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Understanding The COM Single-Threaded Apartment Part 1

, 6 Jan 2005 CPOL
Learn the fundamental principles of the COM Single-Threaded Apartment Model by code examples.
ccomthread_src.zip
LegacyCOMObject1
Shared
SimpleCOMObject1
SimpleCOMObject2
Test Programs
LegacyCOMObject1.def
LegacyCOMObject1.dsp
LegacyCOMObject1.dsw
LegacyCOMObject1.rgs
LegacyCOMObject1.tlb
LegacyCOMObject1ps.def
LegacyCOMObject1ps.mk
SimpleCOMObject1.def
SimpleCOMObject1.dsp
SimpleCOMObject1.dsw
SimpleCOMObject1.rgs
SimpleCOMObject1.tlb
SimpleCOMObject1ps.def
SimpleCOMObject1ps.mk
SimpleCOMObject2.def
SimpleCOMObject2.dsp
SimpleCOMObject2.dsw
SimpleCOMObject2.rgs
SimpleCOMObject2.tlb
SimpleCOMObject2ps.def
SimpleCOMObject2ps.mk
VBTest
VCTests
FormMain.frm
MSSCCPRJ.SCC
VBTest.exe
VBTest.vbp
VBTest.vbw
DemonstrateDefaultSTA
DemonstrateExeServerSTA
DemonstrateLegacySTA
DemonstrateNoMessageLoop
DemonstrateSTA
VCTest01
VCTest02
SimpleCOMObject2.tlh
SimpleCOMObject2.tli
VCTest01.dsp
VCTest01.dsw
SimpleCOMObject2.tlh
SimpleCOMObject2.tli
VCTest02.dsp
VCTest02.dsw
Client
Implementation
Interface
VCTest01
VCTest01.dsp
VCTest01.dsw
ExeServerImpl
ExeServerImpl.dsp
ExeServerImpl.dsw
ExeServerInterfaces
ExeObj01.rgs
ExeObj02.rgs
ExeObj03.rgs
ExeServerInterfaces.def
ExeServerInterfaces.dsp
ExeServerInterfaces.dsw
ExeServerInterfaces.tlb
ExeServerInterfacesps.def
ExeServerInterfacesps.mk
VCTest01
VCTest02
LegacyCOMObject1.tlh
LegacyCOMObject1.tli
VCTest01.dsp
VCTest01.dsw
VCTest02.dsp
VCTest02.dsw
VCTest01
SimpleCOMObject2.tlh
SimpleCOMObject2.tli
VCTest01.dsp
VCTest01.dsw
VCTest01
SimpleCOMObject2.tlh
SimpleCOMObject2.tli
VCTest01.dsp
VCTest01.dsw
//
// Registry.cpp
//

#include <objbase.h>
#include <assert.h>

#include "Registry.h"

////////////////////////////////////////////////////////
//
// Internal helper functions prototypes
//

// Set the given key and its value.
BOOL setKeyAndValue(const char* pszPath,
                    const char* szSubkey,
                    const char* szValue) ;

// Convert a CLSID into a char string.
void CLSIDtochar(const CLSID& clsid, 
                 char* szCLSID,
                 int length) ;

// Determine if a particular subkey exists.
BOOL SubkeyExists(const char* pszPath,
                  const char* szSubkey) ;

// Delete szKeyChild and all of its descendents.
LONG recursiveDeleteKey(HKEY hKeyParent, const char* szKeyChild) ;

////////////////////////////////////////////////////////
//
// Constants
//

// Size of a CLSID as a string
const int CLSID_STRING_SIZE = 39 ;

/////////////////////////////////////////////////////////
//
// Public function implementation
//

//
// Register the component in the registry.
//
HRESULT RegisterServer(HMODULE hModule,            // DLL module handle
                       const CLSID& clsid,         // Class ID
                       const char* szFriendlyName, // Friendly Name
                       const char* szVerIndProgID, // Programmatic
                       const char* szProgID)       //   IDs
{
	// Get server location.
	char szModule[512] ;
	DWORD dwResult =
		::GetModuleFileName(hModule, 
		                    szModule,
		                    sizeof(szModule)/sizeof(char)) ;
	assert(dwResult != 0) ;

