xref: /freebsd/bin/dd/position.c (revision 3642298923e528d795e3a30ec165d2b469e28b40)
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  * 4. 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 
34 #ifndef lint
35 #if 0
36 static char sccsid[] = "@(#)position.c	8.3 (Berkeley) 4/2/94";
37 #endif
38 #endif /* not lint */
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
41 
42 #include <sys/types.h>
43 #include <sys/mtio.h>
44 
45 #include <err.h>
46 #include <errno.h>
47 #include <inttypes.h>
48 #include <unistd.h>
49 
50 #include "dd.h"
51 #include "extern.h"
52 
53 /*
54  * Position input/output data streams before starting the copy.  Device type
55  * dependent.  Seekable devices use lseek, and the rest position by reading.
56  * Seeking past the end of file can cause null blocks to be written to the
57  * output.
58  */
59 void
60 pos_in(void)
61 {
62 	off_t cnt;
63 	int warned;
64 	ssize_t nr;
65 	size_t bcnt;
66 
67 	/* If known to be seekable, try to seek on it. */
68 	if (in.flags & ISSEEK) {
69 		errno = 0;
70 		if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
71 		    errno != 0)
72 			err(1, "%s", in.name);
73 		return;
74 	}
75 
76 	/* Don't try to read a really weird amount (like negative). */
77 	if (in.offset < 0)
78 		errx(1, "%s: illegal offset", "iseek/skip");
79 
80 	/*
81 	 * Read the data.  If a pipe, read until satisfy the number of bytes
82 	 * being skipped.  No differentiation for reading complete and partial
83 	 * blocks for other devices.
84 	 */
85 	for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
86 		if ((nr = read(in.fd, in.db, bcnt)) > 0) {
87 			if (in.flags & ISPIPE) {
88 				if (!(bcnt -= nr)) {
89 					bcnt = in.dbsz;
90 					--cnt;
91 				}
92 			} else
93 				--cnt;
94 			continue;
95 		}
96 
97 		if (nr == 0) {
98 			if (files_cnt > 1) {
99 				--files_cnt;
100 				continue;
101 			}
102 			errx(1, "skip reached end of input");
103 		}
104 
105 		/*
106 		 * Input error -- either EOF with no more files, or I/O error.
107 		 * If noerror not set die.  POSIX requires that the warning
108 		 * message be followed by an I/O display.
109 		 */
110 		if (ddflags & C_NOERROR) {
111 			if (!warned) {
112 				warn("%s", in.name);
113 				warned = 1;
114 				summary();
115 			}
116 			continue;
117 		}
118 		err(1, "%s", in.name);
119 	}
120 }
121 
122 void
123 pos_out(void)
124 {
125 	struct mtop t_op;
126 	off_t cnt;
127 	ssize_t 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 & (ISSEEK | ISPIPE)) {
135 		errno = 0;
136 		if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
137 		    errno != 0)
138 			err(1, "%s", out.name);
139 		return;
140 	}
141 
142 	/* Don't try to read a really weird amount (like negative). */
143 	if (out.offset < 0)
144 		errx(1, "%s: illegal offset", "oseek/seek");
145 
146 	/* If no read access, try using mtio. */
147 	if (out.flags & NOREAD) {
148 		t_op.mt_op = MTFSR;
149 		t_op.mt_count = out.offset;
150 
151 		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
152 			err(1, "%s", out.name);
153 		return;
154 	}
155 
156 	/* Read it. */
157 	for (cnt = 0; cnt < out.offset; ++cnt) {
158 		if ((n = read(out.fd, out.db, out.dbsz)) > 0)
159 			continue;
160 
161 		if (n == -1)
162 			err(1, "%s", out.name);
163 
164 		/*
165 		 * If reach EOF, fill with NUL characters; first, back up over
166 		 * the EOF mark.  Note, cnt has not yet been incremented, so
167 		 * the EOF read does not count as a seek'd block.
168 		 */
169 		t_op.mt_op = MTBSR;
170 		t_op.mt_count = 1;
171 		if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
172 			err(1, "%s", out.name);
173 
174 		while (cnt++ < out.offset) {
175 			n = write(out.fd, out.db, out.dbsz);
176 			if (n == -1)
177 				err(1, "%s", out.name);
178 			if ((size_t)n != out.dbsz)
179 				errx(1, "%s: write failure", out.name);
180 		}
181 		break;
182 	}
183 }
184