Is it a Hash Brown?

It has been one crazy semester (I think the lack of activity can vouch for that). I've come up to the surface and see that a lot of the landscape has changed, take the emergence of CodeGear for example. I am hoping this is a breathe of new life that can revitalize the Delphi community and not just a last ditch effort (personally I think the BDS IDE is far better for development than VS). I am optimistic about the whole thing and hope they endure the 'rebirth process'.

As I was submerged in my own little world for a period of time, I had the need to calculate the Hash value for files. This actually turned out to server two purposes. The first being the verification of a file as original (intact) by comparing the hash value of the current and original file. Second, it turned out to be a fast way of identifying identical files. Often times a CRC is used to calculate a checksum, however I opted to make use of the System.Security.Cryptography Namespace. This Namespace has a number of useful hash functions including SHA1, SHA256 and SHA512. Surprisingly (or not) these are relatively easy to use and eliminate the need to formulate the algorithm on your own. Here it is in a couple of worlds:

Delphi:

uses
System.Security.Cryptography, System.IO;

procedure frmMain.ClearForm;
begin
txtSHA1.Text:= '';
txtSHA256.Text:= '';
txtSHA512.Text:= '';
end;

procedure frmMain.txtFileName_TextChanged(sender: System.Object; e: System.EventArgs);
begin
ToolTip1.SetToolTip(txtFileName,txtFileName.Text);
end;

procedure frmMain.btnCalculate_Click(sender: System.Object; e: System.EventArgs);
var
myCursor: System.Windows.Forms.Cursor;
oFileStream: FileStream;
lBytes: int64;
instance: FileInfo;
filecontents: Array of Byte;
result: Array of Byte;
SHA1M: SHA1Managed;
SHA256M: SHA256Managed;
SHA512M: SHA512Managed;

begin
myCursor:= Cursor;
Cursor:= Cursors.WaitCursor;
try
try
if not(txtFileName.Text='') then
begin
ErrorProvider1.SetError(btnFile,'');

instance:= FileInfo.Create(txtFileName.Text);
oFileStream:= instance.OpenRead;
lBytes:= oFileStream.Length;
SetLength(filecontents,lBytes);
oFileStream.Read(filecontents,0,lBytes);
oFileStream.Close;

SHA1M:= SHA1Managed.Create;
result:= SHA1M.ComputeHash(filecontents);
txtSHA1.Text:= Convert.ToBase64String(result);

SHA256M:= SHA256Managed.Create;
result:= SHA256M.ComputeHash(filecontents);
txtSHA256.Text:= Convert.ToBase64String(result);

SHA512M:= SHA512Managed.Create;
result:= SHA512M.ComputeHash(filecontents);
txtSHA512.Text:= Convert.ToBase64String(result);
end
else
begin
ErrorProvider1.SetError(btnFile,'Select a filename');
end;
except
on e: exception do
MessageBox.Show(e.Message, e.Source, MessageBoxButtons.OK,
MessageBoxIcon.Error);
end;
finally
Cursor:= myCursor;
end;
end;

procedure frmMain.btnFile_Click(sender: System.Object; e: System.EventArgs);
begin
if (ofdFileName.ShowDialog = System.Windows.Forms.DialogResult.OK) then
begin
ClearForm;
txtFileName.Text:= ofdFileName.FileName;
end;
end;

VB:

Imports System.Security.Cryptography
Imports System.IO

Public Class frmMain

Private Sub btnFile_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnFile.Click
If ofdFileName.ShowDialog Then
ClearForm()
txtFileName.Text = ofdFileName.FileName
End If
End Sub

Private Sub txtFileName_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtFileName.TextChanged
ToolTip1.SetToolTip(txtFileName, txtFileName.Text)
End Sub

Private Sub ClearForm()
txtSHA1.Text = ""
txtSHA256.Text = ""
txtSHA512.Text = ""
End Sub

Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
Dim myCursor As Cursor
Dim oFileStream As System.IO.FileStream
Dim lBytes As Long
Dim result() As Byte

myCursor = Cursor
Cursor = Cursors.WaitCursor
Try

If Not (txtFileName.Text = "") Then
ErrorProvider1.Clear() 'Introduced .NET 2.0

Dim instance As New FileInfo(txtFileName.Text)
oFileStream = instance.OpenRead()
lBytes = oFileStream.Length
Dim filecontents(lBytes) As Byte
oFileStream.Read(filecontents, 0, lBytes)
oFileStream.Close()

