Provided by: libcgi-expand-perl_2.05-6_all bug

NAME

       CGI::Expand - convert flat hash to nested data using TT2's dot convention

SYNOPSIS

           use CGI::Expand ();
           use CGI; # or Apache::Request, etc.

           $args = CGI::Expand->expand_cgi( CGI->new('a.0=3&a.2=4&b.c.0=x') );

       Or, as an imported function for convenience:

           use CGI::Expand;
           use CGI; # or Apache::Request, etc.

           $args = expand_cgi( CGI->new('a.0=3&a.2=4&b.c.0=x') );
           # $args = { a => [3,undef,4], b => { c => ['x'] }, }

           # Or to catch exceptions:
           eval {
               $args = expand_cgi( CGI->new('a.0=3&a.2=4&b.c.0=x') );
           } or log_and_exit( $@ );

           #-----
           use CGI::Expand qw(expand_hash);

           $args = expand_hash({'a.0'=>77}); # $args = { a => [ 77 ] }

DESCRIPTION

       Converts a CGI query into structured data using a dotted name convention similar to TT2.

       "expand_cgi" works with CGI.pm, Apache::Request or anything with an appropriate "param"
       method.  Or you can use "expand_hash" directly.

       If you prefer to use a different flattening convention then CGI::Expand can be subclassed.

MOTIVATION

       The Common Gateway Interface restricts parameters to name=value pairs, but often we'd like
       to use more structured data.  This module uses a name encoding convention to rebuild a
       hash of hashes, arrays and values.  Arrays can either be indexed explicitly or from CGI's
       multi-valued parameter handling.

       The generic nature of this process means that the core components of your system can
       remain CGI ignorant and operate on structured data.  Better for modularity, better for
       testing.

DOT CONVENTION

       The key-value pair "a.b.1=hi" expands to the perl structure:

         { a => { b => [ undef, "hi" ] }

       The key ("a.b.1") specifies the location at which the value ("hi") is stored.  The key is
       split on '.' characters, the first segment ("a") is a key in the top level hash,
       subsequent segments may be keys in sub-hashes or indices in sub-arrays.  Integer segments
       are treated as array indices, others as hash keys.

       Array size is limited to 100 by default.  The limit can be altered by subclassing or using
       the deprecated $Max_Array package variable.  See below.

       The backslash '\' escapes the next character in cgi parameter names allowing '.' , '\' and
       digits in hash keys.  The escaping '\' is removed.  Values are not altered.

   Key-Value Examples
         # HoHoL
         a.b.1=hi ---> { a => { b => [ undef, "hi" ] }

         # HoLoH
         a.1.b=hi ---> { a => [ undef, { b => "hi" } ] }

         # top level always a hash
         9.0=hi   ---> { "9" => [ "hi" ] }

         # can backslash escape to treat digits hash as keys
         a.\0=hi     ---> { "a" => { 0 => "hi"} }

         # or to put . and \ literals in keys
         a\\b\.c=hi  ---  { 'a\\b\.c' => "hi" }

METHODS / FUNCTIONS

       The routines listed below are all methods, but can be imported to be called as functions.
       In other words, you can call "CGI::Expand->expand_hash(...)"  or you can import
       "expand_hash" and then call "expand_hash(...)" without using method invocation syntax.

       "expand_cgi" is exported by default. "expand_hash" and "collapse_hash" are exported upon
       request.

       expand_cgi
               my $deep_hash = expand_cgi ( $CGI_object_or_similar );

           Takes a CGI object and returns a hashref for the expanded data structure (or dies, see
           "EXCEPTIONS").

           Wrapper around expand_hash that uses the "param" method of the CGI object to collect
           the names and values.

           Handles multivalued parameters as array refs (although they can't be mixed with
           indexed arrays and will have an undefined ordering).

               $query = 'a.0=3&a.2=4&b.c.0=x&c.0=2&c.1=3&d=&e=1&e=2';

               $args = expand_cgi( CGI->new($query) );

               # result:
               # $args = {
               #   a => [3,undef,4],
               #   b => { c => ['x'] },
               #   c => ['2','3'],
               #   d => '',
               #   e => ['1','2'], # order depends on CGI/etc
               # };

       expand_hash
               my $deep_hash = expand_hash( $flat_hash );

           Expands the keys of the parameter hash according to the dot convention (or dies, see
           "EXCEPTIONS").

