99                         } else
 100                                 --cnt;
 101                         continue;
 102                 }
 103
 104                 if (nr == 0) {
 105                         if (files_cnt > 1) {
 106                                 --files_cnt;
 107                                 continue;
 108                         }
 109                         errx(1, "skip reached end of input");
 110                 }
 111
 112                 /*
 113                  * Input error -- either EOF with no more files, or I/O error.
 114                  * If noerror not set die.  POSIX requires that the warning
 115                  * message be followed by an I/O display.
 116                  */
 117                 if (ddflags & C_NOERROR) {
 118                         if (!warned) {
 119                                 warn("%s", in.name);
 120                                 warned = 1;
 121                                 summary();
 122                         }
 123                         continue;
 124                 }
 125                 err(1, "%s", in.name);
 126         }
 127 }
 128
 129 void
 130 pos_out(void)
 131 {
 132         off_t cnt;
 133         ssize_t n;
 134
 135         /*
 136          * If not a tape, try seeking on the file.  Seeking on a pipe is
 137          * going to fail, but don't protect the user -- they shouldn't
 138          * have specified the seek operand.
 139          */
 140         if (out.flags & (ISSEEK | ISPIPE)) {
 141                 errno = 0;
 142                 if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
 143                     errno != 0)
 144                         err(1, "%s", out.name);
 145                 return;
 146         }
 147
 148         /* Don't try to read a really weird amount (like negative). */
 149         if (out.offset < 0)
 150                 errx(1, "%s: illegal offset", "oseek/seek");
 151
 152         /* Read it. */
 153         for (cnt = 0; cnt < out.offset; ++cnt) {
 154                 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
 155                         continue;
 156
 157                 if (n == -1)
 158                         err(1, "%s", out.name);
 159
 160                 while (cnt++ < out.offset) {
 161                         n = write(out.fd, out.db, out.dbsz);
 162                         if (n == -1)
 163                                 err(1, "%s", out.name);
 164                         if ((size_t)n != out.dbsz)
 165                                 errx(1, "%s: write failure", out.name);
 166                 }
 167                 break;
 168         }
 169 }