Dim sha1M As New SHA1Managed
result = sha1M.ComputeHash(filecontents)
txtSHA1.Text = Convert.ToBase64String(result)

Dim sha256M As New SHA256Managed
result = sha256M.ComputeHash(filecontents)
txtSHA256.Text = Convert.ToBase64String(result)

Dim sha512M As New SHA512Managed
result = sha512M.ComputeHash(filecontents)
txtSHA512.Text = Convert.ToBase64String(result)
Else
ErrorProvider1.SetError(btnFile, "Select a filename")
End If

Catch ex As Exception
MessageBox.Show(ex.Message, ex.Source, MessageBoxButtons.OK, MessageBoxIcon.Error)

Finally
Cursor = myCursor
End Try
End Sub

End Class

This is another post done with Live Writer, I think it is pretty 'groovy'.

Posted on Sunday, December 17, 2006 8:04 AM by Brad Prendergast

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Who does not like cookies?

As I was doing some odd exploration of an older ASP application I decided to do some experimentation with cookies. As with most of my posts I try to drop things back significantly allowing for some basic examples. Cookies are a way for a web application to store specific information. Cookies are small text files that are stored on a client machine and are contained in the Response and Request traffic between a client and host computer. Web applications can read cookies whenever a user visits the site. Information such as user preferences could be stored in a cookie.

Within .NET there the HttpCookie Class is used for dealing with cookie information. Basic dealing with cookies is a lot easier than it may initially sound. I was able to put together a sample application that stores a textbox, validated textbox and calendar date (cookies store strings) in a cookie in only a few minutes.

Start a new ASP.NET Web Application from within BDS2006. On the default design form place a two text boxes, a calendar control, a RegularExpressionValidator and three buttons. I also placed some labels for identification.

Label1: System.Web.UI.WebControls.Label;
txtName: System.Web.UI.WebControls.TextBox;
btnWrite: System.Web.UI.WebControls.Button;
btnRead: System.Web.UI.WebControls.Button;
btnClear: System.Web.UI.WebControls.Button;
Calendar1: System.Web.UI.WebControls.Calendar;
txtEmail: System.Web.UI.WebControls.TextBox;
Label3: System.Web.UI.WebControls.Label;
RegularExpressionValidator1: System.Web.UI.WebControls.RegularExpressionValidator;
Label4: System.Web.UI.WebControls.Label;


Set the properties for RegularExpression1 as follows:
// This checks for a proper email address
ValidationExpression:= ‘\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*’;
ControlToValidate:= txtEmail;
ErrorMessage:= ‘Invalid Email’;

The following is the code behind the page (For maintenance, I’d use constants for the value and cookie names):
procedure TWebForm1.Page_Load(sender: System.Object; e: System.EventArgs);
begin
// The calendar defaults to a selected date of 01/01/0001
if Calendar1.SelectedDate = DateTime.Parse('01/01/0001') then
Calendar1.SelectedDate:= DateTime.Now;
end;

procedure TWebForm1.btnClear_Click(sender: System.Object; e: System.EventArgs);
var
hc: HttpCookie;
begin
if Request.Cookies['MySite'] nil then
begin
hc:= Request.Cookies['MySite'];
// This method may work, however the proper way to clear a cookie
// is to set the cookie to have a prior expiration date
// hc.Values.Clear;
// Response.Cookies.Add(hc);
// Calendar1.SelectedDate:= DateTime.Now;
hc.Expires:= DateTime.Now.AddDays(-100);
txtName.Text:='';
txtEmail.Text:= '';
Calendar1.SelectedDate:= DateTime.Now;
end;
end;

