[C++] Windows Registry Key

Example

int nRet;
HKEY hKey;
DWORD dwSize = 256;  // Note 1
char pszKeyName[256] = {0};

nRet = RegOpenKeyEx(HKEY_LOCAL_MACHINE,"Software\\PathA",0,KEY_READ,&hKey);
if (nRet == ERROR_SUCCESS)
    nRet = RegQueryValueEx(hKey,"KeyName",NULL,NULL,(BYTE *)g_pszKeyName,&dwSize);
nRet = RegCloseKey(hKey); // Note 2

dwSize = 256; // Note 3

nRet = RegOpenKeyEx(HKEY_LOCAL_MACHINE,"Software\\PathB",0,KEY_READ,&hKey);
if(nRet == ERROR_SUCCESS)
    nRet = RegQueryValueEx(hKey,"KeyName",NULL,NULL,(BYTE *)g_pszKeyName,&dwSize);
nRet = RegCloseKey(hKey);

Note

• Note 1: dwSize 和 pszKeyName[]要夠大.
• Note 2: RegOpenKeyEx後要記得RegCloseKey, 不然RegOpenKeyEx 65535次會無法RegOpenKeyEx.
• Note 3: 重複使用dwSize 要reset size不然dwSize會為之前RegQueryValueEx的值.

References

• RegOpenKeyEx
• RegQueryValueEx
• RegCloseKey