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28 .Dt ARCHIVE_READ_DISK 3
31 .Nm archive_read_disk_new ,
32 .Nm archive_read_disk_set_symlink_logical ,
33 .Nm archive_read_disk_set_symlink_physical ,
34 .Nm archive_read_disk_set_symlink_hybrid ,
35 .Nm archive_read_disk_entry_from_file ,
36 .Nm archive_read_disk_gname ,
37 .Nm archive_read_disk_uname ,
38 .Nm archive_read_disk_set_uname_lookup ,
39 .Nm archive_read_disk_set_gname_lookup ,
40 .Nm archive_read_disk_set_standard_lookup ,
41 .Nm archive_read_close ,
42 .Nm archive_read_finish ,
44 .Nd functions for reading objects from disk
46 Streaming Archive Library (libarchive, -larchive)
50 .Fn archive_read_disk_new "void"
52 .Fn archive_read_disk_set_symlink_logical "struct archive *"
54 .Fn archive_read_disk_set_symlink_physical "struct archive *"
56 .Fn archive_read_disk_set_symlink_hybrid "struct archive *"
58 .Fn archive_read_disk_gname "struct archive *" "gid_t"
60 .Fn archive_read_disk_uname "struct archive *" "uid_t"
62 .Fo archive_read_disk_set_gname_lookup
63 .Fa "struct archive *"
65 .Fa "const char *(*lookup)(void *, gid_t)"
66 .Fa "void (*cleanup)(void *)"
69 .Fo archive_read_disk_set_uname_lookup
70 .Fa "struct archive *"
72 .Fa "const char *(*lookup)(void *, uid_t)"
73 .Fa "void (*cleanup)(void *)"
76 .Fn archive_read_disk_set_standard_lookup "struct archive *"
78 .Fo archive_read_disk_entry_from_file
79 .Fa "struct archive *"
80 .Fa "struct archive_entry *"
82 .Fa "const struct stat *"
85 .Fn archive_read_close "struct archive *"
87 .Fn archive_read_finish "struct archive *"
89 .Fn archive_read_free "struct archive *"
91 These functions provide an API for reading information about
93 In particular, they provide an interface for populating
94 .Tn struct archive_entry
96 .Bl -tag -width indent
97 .It Fn archive_read_disk_new
98 Allocates and initializes a
100 object suitable for reading object information from disk.
102 .Fn archive_read_disk_set_symlink_logical ,
103 .Fn archive_read_disk_set_symlink_physical ,
104 .Fn archive_read_disk_set_symlink_hybrid
106 This sets the mode used for handling symbolic links.
109 mode follows all symbolic links.
112 mode does not follow any symbolic links.
115 mode currently behaves identically to the
119 .Fn archive_read_disk_gname ,
120 .Fn archive_read_disk_uname
122 Returns a user or group name given a gid or uid value.
123 By default, these always return a NULL string.
125 .Fn archive_read_disk_set_gname_lookup ,
126 .Fn archive_read_disk_set_uname_lookup
128 These allow you to override the functions used for
129 user and group name lookups.
130 You may also provide a
132 pointer to a private data structure and a cleanup function for
134 The cleanup function will be invoked when the
136 object is destroyed or when new lookup functions are registered.
137 .It Fn archive_read_disk_set_standard_lookup
138 This convenience function installs a standard set of user
139 and group name lookup functions.
144 to convert ids to names, defaulting to NULL if the names cannot
146 These functions also implement a simple memory cache to reduce
147 the number of calls to
151 .It Fn archive_read_disk_entry_from_file
153 .Tn struct archive_entry
154 object with information about a particular file.
157 object must have already been created with
158 .Xr archive_entry_new 3
159 and at least one of the source path or path fields must already be set.
160 (If both are set, the source path will be used.)
162 Information is read from disk using the path name from the
163 .Tn struct archive_entry
165 If a file descriptor is provided, some information will be obtained using
166 that file descriptor, on platforms that support the appropriate
171 is provided, information from that structure will be used instead
172 of reading from the disk where appropriate.
173 This can provide performance benefits in scenarios where
175 information has already been read from the disk as a side effect
176 of some other operation.
177 (For example, directory traversal libraries often provide this information.)
179 Where necessary, user and group ids are converted to user and group names
180 using the currently registered lookup functions above.
181 This affects the file ownership fields and ACL values in the
182 .Tn struct archive_entry
184 .It Fn archive_read_close
186 .Tn archive_read_disk
188 .It Fn archive_read_finish
189 This is a deprecated synonym for
190 .Fn archive_read_free .
191 .It Fn archive_read_free
193 .Fn archive_read_close
194 if it was not invoked manually, then releases all resources.
196 More information about the
198 object and the overall design of the library can be found in the
202 The following illustrates basic usage of the library by
203 showing how to use it to copy an item on disk into an archive.
204 .Bd -literal -offset indent
206 file_to_archive(struct archive *a, const char *name)
211 struct archive_entry *entry;
214 ard = archive_read_disk_new();
215 archive_read_disk_set_standard_lookup(ard);
216 entry = archive_entry_new();
217 fd = open(name, O_RDONLY);
220 archive_entry_copy_pathname(entry, name);
221 archive_read_disk_entry_from_file(ard, entry, fd, NULL);
222 archive_write_header(a, entry);
223 while ((bytes_read = read(fd, buff, sizeof(buff))) > 0)
224 archive_write_data(a, buff, bytes_read);
225 archive_write_finish_entry(a);
226 archive_read_free(ard);
227 archive_entry_free(entry);
231 Most functions return
233 (zero) on success, or one of several negative
234 error codes for errors.
235 Specific error codes include:
237 for operations that might succeed if retried,
239 for unusual conditions that do not prevent further operations, and
241 for serious errors that make remaining operations impossible.
243 .Fn archive_read_disk_new
244 returns a pointer to a newly-allocated
246 object or NULL if the allocation failed for any reason.
248 .Fn archive_read_disk_gname
250 .Fn archive_read_disk_uname
253 pointers to the textual name or NULL if the lookup failed for any reason.
254 The returned pointer points to internal storage that
255 may be reused on the next call to either of these functions;
256 callers should copy the string if they need to continue accessing it.
259 Detailed error codes and textual descriptions are available from the
262 .Fn archive_error_string
268 .Xr archive_write 3 ,
269 .Xr archive_write_disk 3 ,
275 library first appeared in
278 .Nm archive_read_disk
279 interface was added to
281 and first appeared in
287 library was written by
288 .An Tim Kientzle Aq kientzle@FreeBSD.org .
292 user name and group name lookup functions are not the defaults because
296 are sometimes too large for particular applications.
297 The current design allows the application author to use a more
298 compact implementation when appropriate.
300 The full list of metadata read from disk by
301 .Fn archive_read_disk_entry_from_file
302 is necessarily system-dependent.
305 .Fn archive_read_disk_entry_from_file
306 function reads as much information as it can from disk.
307 Some method should be provided to limit this so that clients who
308 do not need ACLs, for instance, can avoid the extra work needed
309 to look up such information.
311 This API should provide a set of methods for walking a directory tree.
312 That would make it a direct parallel of the
315 When such methods are implemented, the
317 symbolic link mode will make sense.