design-nation.blog/en: Data structures: Hash table

February 17, 2004

Data structures: Hash table

A hash table is a short of collection of linked lists. It allows us to store pairs data-object, and later retrieve the data using its key

You can view a detailled explanation of what a hash map is here

And you can download my AS2 implementation here

To test it you could try something like this:

import net.designnation.structs.*


var a: HashMap= new HashMap( );

// Setitem
//
key= "4";
trace( "Adding "+ key );
a.setItem( key, new Object( key ) );
trace( "HashMap contents: "+ a );

key= "21";
trace( "Adding "+ key );
a.setItem( key, [ "a1", "a2" ] );
trace( "HashMap content: "+ a );

key= "5";
trace( "Adding "+ key );
a.setItem( key, new Object( key ) );
trace( "HashMap content: "+ a );

key= "8";
trace( "Adding "+ key );
a.setItem( key, new Object( key ) );
trace( "HashMap content: "+ a );

key= "81";
trace( "Adding "+ key );
a.setItem( key, new Object( key ) );
trace( "HashMap content: "+ a );

key= "8";
trace( "Adding "+ key );
a.setItem( key, new Object( key ) );

key= "8";
trace( "Retrieving "+ key );
trace( a.getItem( key ).toString(  ) );
// Count
//
trace( "Count: "+ a.count(  ) );

// Remove
//
key= "4";
trace( "Removing "+ key );
a.remove( key );
trace( "HashMap content: "+ a.toString(  ) );
trace( "Count: "+ a.count(  ) );

Good night!

Posted by Cesar Tardaguila Date: February 17, 2004 12:40 AM | TrackBack

Comments

is there also a method to check the existence of a key (e.g. hasItem())?

Would it be possible for you to send me the as source if your HashMap class. I don't know where flash installs these mxp files, therefore I couldn't take a look into the classe files and find out the provided functions by myself.

regards,
paul

Posted by: Paul en: March 7, 2004 09:08 PM

Hi, Paul.

I haven't implemented any method to check for a key yet, but I'll try to do it as soon as possible.

The as files are installed in the following folder ( windows, I don't know about macs ):

C:\documents and settings\{user}\Local configuration\Program data\Macromedia\FlashMX2004\{language}\Configuration\Classes

There is a folder called "net", containing my as files.

Posted by: Cesar Tardaguila en: March 7, 2004 10:31 PM

thanks for your help, I found the as files.

did you perform some test comparing the access time of your HashMap and a normal assoiative Array?
Is there a size limit you would suggest for the HashMap? I am planing on using it as a cache object to store product-data in but it could become quite large (200-300 items or more), do you think this would still be ok?

Thanks a lot for your help,

Regards,
Paul

Posted by: Paul en: March 8, 2004 10:11 AM

Hi, Paul, sorry for the delay.

I think this structure should be ok to store much more than 300 items. I've tested it with 500 objects ( movieclips ) and there was no problem.

Anyway, I'm planing to update it this weekend, to try to improve the performance, so if you can wait untill sunday...

Posted by: Cesar Tardaguila en: March 9, 2004 08:25 PM