ARCHIVE_ENTRY_LINKIFY(3) | Library Functions Manual | ARCHIVE_ENTRY_LINKIFY(3) |
archive_entry_linkresolver
,
archive_entry_linkresolver_new
,
archive_entry_linkresolver_set_strategy
,
archive_entry_linkresolver_free
,
archive_entry_linkify
—
hardlink resolver functions
Streaming Archive Library (libarchive, -larchive)
#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);
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:
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 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 references 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 archive_entry that should be
written. Depending on the strategy one of the following actions is
taken:
NULL
.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.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:
archive_entry_linkify
().NULL
,
archive it.NULL
,
archive it.archive_entry_linkify
() with
*entry set to NULL
and
archive the returned entry as long as it is not
NULL
.archive_entry_linkresolver_new
() returns
NULL
on
malloc(3) failures.
February 2, 2012 | macOS 14.6 |