Thursday, September 04, 2008

Tuesday, September 02, 2008

Credit Card number validator for Delphi

We are implementing parts of a global electronic payment solution and one of the mandatory features was to verify credit card numbers. This is done using the Luhn algorithm. I was expecting to find a wide variety of implementations on our sexy Delphi language but to my surprise there were very few hits on my search.

So, for others that may needed, I'm including this small routine that validates the credit card number (not the card secure code, nor the expiration date). There are several implementations on the web that based on the card prefix digits you can determine the kind of card you are looking at (VISA, MC, Dinners, etc.) That kind of inferences are not reliable for a global solution so the decision was made to drop that auto detection.

function ValidateCreditCardNumber(CreditCardNumber:string):boolean;

Const
DigitsAllowed = ['0'..'9'];
MaxCCSize = 19;
MinCCSize = 13;

var
i : integer;
CleanCardNumber: string;
digit: Integer;
CheckSum: Integer; { Holds the value of the operation }
Flag: Boolean; { used to indicate when ready }
Counter: Integer; { index counter }
PartNumber: string; { used to extract each digit of number }
Number: Integer; { used to convert each digit to integer}


Begin
CleanCardNumber:='';
digit:=0;

// Remove any non numeric value
for I := 1 to Length(CreditCardNumber) do
Begin
if CreditCardNumber[i] in DigitsAllowed then
CleanCardNumber:= CleanCardNumber + CreditCardNumber[i];
End;

// Check for valid card length number
if (Length(CleanCardNumber)MaxCCSize) then
Begin
Result:= False;
Exit;
End;

// get the starting value for our counter
Counter := Length(CleanCardNumber);
CheckSum := 0;
PartNumber := '';
Number := 0;
Flag := false;

while (Counter >= 1) do
begin
// get the current digit
PartNumber := Copy(CleanCardNumber, Counter, 1);
Number := StrToInt(PartNumber); // convert to integer
if (Flag) then // only do every other digit
begin
Number := Number * 2;
if (Number >= 10) then
Number := Number - 9;
end;
CheckSum := CheckSum + Number;

Flag := not (Flag);

Counter := Counter - 1;
end;

result := ((CheckSum mod 10) = 0);

End;

This implementation is based on a 1996 VB Code migration from Shawn Wilson.

Thursday, July 17, 2008

Tiburón swimming in Lake Ontario.

For the first time, a Tiburón was found last night swimming around the North York Public Library and people is wondering if they are coming out from Lake Ontario.

But, such a thing seems to be untrue. All points out that our visitor came from Silicon Valley.

Yup!, we had the pleasure to listen to no other than legend CodeGear developer David Intersimone and Anders Ohlsson (geesh, hope i got his lastname right). They gave us a good talk about CodeGear, Embarcadero and tour of Tiburón, called now officialy "Delphi 2009".

The highly expected Unicode support is everywhere and it seems that the guys put lots of effort on achieving a high degree of backwards compatibility, which is as usual, a fantastic tradition that thankfully Delphi has never lost.

Lots of new classes to help us on this transition, some new enhancements to the VCL (some cool new components there) which you probably already saw on all the blog posts that CodeGear is generating now.

BUT, now lets talk about those hidden gems that we could see while they were demoing stuff, for example, a new little category to the component tool palette, something called "Ribbon Components", yup, they didn't mention it, they didn't demo them, but it was there. So, no NDA violation here, nor there, merely healthy speculation.

Also I noticed two more categories, and I am extremely happy about them, because it means that we are finally getting some love on the middle tier area. It seems to be part of the announced improvements to DataSnap, a "Data Snap Client" and "Data Snap Server" categories, instead of the typical single "DataSnap" group. What is in there, no idea, but hey, i like the hint.


Anyway, it was a great time, a great experience, Delphi is getting better. The guys seemed to be pump about the future, and so are we.


