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1 | /*- |
2 | * Copyright (c) 1991 The Regents of the University of California. | |
3 | * 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. | |
7 | * | |
8 | * %sccs.include.redist.c% | |
9 | */ | |
10 | ||
11 | #ifndef lint | |
12 | static char sccsid[] = "@(#)position.c 5.1 (Berkeley) %G%"; | |
13 | #endif /* not lint */ | |
14 | ||
15 | #include <sys/types.h> | |
16 | #include <sys/stat.h> | |
17 | #include <sys/ioctl.h> | |
18 | #include <sys/mtio.h> | |
19 | #include <errno.h> | |
20 | #include <unistd.h> | |
21 | #include <string.h> | |
22 | #include "dd.h" | |
23 | #include "extern.h" | |
24 | ||
25 | /* | |
26 | * Position input/output data streams before starting the copy. Device type | |
27 | * dependent. Seekable devices use lseek, and the rest position by reading. | |
28 | * Seeking past the end of file can cause null blocks to be written to the | |
29 | * output. | |
30 | */ | |
31 | void | |
32 | pos_in() | |
33 | { | |
34 | register int bcnt, cnt, nr, warned; | |
35 | ||
36 | /* If not a character, pipe or tape device, try to seek on it. */ | |
37 | if (!(in.flags & (ISCHR|ISPIPE|ISTAPE))) { | |
38 | if (lseek(in.fd, (off_t)(in.offset * in.dbsz), SEEK_CUR) == -1) | |
39 | err("%s: %s", in.name, strerror(errno)); | |
40 | return; | |
41 | } | |
42 | ||
43 | /* | |
44 | * Read the data. If a pipe, read until satisfy the number of bytes | |
45 | * being skipped. No differentiation for reading complete and partial | |
46 | * blocks for other devices. | |
47 | */ | |
48 | for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) { | |
49 | if ((nr = read(in.fd, in.db, bcnt)) > 0) | |
50 | if (in.flags & ISPIPE) { | |
51 | if (!(bcnt -= nr)) { | |
52 | bcnt = in.dbsz; | |
53 | --cnt; | |
54 | } | |
55 | continue; | |
56 | } else | |
57 | --cnt; | |
58 | ||
59 | if (nr == 0) { | |
60 | if (files_cnt > 1) { | |
61 | --files_cnt; | |
62 | continue; | |
63 | } | |
64 | err("skip reached end of input"); | |
65 | } | |
66 | ||
67 | /* | |
68 | * Input error -- either EOF with no more files, or I/O error. | |
69 | * If noerror not set die. POSIX requires that the warning | |
70 | * message be followed by an I/O display. | |
71 | */ | |
72 | if (ddflags & C_NOERROR) { | |
73 | if (!warned) { | |
74 | warn("%s: %s", in.name, strerror(errno)); | |
75 | warned = 1; | |
76 | summary(0); | |
77 | } | |
78 | continue; | |
79 | } | |
80 | err("%s: %s", in.name, strerror(errno)); | |
81 | } | |
82 | } | |
83 | ||
84 | void | |
85 | pos_out() | |
86 | { | |
87 | register int cnt, n; | |
88 | struct mtop t_op; | |
89 | ||
90 | /* | |
91 | * If not a tape, try seeking on the file. Seeking on a pipe is | |
92 | * going to fail, but don't protect the user -- they shouldn't | |
93 | * have specified the seek operand. | |
94 | */ | |
95 | if (!(out.flags & ISTAPE)) { | |
96 | if (lseek(out.fd, | |
97 | (off_t)out.offset * out.dbsz, SEEK_SET) == -1) | |
98 | err("%s: %s", out.name, strerror(errno)); | |
99 | return; | |
100 | } | |
101 | ||
102 | /* If no read access, try using mtio. */ | |
103 | if (out.flags & NOREAD) { | |
104 | t_op.mt_op = MTFSR; | |
105 | t_op.mt_count = out.offset; | |
106 | ||
107 | if (ioctl(out.fd, MTIOCTOP, &t_op) < 0) | |
108 | err("%s: %s", out.name, strerror(errno)); | |
109 | return; | |
110 | } | |
111 | ||
112 | /* Read it. */ | |
113 | for (cnt = 0; cnt < out.offset; ++cnt) { | |
114 | if ((n = read(out.fd, out.db, out.dbsz)) > 0) | |
115 | continue; | |
116 | ||
117 | if (n < 0) | |
118 | err("%s: %s", out.name, strerror(errno)); | |
119 | ||
120 | /* | |
121 | * If reach EOF, fill with NUL characters; first, back up over | |
122 | * the EOF mark. Note, cnt has not yet been incremented, so | |
123 | * the EOF read does not count as a seek'd block. | |
124 | */ | |
125 | t_op.mt_op = MTBSR; | |
126 | t_op.mt_count = 1; | |
127 | if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) | |
128 | err("%s: %s", out.name, strerror(errno)); | |
129 | ||
130 | while (cnt++ < out.offset) | |
131 | if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz) | |
132 | err("%s: %s", out.name, strerror(errno)); | |
133 | break; | |
134 | } | |
135 | } |