summaryrefslogtreecommitdiffstats
path: root/lib/libarchive/archive_read_disk.3
blob: 290d3a1430b5c1323b981a81c4f431e0daa5a423 (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
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
.\" Copyright (c) 2003-2009 Tim Kientzle
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd March 10, 2009
.Dt ARCHIVE_READ_DISK 3
.Os
.Sh NAME
.Nm archive_read_disk_new ,
.Nm archive_read_disk_set_symlink_logical ,
.Nm archive_read_disk_set_symlink_physical ,
.Nm archive_read_disk_set_symlink_hybrid ,
.Nm archive_read_disk_entry_from_file ,
.Nm archive_read_disk_gname ,
.Nm archive_read_disk_uname ,
.Nm archive_read_disk_set_uname_lookup ,
.Nm archive_read_disk_set_gname_lookup ,
.Nm archive_read_disk_set_standard_lookup ,
.Nm archive_read_close ,
.Nm archive_read_free
.Nd functions for reading objects from disk
.Sh SYNOPSIS
.In archive.h
.Ft struct archive *
.Fn archive_read_disk_new "void"
.Ft int
.Fn archive_read_disk_set_symlink_logical "struct archive *"
.Ft int
.Fn archive_read_disk_set_symlink_physical "struct archive *"
.Ft int
.Fn archive_read_disk_set_symlink_hybrid "struct archive *"
.Ft int
.Fn archive_read_disk_gname "struct archive *" "gid_t"
.Ft int
.Fn archive_read_disk_uname "struct archive *" "uid_t"
.Ft int
.Fo archive_read_disk_set_gname_lookup
.Fa "struct archive *"
.Fa "void *"
.Fa "const char *(*lookup)(void *, gid_t)"
.Fa "void (*cleanup)(void *)"
.Fc
.Ft int
.Fo archive_read_disk_set_uname_lookup
.Fa "struct archive *"
.Fa "void *"
.Fa "const char *(*lookup)(void *, uid_t)"
.Fa "void (*cleanup)(void *)"
.Fc
.Ft int
.Fn archive_read_disk_set_standard_lookup "struct archive *"
.Ft int
.Fo archive_read_disk_entry_from_file
.Fa "struct archive *"
.Fa "struct archive_entry *"
.Fa "int fd"
.Fa "const struct stat *"
.Fc
.Ft int
.Fn archive_read_close "struct archive *"
.Ft int
.Fn archive_read_free "struct archive *"
.Sh DESCRIPTION
These functions provide an API for reading information about
objects on disk.
In particular, they provide an interface for populating
.Tn struct archive_entry
objects.
.Bl -tag -width indent
.It Fn archive_read_disk_new
Allocates and initializes a
.Tn struct archive
object suitable for reading object information from disk.
.It Xo
.Fn archive_read_disk_set_symlink_logical ,
.Fn archive_read_disk_set_symlink_physical ,
.Fn archive_read_disk_set_symlink_hybrid
.Xc
This sets the mode used for handling symbolic links.
The
.Dq logical
mode follows all symbolic links.
The
.Dq physical
mode does not follow any symbolic links.
The
.Dq hybrid
mode currently behaves identically to the
.Dq logical
mode.
.It Xo
.Fn archive_read_disk_gname ,
.Fn archive_read_disk_uname
.Xc
Returns a user or group name given a gid or uid value.
By default, these always return a NULL string.
.It Xo
.Fn archive_read_disk_set_gname_lookup ,
.Fn archive_read_disk_set_uname_lookup
.Xc
These allow you to override the functions used for
user and group name lookups.
You may also provide a
.Tn void *
pointer to a private data structure and a cleanup function for
that data.
The cleanup function will be invoked when the
.Tn struct archive
object is destroyed or when new lookup functions are registered.
.It Fn archive_read_disk_set_standard_lookup
This convenience function installs a standard set of user
and group name lookup functions.
These functions use
.Xr getpwid 3
and
.Xr getgrid 3
to convert ids to names, defaulting to NULL if the names cannot
be looked up.
These functions also implement a simple memory cache to reduce
the number of calls to
.Xr getpwid 3
and
.Xr getgrid 3 .
.It Fn archive_read_disk_entry_from_file
Populates a
.Tn struct archive_entry
object with information about a particular file.
The
.Tn archive_entry
object must have already been created with
.Xr archive_entry_new 3
and at least one of the source path or path fields must already be set.
