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.TH ARCHIVE_ENTRY_LINKIFY 3 "February 20, 2010" ""
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\fB\%archive_entry_linkresolver\fP,
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\fB\%archive_entry_linkresolver_new\fP,
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\fB\%archive_entry_linkresolver_set_strategy\fP,
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\fB\%archive_entry_linkresolver_free\fP,
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\fB\%archive_entry_linkify\fP
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\- hardlink resolver functions
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\fB#include <archive_entry.h>\fP
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\fIstruct archive_entry_linkresolver *\fP
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\fB\%archive_entry_linkresolver_new\fP(\fI\%void\fP);
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\fB\%archive_entry_linkresolver_set_strategy\fP(\fI\%struct\ archive_entry_linkresolver\ *resolver\fP, \fI\%int\ format\fP);
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\fB\%archive_entry_linkresolver_free\fP(\fI\%struct\ archive_entry_linkresolver\ *resolver\fP);
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\fB\%archive_entry_linkify\fP(\fI\%struct\ archive_entry_linkresolver\ *resolver\fP, \fI\%struct\ archive_entry\ **entry\fP, \fI\%struct\ archive_entry\ **sparse\fP);
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Programs that want to create archives have to deal with hardlinks.
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Hardlinks are handled in different ways by the archive formats.
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The basic strategies are:
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Ignore hardlinks and store the body for each reference (old cpio, zip).
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Store the body the first time an inode is seen (ustar, pax).
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Store the body the last time an inode is seen (new cpio).
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\fB\%archive_entry_linkresolver\fP
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functions help by providing a unified interface and handling the complexity
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\fB\%archive_entry_linkresolver\fP
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instances have valid nlinks, inode and device values.
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The inode and device value is used to match entries.
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The nlinks value is used to determined if all references have been found and
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if the internal references can be recycled.
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\fB\%archive_entry_linkresolver_new\fP()
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function allocates a new link resolver.
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The instance can be freed using
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\fB\%archive_entry_linkresolver_free\fP().
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All deferred entries are flushed and the internal storage is freed.
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\fB\%archive_entry_linkresolver_set_strategy\fP()
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function selects the optimal hardlink strategy for the given format.
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The format code can be obtained from
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\fBarchive_format\fP(3).
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The function can be called more than once, but it is recommended to
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flush all deferred entries first.
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\fB\%archive_entry_linkify\fP()
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function is the core of
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\fB\%archive_entry_linkresolver\fP.
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argument points to the
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that should be written.
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Depending on the strategy one of the following actions is taken:
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For the simple archive formats
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is left unmodified and
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For tar like archive formats,
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If the hardlink count of
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is larger than 1 and the file type is a regular file or symbolic link,
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the internal list is searched for a matching inode.
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If such an inode is found, the link count is decremented and the file size
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is set to 0 to notify that no body should be written.
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If no such inode is found, a copy of the entry is added to the internal cache
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with a link count reduced by one.
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For new cpio like archive formats a value for
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is used to flush deferred entries.
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is set to an arbitrary deferred entry and the entry itself is removed from the
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If the internal list is empty,
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and the function returns.
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If the hardlink count of
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is one or the file type is a directory or device,
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and no further action is taken.
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Otherwise, the internal list is searched for a matching inode.
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If such an inode is not found, the entry is added to the internal list,
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and the function returns.
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If such an inode is found, the link count is decremented.
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If it remains larger than one, the existing entry on the internal list
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after retaining the link count.
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The existing entry is returned in
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If the link count reached one, the new entry is also removed from the
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internal list and returned in
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The general usage is therefore:
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For each new archive entry, call
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\fB\%archive_entry_linkify\fP().
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Keep in mind that the entries returned may have a size of 0 now.
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After all entries have been written to disk, call
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\fB\%archive_entry_linkify\fP()
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and archive the returned entry as long as it is not
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\fB\%archive_entry_linkresolver_new\fP()
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\fBarchive_entry\fP(3)
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doc/man/archive_entry_linkify.3