procedure TWebForm1.btnRead_Click(sender: System.Object; e: System.EventArgs);
var
hc: HttpCookie;
begin
if Request.Cookies['MySite'] nil then
begin
txtEmail.Text:= Request.Cookies['MySite'].Values['email'];
txtName.Text:= Request.Cookies['MySite'].Values['name'];
Calendar1.SelectedDate:= DateTime.Parse(Request.Cookies['MySite'].Values['date']);
end
else
begin
txtEmail.Text:= '';
txtName.Text:= '';
Calendar1.SelectedDate:= DateTime.Now;
end;
end;

procedure TWebForm1.btnWrite_Click(sender: System.Object; e: System.EventArgs);
var
hc: HttpCookie;
begin
if RegularExpressionValidator1.IsValid then
begin
hc:= HttpCookie.Create('MySite');
hc.Values['name']:= txtName.Text;
hc.Values['email']:= txtEmail.Text;
hc.Values['date']:= Calendar1.SelectedDate.ToShortDateString;
// Expire cookie in 1hour. Always set an expiration
// if you do not set an expiration date the cookie is not
// stored; it will be treated as a session variable
// DateTime.MaxValue will make it last forever
hc.Expires:= DateTime.Now.AddHours(1);
Response.Cookies.Add(hc);
end;
end;


For some more information take a look at ASP.NET Cookies Overview on MSDN. Another valuable link is How to Share Session State Between Classic ASP and ASP.NET.

Posted on Saturday, July 8, 2006 6:47 PM by Brad Prendergast

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DayLightTime

In an attempt to better understand what’s available and come up with new ways of doing things, I often browse through various class definitions. As I was browsing through some classes this morning, I came across the DaylightTime Class. The DaylightTime Class is part of the System.Globalization namespace. This class is used to define the period of daylight-savings time. The GetDaylightChanges Method of the TimeZone Class returns a timezone’s DaylightTime for a specified year. This may not all sound so interesting, however using this in an ASP.NET application a semi-useful utility can be developed. This example also shows how to dynamically work with a System.Web.UI.WebControls.Table Class. Dynamically created table data is not persistent and would need to be ‘refreshed’ on each postback page display. In this example I just use one row for displaying a year’s calculation. A System.Web.UI.WebControls.RangeValidator is also used in this demonstration. Check out my new DayLightTime Display.



In the page class:


public
localzone: TimeZone;
daylight: System.Globalization.DaylightTime;
tr: TableRow;
tcYear,
tcStart,
tcEnd,
tcChange: TableCell;

procedure TWebForm1.Page_Load(sender: System.Object; e: System.EventArgs);
begin
localzone:= TimeZone.CurrentTimeZone;
lblTimeZone.Text:= localzone.StandardName;
//txtYear.Text:= '1999';
end;

procedure TWebForm1.btnProcess_Click(sender: System.Object; e: System.EventArgs);
var
year: Integer;
begin
if RangeValidator1.IsValid then
begin
try
year:= Convert.ToInt32(txtYear.Text);
except
//dynamically setting it to the current year
//is also an option
year:= 2006;
txtYear.Text:= year.ToString;
end;
tblOutput.Rows.Add(CreateDaylightRow(year));
end;
end;

function TWebForm1.CreateDaylightRow(year: integer): TableRow;
begin
daylight:= localzone.GetDaylightChanges(year);

tr:= TableRow.Create;

tcYear:= TableCell.Create;
tcStart:= TableCell.Create;
tcEnd:= TableCell.Create;
tcChange:= TableCell.Create;

tcYear.Text:= year.ToString;
tr.Cells.Add(tcYear);

tcStart:= TableCell.Create;
tcStart.HorizontalAlign:= HorizontalAlign.Right;
tcStart.Text:= daylight.Start.ToString('yyyy-MM-dd HH:mm');
tr.Cells.Add(tcStart);

tcEnd:= TableCell.Create;
tcEnd.HorizontalAlign:= HorizontalAlign.Right;
tcEnd.Text:= daylight.&End.ToString('yyyy-MM-dd HH:mm');
tr.Cells.Add(tcEnd);

tcChange:= TableCell.Create;
tcChange.HorizontalAlign:= HorizontalAlign.Right;
tcChange.Text:= daylight.Delta.ToString;
tr.Cells.Add(tcChange);

Result:= tr;
end;

Posted on Saturday, July 1, 2006 8:50 AM by Brad Prendergast

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