Interface unit for sending debug messages to SysInternals ProcessMonitor

The latest version of SysInternals‘ excellent ProcessMonitor is now able to receive custom debug log messages and display them right in between the I/O logs.

Even though I still don’t quite get the rationale for the need to create a new API for this (in contrast to simply merging in the functionality of DebugView) I went straight ahead and converted the API to Delphi.

This should work with Delphi 6 and later. I successfully tested with Delphi 2007, 2009 and 2010.

(Update: the originally posted version did actually not work with Delphi 2007 or earlier because I had inexplicably overlooked “that Unicode thing”… Thanks to GunSmoker for pointing that out! Using $ifdef UNICODE and WideString is a cheap cop-out, I know – but it works)

Enjoy:

unit ProcMonDebugOutput;

interface

uses
  Windows;

type
  TProcessMonitorLogger = class
  private
    const
//      FILE_WRITE_ACCESS           = $00000002;
//      METHOD_BUFFERED             = $00000000;
//      FILE_DEVICE_PROCMON_LOG     = $00009535;
//      IOCTL_EXTERNAL_LOG_DEBUGOUT = CTL_CODE(FILE_DEVICE_PROCMON_LOG,
//                                             $81,
//                                             METHOD_BUFFERED,
//                                             FILE_WRITE_ACCESS);
      IOCTL_EXTERNAL_LOG_DEBUGOUT = $95358204;
    class var
      FDevice: THandle; // = INVALID_HANDLE_VALUE
    class function Open(): THandle;
    class procedure Close();
    {$IF CompilerVersion >= 21}
    class constructor Create;
    class destructor Destroy;
    {$IFEND}
  public
    class function Output(const AOutputString: {$ifdef UNICODE}String{$else}WideString{$endif}): Boolean;
  end;
  PML = TProcessMonitorLogger;

implementation

{ TProcessMonitorLogger }

//function CTL_CODE(const ADevType, AFunc, AMethod, AAccess: Cardinal): Cardinal; inline;
//begin
//  Result := (ADevType shl 16) or (AAccess shl 14) or (AFunc shl 2) or AMethod;
//end;

{$IF CompilerVersion >= 21}
class constructor TProcessMonitorLogger.Create;
begin
  FDevice := INVALID_HANDLE_VALUE;
end;

class destructor TProcessMonitorLogger.Destroy;
begin
  Close();
end;
{$IFEND}

class procedure TProcessMonitorLogger.Close;
begin
  if INVALID_HANDLE_VALUE <> FDevice then
    begin
      CloseHandle(FDevice);
      FDevice := INVALID_HANDLE_VALUE;
    end;
end;

class function TProcessMonitorLogger.Open(): THandle;
begin
  if INVALID_HANDLE_VALUE = FDevice then
    FDevice := CreateFile('\\.\Global\ProcmonDebugLogger',
                            GENERIC_READ or GENERIC_WRITE,
                            FILE_SHARE_READ or FILE_SHARE_WRITE or FILE_SHARE_DELETE,
                            nil,
                            OPEN_EXISTING,
                            FILE_ATTRIBUTE_NORMAL,
                            0);
  Result := FDevice;
end;

class function TProcessMonitorLogger.Output(const AOutputString: {$ifdef UNICODE}String{$else}WideString{$endif}): Boolean;
var
  lProcMonHwnd: THandle;
  lInputLength: Cardinal;
  lOutputLength: Cardinal;
  lLastError: Cardinal;
begin
  Result := False;
  if AOutputString = '' then
    SetLastError(ERROR_INVALID_PARAMETER)
  else
    begin
      lProcMonHwnd := Open();
      if lProcMonHwnd <> INVALID_HANDLE_VALUE then
        begin
          lInputLength := Length(AOutputString) * SizeOf(WideChar);
          lOutputLength := 0;
          Result := DeviceIoControl(lProcMonHwnd,
                                    IOCTL_EXTERNAL_LOG_DEBUGOUT,
                                    PWideChar(AOutputString),
                                    lInputLength,
                                    nil,
                                    0,
                                    lOutputLength,
                                    nil);
          if not Result then
            begin
              lLastError := GetLastError();
              if lLastError = ERROR_INVALID_PARAMETER then
                SetLastError(ERROR_WRITE_FAULT);
            end;
        end
      else
        SetLastError(ERROR_BAD_DRIVER);
    end;
end;

{$IF CompilerVersion < 21}
initialization
  TProcessMonitorLogger.FDevice := INVALID_HANDLE_VALUE;
finalization
  TProcessMonitorLogger.Close();
{$IFEND}
end.

Usage:

uses
  ProcMonDebugOutput;
begin
  PML.Output('How hard could it be?');
end;