Oh, and did I mention that we are hiring? :)


Tuesday, April 29, 2008

How to create a Web Server Control in ASP.Net with Delphi 2007

We were presented with the challenge of creating our own server controls. After some research on the web, we found very few examples regarding how to do this, even less if they are specifically targeted to Delphi.Net 2007.

So, in order to help the next fellow Delphi developer that is presented with similar situations, it is our objective to publish small articles on every new item that we face in our development process as a contribution to the new Spirit of Delphi that is growing in the community.

Special thanks to Feryal Badili for putting this article together. :)

Here is the step-by-step instruction on how to create a simple server control in Delphi 2007.

Well, there are two ways to create web components in Delphi:
1) You can go to 'File-New-Other-Delphi for .NET Projects' and choose 'Web Control Library'.
2) OR, you can go to 'File-New-Other-Delphi for .NET Projects' and choose 'Package'. Then in project manager panel, right click on 'Contains' folder and select 'Add new-Other-Delphi for .NET Projects-New ASP.NET Files' and select 'Web Custom Control'. You may want to use this approach if you would like to have multiple controls in the same package.

The general recommendation is to use the first method to create a web custom control for the first time, it is a lot easier in the long run, believe me.

Delphi will generate the source code for a very simple web control. Let's just try to understand it:

The default name for the file is 'WebControl1.pas' . It is a Delphi unit file and the unit name is really your namespace. You need to remember that because you're going to need it later when you are using the control in your web page!

Under 'Type' section of the code, you will see the following lines:

[DefaultProperty('Text'), ToolboxData('<{0}:MyWebControl1 runat=server>')] MyWebControl1 = class(System.Web.UI.WebControls.WebControl)

Well, what does it mean?
Your class MyWebControl1 is derived from System.Web.UI.WebControls.WebControl.

If your control renders a user interface (UI) element or any other visible element on the client, you should derive your control from System.Web.UI.WebControls.WebControl (or a derived class).

If your control renders an element that is not visible in the client browser, such as a hidden element or a meta element, derive your control from System.Web.UI.Control. The WebControl class derives from Control and adds style-related properties such as Font, Forecolor, and BackColor.

In addition, a control that derives from WebControl participates in the themes features of ASP.NET without any extra work on your part. If your control extends the functionality of an existing control, such as the Button, Label, or Image controls, you can derive from that control.
If you are going to have multiple visual controls in your server component and you wish to inherit the basic functionality of the parent controls, you need to derive your class from CompositeControl class:
MyWebControl1 = class(System.Web.UI.WebControls.CompositeControl)
To learn more about composite controls, see:
http://msdn2.microsoft.com/en-us/library/3257x3ea(VS.80).aspx

The code inside brackets that is generated on top of your class definition is attributes that apply to your class. To learn more about these attributes, see the following link:
http://msdn2.microsoft.com/en-us/library/ms178658(VS.80).aspx

The code generated by Delphi adds a property called 'Text' to your component . Since this property is published, you will be able to see it in the "IntelliSense" or "Code Completion" and object inspector when you use this component in a web page.

As you can see, this property also has some attributes:
Bindable: set it to true if your property can be data bound.
Category: In object inspector, this property will appear under the category(group) that you define.
DefaultValue: Obviously, this is the default value of your property.

You need to define these attributes for each and every property that you want to publish for your component. Also pay attention to the field definition for your property.

Next step is to add your own child controls and render the server control. In order to do that, you need to implement the following procedures:

procedure CreateChildControls(); override; procedure RenderContents(Output: HtmlTextWriter); override;

Here is an example of simple server control that includes only one control (TextBox) and adds one property named 'ShowTime' to the control.