(If both are set, the source path will be used.)
.Pp
Information is read from disk using the path name from the
.Tn struct archive_entry
object.
If a file descriptor is provided, some information will be obtained using
that file descriptor, on platforms that support the appropriate
system calls.
.Pp
If a pointer to a
.Tn struct stat
is provided, information from that structure will be used instead
of reading from the disk where appropriate.
This can provide performance benefits in scenarios where
.Tn struct stat
information has already been read from the disk as a side effect
of some other operation.
(For example, directory traversal libraries often provide this information.)
.Pp
Where necessary, user and group ids are converted to user and group names
using the currently registered lookup functions above.
This affects the file ownership fields and ACL values in the
.Tn struct archive_entry
object.
.It Fn archive_read_close
This currently does nothing.
.It Fn archive_read_free
Invokes
.Fn archive_read_close
if it was not invoked manually, then releases all resources.
.El
More information about the
.Va struct archive
object and the overall design of the library can be found in the
.Xr libarchive 3
overview.
.Sh EXAMPLE
The following illustrates basic usage of the library by
showing how to use it to copy an item on disk into an archive.
.Bd -literal -offset indent
void
file_to_archive(struct archive *a, const char *name)
{
  char buff[8192];
  size_t bytes_read;
  struct archive *ard;
  struct archive_entry *entry;
  int fd;

  ard = archive_read_disk_new();
  archive_read_disk_set_standard_lookup(ard);
  entry = archive_entry_new();
  fd = open(name, O_RDONLY);
  if (fd < 0)
     return;
  archive_entry_copy_sourcepath(entry, name);
  archive_read_disk_entry_from_file(ard, entry, fd, NULL);
  archive_write_header(a, entry);
  while ((bytes_read = read(fd, buff, sizeof(buff))) > 0)
    archive_write_data(a, buff, bytes_read);
  archive_write_finish_entry(a);
  archive_read_free(ard);
  archive_entry_free(entry);
}
.Ed
.Sh RETURN VALUES
Most functions return
.Cm ARCHIVE_OK
(zero) on success, or one of several negative
error codes for errors.
Specific error codes include:
.Cm ARCHIVE_RETRY
for operations that might succeed if retried,
.Cm ARCHIVE_WARN
for unusual conditions that do not prevent further operations, and
.Cm ARCHIVE_FATAL
for serious errors that make remaining operations impossible.
The
.Xr archive_errno 3
and
.Xr archive_error_string 3
functions can be used to retrieve an appropriate error code and a
textual error message.
(See
.Xr archive_util 3
for details.)
.Pp
.Fn archive_read_disk_new
returns a pointer to a newly-allocated
.Tn struct archive
object or NULL if the allocation failed for any reason.
.Pp
.Fn archive_read_disk_gname
and
.Fn archive_read_disk_uname
return
.Tn const char *
pointers to the textual name or NULL if the lookup failed for any reason.
The returned pointer points to internal storage that
may be reused on the next call to either of these functions;
callers should copy the string if they need to continue accessing it.
.Pp
.Sh SEE ALSO
.Xr archive_read 3 ,
.Xr archive_write 3 ,
.Xr archive_write_disk 3 ,
.Xr tar 1 ,
.Xr libarchive 3
.Sh HISTORY
The
.Nm libarchive
library first appeared in
.Fx 5.3 .
The
.Nm archive_read_disk
interface was added to
.Nm libarchive 2.6
and first appeared in
.Fx 8.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm libarchive
library was written by
.An Tim Kientzle Aq kientzle@FreeBSD.org .
.Sh BUGS
The
.Dq standard
user name and group name lookup functions are not the defaults because
.Xr getgrid 3
and
.Xr getpwid 3
are sometimes too large for particular applications.
The current design allows the application author to use a more
compact implementation when appropriate.
.Pp
The full list of metadata read from disk by
.Fn archive_read_disk_entry_from_file
is necessarily system-dependent.
.Pp
The
.Fn archive_read_disk_entry_from_file
function reads as much information as it can from disk.
Some method should be provided to limit this so that clients who
do not need ACLs, for instance, can avoid the extra work needed
to look up such information.
.Pp
This API should provide a set of methods for walking a directory tree.
That would make it a direct parallel of the
.Xr archive_read 3
API.
When such methods are implemented, the
.Dq hybrid
symbolic link mode will make sense.
OpenPOWER on IntegriCloud