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.\"
.IX Title "Hierarchy 3"
.TH Hierarchy 3 2023-07-25 "perl v5.38.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH NAME
Data::Hierarchy \- Handle data in a hierarchical structure
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 4
\&    my $tree = Data::Hierarchy\->new();
\&    $tree\->store (\*(Aq/\*(Aq, {access => \*(Aqall\*(Aq});
\&    $tree\->store (\*(Aq/private\*(Aq, {access => \*(Aqauth\*(Aq,
\&                               \*(Aq.note\*(Aq => \*(Aqthis is private});
\&
\&    $info = $tree\->get (\*(Aq/private/somewhere/deep\*(Aq);
\&
\&    # return actual data points in list context
\&    ($info, @fromwhere) = $tree\->get (\*(Aq/private/somewhere/deep\*(Aq);
\&
\&    my @items = $tree\->find (\*(Aq/\*(Aq, {access => qr/.*/});
\&
\&    # override all children
\&    $tree\->store (\*(Aq/\*(Aq, {\*(Aq.note\*(Aq => undef}, {override_sticky_descendents => 1});
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Data::Hierarchy provides a simple interface for manipulating
inheritable data attached to a hierarchical environment (like
a filesystem).
.PP
One use of Data::Hierarchy is to allow an application to annotate
paths in a real filesystem in a single compact data
structure. However, the hierarchy does not actually need to correspond
to an actual filesystem.
.PP
Paths in a hierarchy are referred to in a Unix-like syntax; \f(CW"/"\fR is
the root "directory". (You can specify a different separator character
than the slash when you construct a Data::Hierarchy object.)  With the
exception of the root path, paths should never contain trailing
slashes. You can associate properties, which are arbitrary name/value
pairs, with any path.  (Properties cannot contain the undefined value.)
By default, properties are inherited by child
paths: thus, if you store some data at \f(CW\*(C`/some/path\*(C'\fR:
.PP
.Vb 1
\&    $tree\->store(\*(Aq/some/path\*(Aq, {color => \*(Aqred\*(Aq});
.Ve
.PP
you can fetch it again at a \f(CW\*(C`/some/path/below/that\*(C'\fR:
.PP
.Vb 2
\&    print $tree\->get(\*(Aq/some/path/below/that\*(Aq)\->{\*(Aqcolor\*(Aq};
\&    # prints red
.Ve
.PP
On the other hand, properties whose names begin with dots are
uninherited, or "sticky":
.PP
.Vb 3
\&    $tree\->store(\*(Aq/some/path\*(Aq, {\*(Aq.color\*(Aq => \*(Aqblue\*(Aq});
\&    print $tree\->get(\*(Aq/some/path\*(Aq)\->{\*(Aq.color\*(Aq};            # prints blue
\&    print $tree\->get(\*(Aq/some/path/below/that\*(Aq)\->{\*(Aq.color\*(Aq}; # undefined
.Ve
.PP
Note that you do not need to (and in fact, cannot) explicitly add
"files" or "directories" to the hierarchy; you simply add and delete
properties to paths.
.SH CONSTRUCTOR
.IX Header "CONSTRUCTOR"
Creates a new hierarchy object.  Takes the following options:
.IP sep 4
.IX Item "sep"
The string used as a separator between path levels. Defaults to '/'.
.SH METHODS
.IX Header "METHODS"
.SS "Instance Methods"
.IX Subsection "Instance Methods"
.ie n .IP """store $path, $properties, {%options}""" 4
.el .IP "\f(CWstore $path, $properties, {%options}\fR" 4
.IX Item "store $path, $properties, {%options}"
Given a path and a hash reference of properties, stores the properties
at the path.
.Sp
Unless the \f(CW\*(C`override_descendents\*(C'\fR option is given with a false value,
it eliminates any non-sticky property in a descendent of \f(CW$path\fR with
the same name.
.Sp
If the \f(CW\*(C`override_sticky_descendents\*(C'\fR option is given with a true
value, it eliminates any sticky property in a descendent of \f(CW$path\fR
with the same name.  override it.
.Sp
A value of undef removes that value; note, though, that
if an ancestor of \f(CW$path\fR defines that property, the ancestor's value
will be inherited there; that is, with:
.Sp
.Vb 4
\&    $t\->store(\*(Aq/a\*(Aq,   {k => \*(Aqtop\*(Aq});
\&    $t\->store(\*(Aq/a/b\*(Aq, {k => \*(Aqbottom\*(Aq});
\&    $t\->store(\*(Aq/a/b\*(Aq, {k => undef});
\&    print $t\->get(\*(Aq/a/b\*(Aq)\->{\*(Aqk\*(Aq};
.Ve
.Sp
it will print 'top'.
.ie n .IP """get $path, [$dont_clone]""" 4
.el .IP "\f(CWget $path, [$dont_clone]\fR" 4
.IX Item "get $path, [$dont_clone]"
Given a path, looks up all of the properteies (sticky and not) and
returns them in a hash reference.  The values are clones, unless you
pass a true value for \f(CW$dont_clone\fR.
.Sp
If called in list context, returns that hash reference followed by all
of the ancestral paths of \f(CW$path\fR which contain non-sticky properties
(possibly including itself).
.ie n .IP """find $path, $property_regexps""" 4
.el .IP "\f(CWfind $path, $property_regexps\fR" 4
.IX Item "find $path, $property_regexps"
Given a path and a hash reference of name/regular expression pairs,
returns a list of all paths which are descendents of \f(CW$path\fR
(including itself) and define \fBat that path itself\fR (not inherited)
all of the properties in the hash with values matching the given
regular expressions.  (You may want to use \f(CW\*(C`qr/.*/\*(C'\fR to merely see if
it has any value defined there.)  Properties can be sticky or not.
.ie n .IP """merge $other_hierarchy, $path""" 4
.el .IP "\f(CWmerge $other_hierarchy, $path\fR" 4
.IX Item "merge $other_hierarchy, $path"
Given a second Data::Hierarchy object and a path, copies all the
properties from the other object at \f(CW$path\fR or below into the
corresponding paths in the object this method is invoked on.  All
properties from the object this is invoked on at \f(CW$path\fR or below are
erased first.
.ie n .IP """to_relative $base_path""" 4
.el .IP "\f(CWto_relative $base_path\fR" 4
.IX Item "to_relative $base_path"
Given a path which \fBevery\fR element of the hierarchy must be contained
in, returns a special Data::Hierarchy::Relative object which
represents the hierarchy relative that path. The \fBonly\fR thing you can
do with a Data::Hierarchy::Relative object is call
\&\f(CWto_absolute($new_base_path)\fR on it, which returns a new
Data::Hierarchy object at that base path. For example, if
everything in the hierarchy is rooted at \f(CW\*(C`/home/super_project\*(C'\fR and it
needs to be moved to \f(CW\*(C`/home/awesome_project\*(C'\fR, you can do
.Sp
.Vb 1
\&    $hierarchy = $hierarchy\->to_relative(\*(Aq/home/super_project\*(Aq)\->to_absolute(\*(Aq/home/awesome_project\*(Aq);
.Ve
.Sp
(Data::Hierarchy::Relative objects may be a more convenient
serialization format than Data::Hierarchy objects, if they are
tracking the state of some relocatable resource.)
.SH AUTHORS
.IX Header "AUTHORS"
Chia-liang Kao <clkao@clkao.org>
David Glasser <glasser@mit.edu>
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2003\-2006 by Chia-liang Kao <clkao@clkao.org>.
.PP
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
.PP
See <http://www.perl.com/perl/misc/Artistic.html>