               $args = expand_hash({ 'a.b.1' => [1,2] });
               # $args = { a => { b => [undef, [1,2] ] } }

       collapse_hash
               my $flat_hash = collapse_hash( $deep_hash );

           The inverse of expand_hash.  Converts the $deep_hash data structure back into a flat
           hash.

               $flat = collapse_hash({ a => { b => [undef, [1,2] ] } });
               # $flat = { 'a.b.1.0' => 1, 'a.b.1.1' => 2 }

EXCEPTIONS

       WARNING: The users of your site can cause these exceptions so you must decide how they are
       handled (possibly by letting the process die).

       "CGI param array limit exceeded..."
           If an array index exceeds the array limit (default: 100) then an exception is thrown.

       "CGI param clash for..."
           A cgi query like "a=1&a.b=1" would require the value of $args->{a} to be both 1 and {
           b => 1 }.  Such type inconsistencies are reported as exceptions.  (See test.pl for for
           examples)

SUBCLASSING

       Subclassing in now the preferred way to change the behaviour and defaults.  (Previously
       package variables were used, see test.pl).

       The methods which may be overridden by subclasses are separator, max_array, split_name and
       join_name.

       max_array
               $subclass->max_Array;

           The limit for the array size, defaults to 100.  The value 0 can be used to disable the
           use of arrays, everthing is a hash key.

       separator
               $subclass->separator;

           Returns the separator characters used to split the keys of the flat hash.  The default
           is '.' but multiple characters are allowed.  The default join will use the first
           character.

           If there is no separator then '\' escaping does not occur.  This is for use with
           split_name and join_name below.

       split_name
               my @segments = $subclass->split_name($name);

           The split_name method must break $name in to key segments for the nested data
           structure.  The default version just splits on the separator characters with a bit of
           fiddling to handle escaping.

       join_name
               my $name = $subclass->join_name(@segments);

           The inverse of split_name, joins the segments back to the key for the flat hash.  The
           default version uses the first character of the string returned by the separator
           method.

DEPRECATIONS

       $CGI::Expand::Separator and $CGI::Expand::Max_Array are deprecated.  They still work for
       now but emit a warning (supressed with $CGI::Expand::BackCompat = 1)

       Using the functions by their fully qualified names ceased to work at around version 1.04.
       They're now class methods so just replace the last :: with ->.

LIMITATIONS

       The top level is always a hash.  Consequently, any digit only names will be keys in this
       hash rather than array indices.

       Image inputs with name.x, name.y coordinates are ignored as they will class with the value
       for name.

TODO

       Thing about ways to keep $cgi and the expanded version in sync

       Glob style parameters (with SCALAR, ARRAY and HASH slots) would resolve the type clashes,
       probably no fun to use.  Look at using Template::Plugin::StringTree to avoid path clashes

SEE ALSO

       •   HTTP::Rollup - Replaces CGI.pm completely, no list ordering.

       •   CGI::State - Tied to CGI.pm, unclear error checking

       •   Template::Plugin::StringTree

       •   Hash::Flatten - Pick your delimiters

       •   http://template-toolkit.org/pipermail/templates/2002-January/002368.html

       •   There's a tiny and beautiful reduce solution somewhere on perlmonks.

AUTHOR

       Brad Bowman <cgi-expand@bereft.net>

       Pod corrections: Ricardo Signes

COPYRIGHT

       Copyright (C) 2004-2013, Brad Bowman.

LICENSE

       CGI::Expand is free software; you can redistribute it and/or modify it under the terms of
       either:

       a) the GNU General Public License as published by the Free Software Foundation; either
       version 1, or (at your option) any later version, or

       b) the "Artistic License" which comes with Perl.

       For more details, see the full text of the licenses at
       <http://www.perlfoundation.org/artistic_license_1_0>, and
       <http://www.gnu.org/licenses/gpl-1.0.html>.