summaryrefslogtreecommitdiffstats
path: root/Utilities/cmlibarchive/examples/untar.c
blob: f0d54c216001668a5e966fe32a557313a6760d36 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
/*
 * This file is in the public domain.
 * Use it as you wish.
 */

/*
 * This is a compact tar extraction program using libarchive whose
 * primary goal is small executable size.  Statically linked, it can
 * be very small, depending in large part on how cleanly factored your
 * system libraries are.  Note that this uses the standard libarchive,
 * without any special recompilation.  The only functional concession
 * is that this program uses the uid/gid from the archive instead of
 * doing uname/gname lookups.  (Add a call to
 * archive_write_disk_set_standard_lookup() to enable uname/gname
 * lookups, but be aware that this can add 500k or more to a static
 * executable, depending on the system libraries, since user/group
 * lookups frequently pull in password, YP/LDAP, networking, and DNS
 * resolver libraries.)
 *
 * To build:
 * $ gcc -static -Wall -o untar untar.c -larchive
 * $ strip untar
 *
 * NOTE: On some systems, you may need to add additional flags
 * to ensure that untar.c is compiled the same way as libarchive
 * was compiled.  In particular, Linux users will probably
 * have to add -D_FILE_OFFSET_BITS=64 to the command line above.
 *
 * For fun, statically compile the following simple hello.c program
 * using the same flags as for untar and compare the size:
 *
 * #include <stdio.h>
 * int main(int argc, char **argv) {
 *    printf("hello, world\n");
 *    return(0);
 * }
 *
 * You may be even more surprised by the compiled size of true.c listed here:
 *
 * int main(int argc, char **argv) {
 *    return (0);
 * }
 *
 * On a slightly customized FreeBSD 5 system that I used around
 * 2005, hello above compiled to 89k compared to untar of 69k.  So at
 * that time, libarchive's tar reader and extract-to-disk routines
 * compiled to less code than printf().
 *
 * On my FreeBSD development system today (August, 2009):
 *  hello: 195024 bytes
 *  true: 194912 bytes
 *  untar: 259924 bytes
 */

#include <sys/types.h>
__FBSDID("$FreeBSD$");

#include <sys/stat.h>

#include <archive.h>
#include <archive_entry.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static void errmsg(const char *);
static void extract(const char *filename, int do_extract, int flags);
static void fail(const char *, const char *, int);
static int  copy_data(struct archive *, struct archive *);
static void msg(const char *);
static void usage(void);
static void warn(const char *, const char *);

static int verbose = 0;

int
main(int argc, const char **argv)
{
    const char *filename = NULL;
    int compress, flags, mode, opt;

    (void)argc;
    mode = 'x';
    verbose = 0;
    compress = '\0';
    flags = ARCHIVE_EXTRACT_TIME;

    /* Among other sins, getopt(3) pulls in printf(3). */
    while (*++argv != NULL && **argv == '-') {
        const char *p = *argv + 1;

        while ((opt = *p++) != '\0') {
            switch (opt) {
            case 'f':
                if (*p != '\0')
                    filename = p;
                else
                    filename = *++argv;
                p += strlen(p);
                break;
            case 'p':
                flags |= ARCHIVE_EXTRACT_PERM;
                flags |= ARCHIVE_EXTRACT_ACL;
                flags |= ARCHIVE_EXTRACT_FFLAGS;
                break;
            case 't':
                mode = opt;
                break;
            case 'v':
                verbose++;
                break;
            case 'x':
                mode = opt;
                break;
            default:
                usage();
            }
        }
    }

    switch (mode) {
    case 't':
        extract(filename, 0, flags);
        break;
    case 'x':
        extract(filename, 1, flags);
        break;
    }

    return (0);
}


static void
extract(const char *filename, int do_extract, int flags)
{
    struct archive *a;
    struct archive *ext;
    struct archive_entry *entry;
    int r;

    a = archive_read_new();
    ext = archive_write_disk_new();
    archive_write_disk_set_options(ext, flags);
    /*
     * Note: archive_write_disk_set_standard_lookup() is useful
     * here, but it requires library routines that can add 500k or
     * more to a static executable.
     */
    archive_read_support_format_tar(a);
    /*
     * On my system, enabling other archive formats adds 20k-30k
     * each.  Enabling gzip decompression adds about 20k.
     * Enabling bzip2 is more expensive because the libbz2 library
     * isn't very well factored.
     */
    if (filename != NULL && strcmp(filename, "-") == 0)
        filename = NULL;
    if ((r = archive_read_open_file(a, filename, 10240)))
        fail("archive_read_open_file()",
            archive_error_string(a), r);
    for (;;) {
        r = archive_read_next_header(a, &entry);
        if (r == ARCHIVE_EOF)
            break;
        if (r != ARCHIVE_OK)
            fail("archive_read_next_header()",
                archive_error_string(a), 1);
        if (verbose && do_extract)
            msg("x ");
        if (verbose || !do_extract)
            msg(archive_entry_pathname(entry));
        if (do_extract) {
            r = archive_write_header(ext, entry);
            if (r != ARCHIVE_OK)
                warn("archive_write_header()",
                    archive_error_string(ext));
            else {
                copy_data(a, ext);
                r = archive_write_finish_entry(ext);
                if (r != ARCHIVE_OK)
                    fail("archive_write_finish_entry()",
                        archive_error_string(ext), 1);
            }

        }
        if (verbose || !do_extract)
            msg("\n");
    }
    archive_read_close(a);
    archive_read_finish(a);
    exit(0);
}

static int
copy_data(struct archive *ar, struct archive *aw)
{
    int r;
    const void *buff;
    size_t size;
    off_t offset;

    for (;;) {
        r = archive_read_data_block(ar, &buff, &size, &offset);
        if (r == ARCHIVE_EOF)
            return (ARCHIVE_OK);
        if (r != ARCHIVE_OK)
            return (r);
        r = archive_write_data_block(aw, buff, size, offset);
        if (r != ARCHIVE_OK) {
            warn("archive_write_data_block()",
                archive_error_string(aw));
            return (r);
        }
    }
}

/*
 * These reporting functions use low-level I/O; on some systems, this
 * is a significant code reduction.  Of course, on many server and
 * desktop operating systems, malloc() and even crt rely on printf(),
 * which in turn pulls in most of the rest of stdio, so this is not an
 * optimization at all there.  (If you're going to pay 100k or more
 * for printf() anyway, you may as well use it!)
 */
static void
msg(const char *m)
{
    write(1, m, strlen(m));
}

static void
errmsg(const char *m)
{
    write(2, m, strlen(m));
}

static void
warn(const char *f, const char *m)
{
    errmsg(f);
    errmsg(" failed: ");
    errmsg(m);
    errmsg("\n");
}

static void
fail(const char *f, const char *m, int r)
{
    warn(f, m);
    exit(r);
}

static void
usage(void)
{
    const char *m = "Usage: untar [-tvx] [-f file] [file]\n";
    errmsg(m);
    exit(1);
}