You can use this component in both Visual studio or Delphi .NET.

unit WebControl1;
// To create a more advanced Web Control that supports live data at
// design time, see instructions in the readme file located in the
// 'BDS\5.0\Source\DotNet\dbwebcontrols' directory
//

interface

uses
system.web,
System.Web.UI,
System.Web.UI.WebControls,
System.ComponentModel,
system.Drawing,
System.Data,
system.security.Permissions;

type
///
/// Summary description for the component
///


[
AspNetHostingPermission(SecurityAction.Demand,
Level = AspNetHostingPermissionLevel.Minimal),
AspNetHostingPermission(SecurityAction.InheritanceDemand,
Level=AspNetHostingPermissionLevel.Minimal),
DefaultProperty('ShowTime'),
ToolboxData('<{0}:OpenItems runat=server>')
]
OpenItems = class(System.Web.UI.WebControls.CompositeControl)
strict private
IsError : boolean;

msgBox : textBox;
FShowTime: boolean;

strict protected
procedure RecreateChildControls(); override;
protected
procedure RenderContents(Output: HtmlTextWriter); override;
procedure CreateChildControls(); override;
public
constructor Create;
published
[Bindable(false),
Category('Behavior'),
DefaultValue(false),
Description('Show the Date and Time')
]
property ShowTime : boolean read FShowTime write FShowTime;
end;

implementation
uses SysUtils;

///
/// Define a public parameterless constructor needed by web controls.
///

constructor OpenItems.Create;
begin
inherited;
isError := false;
end;

procedure OpenItems.RecreateChildControls();
begin
try
EnsureChildControls();
except
IsError := false;
end;
end;

procedure OpenItems.CreateChildControls();

begin
try

Controls.Clear();

// Create a text box
msgBox := TextBox.Create;

if ShowTime then
msgBox.Text := DateTimeToStr(Now)
else
msgBox.Text := DateToStr(Now);

msgBox.BorderStyle := System.Web.UI.WebControls.BorderStyle(1); // Sets border style to 'None'
msgBox.ForeColor := System.Drawing.Color.get_Red;
msgBox.Style.Item['position'] := 'reletive';
self.Controls.Add(msgBox);
except
IsError := false;
end;

end;

///
/// Render this control to the output parameter specified, preserving
/// cosmetic attribute output generation inherited from standard
/// WebControl.
///

///


{$REGION 'Render override'}
procedure OpenItems.RenderContents(Output: HtmlTextWriter);
begin

if not IsError then
begin
// There was no error so far, render all components
try
AddAttributesToRender(output);

Output.AddAttribute(HtmlTextWriterAttribute.Cellpadding,'1', false);

Output.RenderBeginTag(HtmlTextWriterTag.Table);
// The table will be very useful when you have multiple visual controls
// included in your component

Output.RenderBeginTag(HtmlTextWriterTag.Tr);
Output.RenderBeginTag(HtmlTextWriterTag.Td);
msgBox.RenderControl(output);
Output.RenderEndTag(); // end td
Output.RenderEndTag(); // end tr

Output.RenderEndTag();

except
// An error happened, just show a message
Output.Write(' '+ 'Unable to create the components');
end;

end else begin
// An error happened, just show a message
Output.Write(' '+ 'Unable to create the components');
end;

end;

{$ENDREGION}

end.


Monday, April 21, 2008

Creating extended stored procedures on Delphi.

Well, originally we were going to implement a sexy Delphi.Net CLR Based Stored procedure now that we are using MSSQL 2005 and hearing all the good things about this highly publicized feature. Sadly, we hit the wall after initial testings showed us the big amount of limitations on the assemblies that we could use and all the exceptions we must made to make it work on MSSQL 2005. For example:

* First, you need to enable CLR on the database. (Thats ok.)
* Classes must be public and static. (Makes it harder, but we can manage it)
* Avoid namespaces with anything that is not the list of "safe" name spaces approved by Microsoft. (mmm)
* "Safe" assembly is simply a way of saying "non-microsoft built" assembly. You have a couple more "modes" on how to install your assembly on MSSQL, but as you can read below (MSSQL Online help), it gets touchy, and probably complicated. (yeah, I tried it, got ugly)