	// Convert the CLSID into a char.
	char szCLSID[CLSID_STRING_SIZE] ;
	CLSIDtochar(clsid, szCLSID, sizeof(szCLSID)) ;

	// Build the key CLSID\\{...}
	char szKey[64] ;
	strcpy(szKey, "CLSID\\") ;
	strcat(szKey, szCLSID) ;
  
	// Add the CLSID to the registry.
	setKeyAndValue(szKey, NULL, szFriendlyName) ;

	// Add the server filename subkey under the CLSID key.
#ifdef _OUTPROC_SERVER_
	setKeyAndValue(szKey, "LocalServer32", szModule) ;
#else
	setKeyAndValue(szKey, "InprocServer32", szModule) ;
#endif

	// Add the ProgID subkey under the CLSID key.
	setKeyAndValue(szKey, "ProgID", szProgID) ;

	// Add the version-independent ProgID subkey under CLSID key.
	setKeyAndValue(szKey, "VersionIndependentProgID",
	               szVerIndProgID) ;

	// Add the version-independent ProgID subkey under HKEY_CLASSES_ROOT.
	setKeyAndValue(szVerIndProgID, NULL, szFriendlyName) ; 
	setKeyAndValue(szVerIndProgID, "CLSID", szCLSID) ;
	setKeyAndValue(szVerIndProgID, "CurVer", szProgID) ;

	// Add the versioned ProgID subkey under HKEY_CLASSES_ROOT.
	setKeyAndValue(szProgID, NULL, szFriendlyName) ; 
	setKeyAndValue(szProgID, "CLSID", szCLSID) ;

	return S_OK ;
}

//
// Remove the component from the registry.
//
LONG UnregisterServer(const CLSID& clsid,         // Class ID
                      const char* szVerIndProgID, // Programmatic
                      const char* szProgID)       //   IDs
{
	// Convert the CLSID into a char.
	char szCLSID[CLSID_STRING_SIZE] ;
	CLSIDtochar(clsid, szCLSID, sizeof(szCLSID)) ;

	// Build the key CLSID\\{...}
	char szKey[80] ;
	strcpy(szKey, "CLSID\\") ;
	strcat(szKey, szCLSID) ;

	// Check for a another server for this component.
#ifdef _OUTPROC_SERVER_
	if (SubkeyExists(szKey, "InprocServer32"))
#else
	if (SubkeyExists(szKey, "LocalServer32"))
#endif
	{
		// Delete only the path for this server.
#ifdef _OUTPROC_SERVER_
		strcat(szKey, "\\LocalServer32") ;
#else
		strcat(szKey, "\\InprocServer32") ;
#endif
		LONG lResult = recursiveDeleteKey(HKEY_CLASSES_ROOT, szKey) ;
		assert(lResult == ERROR_SUCCESS) ;
	}
	else
	{
		// Delete all related keys.
		// Delete the CLSID Key - CLSID\{...}
		LONG lResult = recursiveDeleteKey(HKEY_CLASSES_ROOT, szKey) ;
		assert((lResult == ERROR_SUCCESS) ||
		       (lResult == ERROR_FILE_NOT_FOUND)) ; // Subkey may not exist.

		// Delete the version-independent ProgID Key.
		lResult = recursiveDeleteKey(HKEY_CLASSES_ROOT, szVerIndProgID) ;
		assert((lResult == ERROR_SUCCESS) ||
		       (lResult == ERROR_FILE_NOT_FOUND)) ; // Subkey may not exist.

		// Delete the ProgID key.
		lResult = recursiveDeleteKey(HKEY_CLASSES_ROOT, szProgID) ;
		assert((lResult == ERROR_SUCCESS) ||
		       (lResult == ERROR_FILE_NOT_FOUND)) ; // Subkey may not exist.
	}
	return S_OK ;
}

///////////////////////////////////////////////////////////
//
// Internal helper functions
//

// Convert a CLSID to a char string.
void CLSIDtochar(const CLSID& clsid,
                 char* szCLSID,
                 int length)
{
	assert(length >= CLSID_STRING_SIZE) ;
	// Get CLSID
	LPOLESTR wszCLSID = NULL ;
	HRESULT hr = StringFromCLSID(clsid, &wszCLSID) ;
	assert(SUCCEEDED(hr)) ;

