archive_entry_linkify - archive_entry_linkresolver, archive_entry_linkresolver_new, archive_entry_linkresolver_set_strategy, hardlink resolver functions
#include <archive_entry.h> struct archive_entry_linkresolver * archive_entry_linkresolver_new(void); void archive_entry_linkresolver_set_strategy(- struct archive_entry_linkresolver *resolver, int format); void archive_entry_linkresolver_free(- struct archive_entry_linkresolver *resolver); void archive_entry_linkify(struct archive_entry_linkresolver *resolver, struct archive_entry **entry, struct archive_entry **sparse);
ARCHIVE_ENTRY_LINKIFY(3archive)
NAME
archive_entry_linkresolver, archive_entry_linkresolver_new,
archive_entry_linkresolver_set_strategy,
archive_entry_linkresolver_free, archive_entry_linkify - hardlink
resolver functions
LIBRARY
Streaming Archive Library (libarchive, -larchive)
SYNOPSIS
#include <archive_entry.h>
struct archive_entry_linkresolver *
archive_entry_linkresolver_new(void);
void
archive_entry_linkresolver_set_strategy(-
struct archive_entry_linkresolver *resolver, int format);
void
archive_entry_linkresolver_free(-
struct archive_entry_linkresolver *resolver);
void
archive_entry_linkify(struct archive_entry_linkresolver *resolver,
struct archive_entry **entry, struct archive_entry **sparse);
DESCRIPTION
Programs that want to create archives have to deal with hardlinks.
Hardlinks are handled in different ways by the archive formats. The
basic strategies are:
1. Ignore hardlinks and store the body for each reference (old
cpio, zip).
2. Store the body the first time an inode is seen (ustar,
pax).
3. Store the body the last time an inode is seen (new cpio).
The archive_entry_linkresolver functions help by providing a unified
interface and handling the complexity behind the scene.
The archive_entry_linkresolver functions assume that Vt archive_entry
instances have valid nlinks, inode and device values. The inode and
device value is used to match entries. The nlinks value is used to
determined if all references have been found and if the internal refer-
ences can be recycled.
The archive_entry_linkresolver_new() function allocates a new link
resolver. The instance can be freed using
archive_entry_linkresolver_free(). All deferred entries are flushed
and the internal storage is freed.
The archive_entry_linkresolver_set_strategy() function selects the
optimal hardlink strategy for the given format. The format code can be
obtained from archive_format(3). The function can be called more than
once, but it is recommended to flush all deferred entries first.
The archive_entry_linkify() function is the core of
archive_entry_linkresolver. The entry() argument points to the Vt ar-
chive_entry that should be written. Depending on the strategy one of
the following actions is taken:
1. For the simple archive formats *entry is left unmodified
and *sparse is set to NULL.
2. For tar like archive formats, *sparse is set to NULL. If
*entry is NULL, no action is taken. If the hardlink count
of *entry is larger than 1 and the file type is a regular
file or symbolic link, the internal list is searched for a
matching inode. If such an inode is found, the link count
is decremented and the file size of *entry is set to 0 to
notify that no body should be written. If no such inode is
found, a copy of the entry is added to the internal cache
with a link count reduced by one.
3. For new cpio like archive formats a value for *entry of
NULL is used to flush deferred entries. In that case
*entry is set to an arbitrary deferred entry and the entry
itself is removed from the internal list. If the internal
list is empty, *entry is set to NULL. In either case,
*sparse is set to NULL and the function returns. If the
hardlink count of *entry is one or the file type is a
directory or device, *sparse is set to NULL and no further
action is taken. Otherwise, the internal list is searched
for a matching inode. If such an inode is not found, the
entry is added to the internal list, both *entry and
*sparse are set to NULL and the function returns. If such
an inode is found, the link count is decremented. If it
remains larger than one, the existing entry on the internal
list is swapped with *entry after retaining the link count.
The existing entry is returned in *entry. If the link
count reached one, the new entry is also removed from the
internal list and returned in *sparse. Otherwise *sparse
is set to NULL.
The general usage is therefore:
1. For each new archive entry, call archive_entry_linkify().
2. Keep in mind that the entries returned may have a size of 0
now.
3. If *entry is not NULL, archive it.
4. If *sparse is not NULL, archive it.
5. After all entries have been written to disk, call
archive_entry_linkify() with *entry set to NULL and archive
the returned entry as long as it is not NULL.
RETURN VALUES
archive_entry_linkresolver_new() returns NULL on malloc(3) failures.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+---------------+--------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------+
|Availability | library/libarchive |
+---------------+--------------------+
|Stability | Uncommitted |
+---------------+--------------------+
SEE ALSO
archive_entry(3)
NOTES
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from
https://github.com/libarchive/libarchive/releases/down-
load/v3.6.1/libarchive-3.6.1.tar.gz.
Further information about this software can be found on the open source
community website at http://www.libarchive.org/.
February 2, 2012
ARCHIVE_ENTRY_LINKIFY(3archive)