Hi all,

The other day I had to develop a small C++ sample which shows how to readthe list of values of a REG_MULTI_SZ from the registry, and add a new value just after one of the values of the list. Additionally,I used methods and constants from tchar.h extensively, so it didn't matter if I compiled the code as UNICODE or ANSI. Here is the code:

#include "windows.h"

#include "tchar.h"

#include "conio.h"

#include "stdio.h"

#define MY_KEY _T("PathToMyRegistryKey\\MyRegistryKey") // Registry key

#define MY_VALUES _T("NameOfTheREG_MULTI_SZListOfValues") // Registry values

#define NEW_VALUE _T("MyNewValue") // New value

#define FIND_VALUE _T("AnExistingValue") // We will insert the new value after this one
int _tmain(int argc, _TCHAR* argv[])

{

	LONG lResult = 0;

	HKEY hKey = NULL;

	LPTSTR lpValues = NULL;

	LPTSTR lpValue = NULL;

	LPTSTR lpNewValues = NULL;

	LPTSTR lpNewValue = NULL;

	DWORD cbValues = 0;

	DWORD cbNewValues = 0;

	DWORD cbNewValue = 0;

	BOOL bFound = FALSE;
	__try

	{

		// OPEN THE REGISTRY KEY

		//

		_tprintf(_T("RegOpenKeyEx..."));

		lResult = RegOpenKeyEx(

			HKEY_LOCAL_MACHINE,

			MY_KEY,

			0,

			KEY_ALL_ACCESS,

			&hKey

		);

		if (ERROR_SUCCESS != lResult) { _tprintf(_T("ERROR 0x%x\n"), lResult); return 1; }

		_tprintf(_T("SUCCESS\n"));
		// READ THE REG_MULTI_SZ VALUES

		//

		// Get size of the buffer for the values

		_tprintf(_T("RegQueryValueEx..."));

		lResult = RegQueryValueEx(

			hKey,

			MY_VALUES,

			NULL,

			NULL,

			NULL,

			&cbValues

		);

		if (ERROR_SUCCESS != lResult) { _tprintf(_T("ERROR 0x%x\n"), lResult); return 1; }

		_tprintf(_T("SUCCESS\n"));
		// Allocate the buffer

		_tprintf(_T("malloc..."));

		lpValues = (LPTSTR)malloc(cbValues);

		if (NULL == lpValues) { _tprintf(_T("ERROR 0x%x\n"), GetLastError()); return 1; }

		_tprintf(_T("SUCCESS\n"));
		// Get the values

		_tprintf(_T("RegQueryValueEx..."));

		lResult = RegQueryValueEx(

			hKey,

			MY_VALUES,

			NULL,

			NULL,

			(LPBYTE)lpValues,

			&cbValues

		);

		if (ERROR_SUCCESS != lResult) { _tprintf(_T("ERROR 0x%x\n"), lResult); return 1; }

		_tprintf(_T("SUCCESS\n"));
		// SHOW THE VALUES

		//

		_tprintf(_T("\n**************************\n"));

		_tprintf(_T("OLD VALUES\n"));

		_tprintf(_T("**************************\n\n"));

		lpValue = lpValues;

		for (; '\0' != *lpValue; lpValue += _tcslen(lpValue) + 1)

		{

			// Show one value

			_tprintf(_T("%s\n"), lpValue);

		}

		_tprintf(_T("\n**************************\n\n"));
		// INSERT A NEW VALUE AFTER A SPECIFIC VALUE IN THE LIST OF VALUES

		//

		// Allocate a new buffer for the old values plus the new one

		_tprintf(_T("malloc..."));

		cbNewValue = (_tcslen(NEW_VALUE) + 1) * sizeof(TCHAR);

		cbNewValues = cbValues + cbNewValue;

		lpNewValues = (LPTSTR)malloc(cbNewValues);

		if (NULL == lpNewValues) { _tprintf(_T("ERROR 0x%x\n"), GetLastError()); return 1; }

		_tprintf(_T("SUCCESS\n"));		
		// Find the value after which we will insert the new one

		lpValue = lpValues;

		lpNewValue = lpNewValues;

		bFound = FALSE;

		for (; '\0' != *lpValue; lpValue += _tcslen(lpValue) + 1)

		{

			// Copy the current value to the target buffer

			memcpy(lpNewValue, lpValue, (_tcslen(lpValue) + 1) * sizeof(TCHAR));
			if (0 == _tcscmp(lpValue, FIND_VALUE))

			{

				// The current value is the one we wanted to find

				bFound = TRUE;
				// Copy the new value to the target buffer

				lpNewValue += _tcslen(lpValue) + 1;

				memcpy(lpNewValue, NEW_VALUE, (_tcslen(NEW_VALUE) + 1) * sizeof(TCHAR));

				lpNewValue += _tcslen(NEW_VALUE) + 1;

			}

			else

			{

				// This is not the value we want, continue to the next one

				lpNewValue += _tcslen(lpValue) + 1;

			}

		}

		if (!bFound)

		{

			// We didn't find the value we wanted. Insert the new value at the end

			memcpy(lpNewValue, NEW_VALUE, (_tcslen(NEW_VALUE) + 1) * sizeof(TCHAR));

			lpNewValue += _tcslen(NEW_VALUE) + 1;

		}

		*lpNewValue = *lpValue;
		// SHOW THE NEW VALUES

		//

		_tprintf(_T("\n**************************\n"));

		_tprintf(_T("NEW VALUES\n"));

		_tprintf(_T("**************************\n\n"));

		lpNewValue = lpNewValues;

		for (; '\0' != *lpNewValue; lpNewValue += _tcslen(lpNewValue) + 1)

		{

			// Show one value

			_tprintf(_T("%s\n"), lpNewValue);

		}

		_tprintf(_T("\n**************************\n\n"));
		// WRITE THE NEW VALUES BACK TO THE KEY

		//

		_tprintf(_T("RegSetValueEx..."));

		lResult = RegSetValueEx(

			hKey,

			MY_VALUES,

			NULL,

			REG_MULTI_SZ,

			(LPBYTE)lpNewValues,

			cbNewValues

		);

		if (ERROR_SUCCESS != lResult) { _tprintf(_T("ERROR 0x%x\n"), lResult); return 1; }

		_tprintf(_T("SUCCESS\n"));

	}

	__finally

	{

		// Clean up

		//

		if (NULL != lpValues) { free(lpValues); }

		if (NULL != lpNewValues) { free(lpNewValues); }

		if (NULL != hKey) { RegCloseKey(hKey); }
		//_tprintf(_T("\n<<PRESS ANY KEY>>\n"));

		//_getch();

	}
	return 0;

}

Regards,

Alex (Alejandro Campos Magencio)