	// Covert from wide characters to non-wide.
	wcstombs(szCLSID, wszCLSID, length) ;

	// Free memory.
	CoTaskMemFree(wszCLSID) ;
}

//
// Delete a key and all of its descendents.
//
LONG recursiveDeleteKey(HKEY hKeyParent,           // Parent of key to delete
                        const char* lpszKeyChild)  // Key to delete
{
	// Open the child.
	HKEY hKeyChild ;
	LONG lRes = RegOpenKeyEx(hKeyParent, lpszKeyChild, 0,
	                         KEY_ALL_ACCESS, &hKeyChild) ;
	if (lRes != ERROR_SUCCESS)
	{
		return lRes ;
	}

	// Enumerate all of the decendents of this child.
	FILETIME time ;
	char szBuffer[256] ;
	DWORD dwSize = 256 ;
	while (RegEnumKeyEx(hKeyChild, 0, szBuffer, &dwSize, NULL,
	                    NULL, NULL, &time) == S_OK)
	{
		// Delete the decendents of this child.
		lRes = recursiveDeleteKey(hKeyChild, szBuffer) ;
		if (lRes != ERROR_SUCCESS)
		{
			// Cleanup before exiting.
			RegCloseKey(hKeyChild) ;
			return lRes;
		}
		dwSize = 256 ;
	}

	// Close the child.
	RegCloseKey(hKeyChild) ;

	// Delete this child.
	return RegDeleteKey(hKeyParent, lpszKeyChild) ;
}

//
// Determine if a particular subkey exists.
//
BOOL SubkeyExists(const char* pszPath,    // Path of key to check
                  const char* szSubkey)   // Key to check
{
	HKEY hKey ;
	char szKeyBuf[80] ;

	// Copy keyname into buffer.
	strcpy(szKeyBuf, pszPath) ;

	// Add subkey name to buffer.
	if (szSubkey != NULL)
	{
		strcat(szKeyBuf, "\\") ;
		strcat(szKeyBuf, szSubkey ) ;
	}

	// Determine if key exists by trying to open it.
	LONG lResult = ::RegOpenKeyEx(HKEY_CLASSES_ROOT, 
	                              szKeyBuf,
	                              0,
	                              KEY_ALL_ACCESS,
	                              &hKey) ;
	if (lResult == ERROR_SUCCESS)
	{
		RegCloseKey(hKey) ;
		return TRUE ;
	}
	return FALSE ;
}

//
// Create a key and set its value.
//   - This helper function was borrowed and modifed from
//     Kraig Brockschmidt's book Inside OLE.
//
BOOL setKeyAndValue(const char* szKey,
                    const char* szSubkey,
                    const char* szValue)
{
	HKEY hKey;
	char szKeyBuf[1024] ;

	// Copy keyname into buffer.
	strcpy(szKeyBuf, szKey) ;

	// Add subkey name to buffer.
	if (szSubkey != NULL)
	{
		strcat(szKeyBuf, "\\") ;
		strcat(szKeyBuf, szSubkey ) ;
	}

	// Create and open key and subkey.
	long lResult = RegCreateKeyEx(HKEY_CLASSES_ROOT ,
	                              szKeyBuf, 
	                              0, NULL, REG_OPTION_NON_VOLATILE,
	                              KEY_ALL_ACCESS, NULL, 
	                              &hKey, NULL) ;
	if (lResult != ERROR_SUCCESS)
	{
		return FALSE ;
	}

	// Set the Value.
	if (szValue != NULL)
	{
		RegSetValueEx(hKey, NULL, 0, REG_SZ, 
		              (BYTE *)szValue, 
		              strlen(szValue)+1) ;
	}

	RegCloseKey(hKey) ;
	return TRUE ;
}

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About the Author

Lim Bio Liong
Web Developer
Singapore Singapore
Lim Bio Liong is a Specialist at a leading Software House in Singapore.
 
Bio has been in software development for over 10 years. He specialises in C/C++ programming and Windows software development.
 
Bio has also done device-driver development and enjoys low-level programming. Bio has recently picked up C# programming and has been researching in this area.

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