So you think you know many programming languages?

Take  a look at this website http://www.roesler-ac.de/wolfram/hello.htm which exhibits around 330 “Hello World” programs in different programming languages!

Have you ever wondered how threads work and how they achieve “parallel” execution?
I have written a small demonstration article and posted it on CodeProject: “Threads” without threads

Check it out and rate my article!

Hello

I’ve been looking around and was surprised that there will be a new C++ standard and additions dubbed “C++0x”.

According to Bjarne Stroustrup, “the new standard will be almost 100% compatible with the current standard”.

Some of the features I like about this new addition are:
- atomic keyword (for uninterruptible code)
- thread local storage
- asynchronous calls through the “future” keyword
- implicit function calls (as if using properties in other languages)
- parallel execution

The good news for some, probably bad news for eager ones is that the C++ Standards Committee aims to introduce the new standard in 2009.

Reference:

• http://en.wikipedia.org/wiki/C++0x
• The design of C++0x

Introduction

A while ago I wrote a small utility that converts DOT syntax into an image using
the WinGraphViz.DLL COM component.

However it is not very usual to have the user register this component before
running the tool, thus I started looking around for a way to use COM component
as if they were normal DLL.
The research yielded that there are many techniques to accomplish that:

1. Registration-Free COM (for XP and above)
2. Emulating the CoCreateInstance()

To learn more about the Registration-Free COM please check the references at
the end of this article.

Emulating CoCreateInstance()

Normally, to create an instance you would do something like:

  hr = CoCreateInstance(CLSID_DOT, NULL, CLSCTX_ALL,
  IID_IDOT, (LPVOID *)&pIDOT);

This will cause OLE to fetch the associated DLL from the registry and call its
DllGetClassObject() method to get a class factory then from the class factory
an instance of your required IID will be created.

For that reason we may emulate the CoCreateInstance() by the following code:

HRESULT __stdcall MyCoCreateInstance(
  LPCTSTR szDllName,
  IN REFCLSID rclsid,
  IUnknown* pUnkOuter,
  IN REFIID riid,
  OUT LPVOID FAR* ppv)
{
  HRESULT hr = REGDB_E_KEYMISSING;

  HMODULE hDll = ::LoadLibrary(szDllName);
  if (hDll == 0)
    return hr;

  typedef HRESULT (__stdcall *pDllGetClassObject)(IN REFCLSID rclsid, IN REFIID riid, OUT LPVOID FAR* ppv);

  pDllGetClassObject GetClassObject = (pDllGetClassObject)::GetProcAddress(hDll, "DllGetClassObject");
  if (GetClassObject == 0)
  {
    ::FreeLibrary(hDll);
    return hr;
  }

  IClassFactory *pIFactory;

  hr = GetClassObject(rclsid, IID_IClassFactory, (LPVOID *)&pIFactory);

  if (!SUCCEEDED(hr))
    return hr;

  hr = pIFactory->CreateInstance(pUnkOuter, riid, ppv);
  pIFactory->Release();

  return hr;
}

Notice that how this function takes a parameter holding the DLL’s name.

Using the code

You need your application to run first if the COM is registered, if not you
would resort to emulating the CoCreateInstance(). Your code could look like
this:

hr = CoCreateInstance(CLSID_DOT, NULL, CLSCTX_ALL,
  IID_IDOT, (LPVOID *)&pIDOT);

if (hr == REGDB_E_CLASSNOTREG)
{
  hr = MyCoCreateInstance(_T("WinGraphViz.dll"), CLSID_DOT, NULL, IID_IDOT, (LPVOID *)&pIDOT);
}

if (FAILED(hr))
{
  cout << "CoCreateInstance Failed: " << hr << "nn";
  return -1;
}

Reference

The following links were helpful during the building of this simple snippet:

• Mikhail Arkhipov WebLog: Registration-free COM
  http://blogs.msdn.com/mikhailarkhipov/archive/2005/04/01/404433.aspx
• Dave Templin: Simplify App Deployment with ClickOnce and Registration-Free
  COM
  http://msdn.microsoft.com//msdnmag/issues/05/04/RegFreeCOM/default.aspx
  
• Jeff Glatt: COM in Plain C
  http://www.codeproject.com/com/com_in_c1.asp
• Registration-Free Activation of COM Components: A Walkthrough
  http://msdn2.microsoft.com/en-us/library/ms973913.aspx