Provided by: libcgi-expand-perl_2.05-4_all 
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>.