To create an EXTERNAL_ACCESS or UNSAFE assembly in SQL Server, one of the following two conditions must be met:
The assembly is strong name signed or Authenticode signed with a certificate. This strong name (or certificate) is created inside SQL Server as an asymmetric key (or certificate), and has a corresponding login with EXTERNAL ACCESS ASSEMBLY permission (for external access assemblies) or UNSAFE ASSEMBLY permission (for unsafe assemblies).
The database owner (DBO) has EXTERNAL ACCESS ASSEMBLY (for EXTERNAL ACCESS assemblies) or UNSAFE ASSEMBLY (for UNSAFE assemblies) permission, and the database has the TRUSTWORTHY Database Property set to ON. “

* MSSQL will complaing about the CodeGear assemblies being unsafe, some tweaking is necessary.

* Third party assemblies are not welcome on MSSQL. i.e. RemObjects.

Well, in summary, after playing with it, adding our assemblies required a lot of code trimming and removing any namespace that has any reference to anything visual (makes sense) even if it is not being used at all. Finally, the detail that just finish helping us to dropped the idea was that we don't have the source code for those "extra" assemblies (RemObjects) that we required and the amount of trimming just got out of control.

With one option out we went back to the drawing board with the plan to extend and update an old implementation of "Old School" extended stored procedures, as soon as I open that old project I realized why I never liked working with it, parsing the parameters, checking their types, defining data columns to return a proper record set was simply a big painful and slow process.

Thankfully, I was able to find in the vault of memories a great presentation by Berend de Boer made in Inprise DevCon '99 where he explains the general steps to implement them and even included a great piece of source code of the mighty "TSQLXProc" object that simply takes over the painful implementation and takes it to the Delphi way. After that finding Berend's website was easy.

For anyone needing this, check this link.

My Kudos to Berend,

EVERY DAY TIPS: Manually deleting a windows service

There I was playing with setting up subversion server running as a Windows Service until I made a tragic mistake and I get to the point of needing to remove the service that I just recently installed.

Ok, fine, as a good Delphi guy, I went looking for that sexy graphic console (Service Manager) that will give me the all mighty power to delete the service, but, I hit a wall after realizing that such an option was disabled for me.

So, after googling a bit I found two nice options.

1. If you remember the exact name of the service (not the description), you can use the sc command:
C:\>sc delete "service name"

If you don't know it, then you can go straight to the registry, find your guy and delete it.

HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services

You indeed will need to restart the computer to see these changes fully reflected.

Monday, April 14, 2008

Delphi for PHP 2 en Español

Well, great news for my mother language! We have now Delphi for PHP in Spanish!.

Yup, just after the official release we are now getting the news of a translation on the Cervantes language.

Tuesday, January 01, 2008

Truncating your transaction log.

First, HAPPY NEW YEAR GUYS!!

Now, some actual blogging...

Here I was, trying to restore our metadata only database into a production server, getting constantly an error messaging saying that it was waaay to big for the available space. Well, my concern was that the entire back up of the database was only 6MB, and the database itself only contains tables with very basic data.

What is worst, the space available on that production drive was 14GB, so gosh, it simply didn't make any sense. Well, after reviewing the original metadata-only database I realized that our constant adding, updating and deleting of structures made our transaction log simply huge. (40gb)

So, after some reading I found this nice recipe to cut down the fat of your log database:

First, backup your existing log file by running
BACKUP LOG  TO DISK = ''

Now, shrink the transaction log, executing this
DBCC SHRINKFILE (, ) WITH NO_INFOMSGS

File name is the transaction log filename and target size you wanted to be, don't be too demanding on the shrinking, but as a hint, I ended up making mine only 1MB cause we don't need a log on our metadata db. :)


Update:
My apologies, the database in question is MSSQL 2005. Thanks for the feedback.