Code Example for People: Reading 32 or 64-bit Registry from a 32-bit
Application
lazarus / 34-Windows

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seier · 2012-08-30 02:22

Hi Gang,

I had so much trouble reading the 64-bit registry from a 32-bit
application that I thought I'd post the working result so others might
have less trouble in the future.  For starters, I didn't realize that
32-bit applications are segmented to a different chunk of the registry
than native 64-bit applications. 

Cheers,
Christian Blackburn

Code: [Select]uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs,
LCLType, StdCtrls, Windows;
const
    KEY_WOW64_64KEY = $000000100;

function IsWin64: boolean;
{
Detect if we are running on 64 bit Windows or 32 bit Windows,
independently of bitness of this program.
Original source:
http://www.delphipraxis.net/118485-ermitteln-ob-32-bit-oder-64-bit-
betriebssystem.html
modified for FreePascal in German Lazarus forum:
http://www.lazarusforum.de/viewtopic.php?f=55&t=5287
}
{$ifdef WIN32} //Modified KpjComp for 64bit compile mode
type
  TIsWow64Process = function( // Type of IsWow64Process API fn
      Handle: Windows.THandle; var Res: Windows.BOOL): Windows.BOOL;
stdcall;
var
  IsWow64Result: Windows.BOOL; // Result from IsWow64Process
  IsWow64Process: TIsWow64Process; // IsWow64Process fn reference
begin
  // Try to load required function from kernel32
  IsWow64Process := TIsWow64Process(Windows.GetProcAddress(
    Windows.GetModuleHandle('kernel32'), 'IsWow64Process'));
  if Assigned(IsWow64Process) then
  begin
    // Function is implemented: call it
    if not IsWow64Process(Windows.GetCurrentProcess,
IsWow64Result{%H-}) then
      raise SysUtils.Exception.Create('IsWindows64: bad process
handle');
    // Return result of function
    Result := IsWow64Result;
  end
  else
    // Function not implemented: can't be running on Wow64
    Result := False;
{$else} //if were running 64bit code, OS must be 64bit :)
begin
 Result := True;
{$endif}
end;

function RegReadString(pcKey_Path:pchar; pcValue_Name:Pchar;
hkRoot:hkey=HKEY_LOCAL_MACHINE):String;

var
  hkCurrent: HKEY;
  chrValue: array[0..512] of Char;
  dwLength: DWORD;
  intCode: integer;
  dwType:DWORD;
  strError: String;

begin
    //Tells RegQueryValueEx that we want a string value
    dwType := reg_SZ;

   // if the (32-bit) program is running on 64-bit Windows
   if isWin64 then
   begin
        try
            //opens the appropriate key
            //ask for the 64-bit registry path: KEY_WOW64_64KEY


            if RegOpenKeyEx( hkRoot ,pcKey_Path,0, KEY_QUERY_VALUE +
KEY_WOW64_64KEY, hkCurrent {%H-})=ERROR_SUCCESS then
             begin

                intCode:=RegQueryValueEx(hkCurrent, pcValue_Name, nil,
@dwType, @chrValue, @dwLength);

                if (intCode=ERROR_SUCCESS) then
                begin
                    result:=chrValue;
                end
                else
                begin
                    strError := 'There was an error detecting your
current registration information in the registry. The Error Code was:
'+IntToStr(intCode)+'.';
                    MessageDlg('Registry Error A', strError,
mtWarning, [mbOK], 0);

                end;
            end
            else
                begin
                    strError := 'There was an error loading your
current registration information from the registry. The Key Path:' +
strPas(pcKey_Path) + ' could not be opened.';
                    MessageDlg('Registry Error B', strError,
mtWarning, [mbOK], 0);
                end;

        except
            strError := 'There was an unknown error accessing the
registry. The Key Path:' + strPas(pcKey_Path) + ' or value ' +
strPas(pcValue_Name) + ' could not be opened.';
            MessageDlg('Registry Error C', strError, mtERROR,  [mbOK],
0);

       end;

   end
   // is 32-bit Windows
   else
   begin
        try


            //opens the appropriate key
            //ask for the 64-bit registry path: KEY_WOW64_64KEY
            if RegOpenKeyEx( hkRoot ,pcKey_Path,0, KEY_QUERY_VALUE,
hkCurrent )=ERROR_SUCCESS then
            begin

                intCode:=RegQueryValueEx(hkCurrent, pcValue_Name, nil,
@dwType, @chrValue, @dwLength);
                if (intCode=ERROR_SUCCESS) then
                begin
                    result:=chrValue;
                end
                else
                begin
                    strError := 'There was an error detecting your
current registration information in the registry. The Error Code was:
'+IntToStr(intCode)+'.';
                    MessageDlg('Registry Error A', strError,
mtWarning, [mbOK], 0);

                end;
            end
            else
                begin
                    strError := 'There was an error loading your
current registration information from the registry. The Key Path:' +
strPas(pcKey_Path) + ' could not be opened.';
                    MessageDlg('Registry Error B', strError,
mtWarning, [mbOK], 0);
                end;

        except
            strError := 'There was an unknown error accessing the
registry. The Key Path:' + strPas(pcKey_Path) + ' or value ' +
strPas(pcValue_Name) + ' could not be opened.';
            MessageDlg('Registry Error C', strError, mtERROR,  [mbOK],
0);

       end;
   end;

   //Closes the otherwise open access to the current registry key
   RegCloseKey(hkCurrent);



end;  

procedure RegWriteString(intParent_Key: integer; strPath: string;
strValue_Name: string; strValue: string);
var
  hkCurrent: HKEY;

begin
  // is 64-bit Windows
  if isWin64 then
  begin
     if RegOpenKeyEx(intParent_key, Pchar(strPath), 0, KEY_WRITE +
KEY_WOW64_64KEY, hkCurrent {%H-})  = ERROR_SUCCESS then
     begin
         RegSetValueEx(hkCurrent, pchar(strValue_Name), 0, REG_SZ,
PChar(strValue), Length(strValue) + 1); // The 1 is for the
terminating 0 (PChar)
    end;
  end
  // is 32-bit Windows
  else
  begin


    if RegOpenKeyEx( intParent_key,pchar(strPath),0, KEY_WRITE,
hkCurrent )  = ERROR_SUCCESS then
    begin
      RegSetValueEx(hkCurrent, pchar(strValue_Name), 0, REG_SZ,
PChar(strValue), Length(strValue) + 1); // The 1 is for the
terminating 0 (PChar)

    end;

  end;

  RegCloseKey(hkCurrent); // Close the open registry key


end;

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exdatis · 2012-08-30 05:21

Thanks!
Regards!

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u2o · 2014-12-17 05:02

@Christian: I used your code for some time, it really helped me in my
projects. However I would like to make a correction to solve a random
error.

Quote from: seier on August 30, 2012, 04:22:05 amCode:
[Select]intCode:=RegQueryValueEx(hkCurrent, pcValue_Name, nil,
@dwType, @chrValue, @dwLength);

Some times RegQueryValueEx return the error 234 (ERROR_MORE_DATA),
Although this does not always happen, it is very usual.

To prevent this from happening, you need to set a value to dwLength
before making the call.

For example:
Code: [Select]dwLength := SizeOf(dwLength);
intCode := RegQueryValueEx(hkCurrent, pcValue_Name, nil, @dwType,
@chrValue, @dwLength);

I hope to help as well. And although late thank you very much!