All Mixed Up - Perl

The flip side of whatever you just read is, of course, deserialization. Perl's WDDX.pm module accomplishes this via its deserialize() method, which can be used to convert WDDX-based language-independent data representations into native data types.

Consider the following example, which demonstrates how a WDDX packet containing a string value is deserialized into a Perl scalar variable:

#!/usr/bin/perl
# use WDDX module
use WDDX;
# create WDDX object
$wddx = new WDDX;
# simulate a WDDX packet
$packet = "<wddxPacket version='1.0'><header/><data><string>Robin
Hood</string></data></wddxPacket>";
# deserialize packet into WDDX string object
$obj = $wddx->deserialize($packet);
# check object type 
if ($obj->type eq "string")
{
# and print as scalar
print $obj->as_scalar;
}

In this case, the WDDX packet is first deserialized into a WDDX string object, and then the string object's as_scalar() method is used to convert the string object into a native Perl scalar. Note that the deserialized object exposes a type() method, which can be used to identify the data type and process it appropriately.

Here's the output:

Robin Hood

This deserialization works with arrays too - as the following example demonstrates:

#!/usr/bin/perl
# use WDDX moduleuse WDDX;# create WDDX object$wddx = new WDDX;# simulate a WDDX packet$packet = "<wddxPacket version='1.0'> <header/> <data> <arraylength='3'> <string>red</string> <string>blue</string><string>green</string> </array> </data> </wddxPacket>";# deserialize packet into WDDX array object$obj = $wddx->deserialize($packet);# get number of elements in array$length = $obj->length();# get reference to native Perl array$arrayref = $obj->as_arrayref();# iterate through array and print elementsfor ($i=0; $i<$length; $i++){ print "$$arrayref[$i]\n";}

Here's the output:

red
bluegreen

Wanna really cause some heartburn? Try serializing an array of arrays,

#!/usr/bin/perl
# include moduleuse WDDX;# create WDDX objectmy $wddx = new WDDX;# create an arraymy @arr = ( $wddx->string("huey"), $wddx->string("dewey"),$wddx->boolean(1) );# create a WDDX hash$obj = $wddx->struct( { "str" => $wddx->string("Abracadabra"), "num" => $wddx->number(23), "arr" => $wddx->array(\@arr) });# serialize and print objectprint $wddx->serialize($obj);

and see what you get:

<wddxPacket version='1.0'>
<header/><data><struct><var name='num'><number>23</number></var><var name='str'><string>Abracadabra</string></var><var name='arr'><array length='3'><string>huey</string><string>dewey</string><boolean value='true'/></array></var></struct></data></wddxPacket>

This is a hash with three keys, one containing a string, the second a number, and the third an array. Now, try deserializing the WDDX packet generated from the code above.

#!/usr/bin/perl
# use WDDX moduleuse WDDX;# create WDDX object$wddx = new WDDX;# simulate a WDDX packet$packet = " <wddxPacket version='1.0'><header/><data><struct><varname='num'><number>23</number></var><varname='str'><string>Abracadabra</string></var><var name='arr'><arraylength='3'><string>huey</string><string>dewey</string><booleanvalue='true'/></array></var></struct></data></wddxPacket>";# deserialize packet into WDDX array object$obj = $wddx->deserialize($packet);# get reference to native Perl hash$hashref = $obj->as_hashref();# get keys@k = $obj->keys();# print keys and type of corresponding valuesforeach $k (@k){ print "$k --> " . $obj->get($k)->type . "\n";}

Here's what you should see:

num --> number
str --> stringarr --> array

>>> More Perl Programming Articles          >>> More By icarus, (c) Melonfire

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