C++ 读取 Windows 注册表值

// 读取 REG_SZ 类型键值的代码

HKEY  hKey       = NULL;
DWORD dwSize     = 0;
DWORD dwDataType = 0;
LPBYTE lpValue   = NULL;
LPCTSTR const lpValueName = _T("TcpPort");

LONG lRet = ::RegOpenKeyEx(HKEY_LOCAL_MACHINE,
   _T("SOFTWARE\\Microsoft\\MSSQLServer\\MSSQLServer\\SuperSocketNetLib\\Tcp"),
   0,
   KEY_QUERY_VALUE,
   &hKey);
if(ERROR_SUCCESS != lRet)
{
   // Error handling (see this FAQ)
   // return;
}
// Call once RegQueryValueEx to retrieve the necessary buffer size
::RegQueryValueEx(hKey, 
   lpValueName,
   0,
   &dwDataType,
   lpValue,  // NULL
   &dwSize); // will contain the data size

// Alloc the buffer
lpValue = (LPBYTE)malloc(dwSize);

// Call twice RegQueryValueEx to get the value
lRet = ::RegQueryValueEx(hKey, 
   lpValueName,
   0,
   &dwDataType,
   lpValue,
   &dwSize);
::RegCloseKey(hKey);
if(ERROR_SUCCESS != lRet)
{
   // Error handling
   // return;
}
// Enjoy of lpValue...
cout << "port ----------------------- " << lpValue << endl;

// free the buffer when no more necessary
free(lpValue);

// 此段代码来源：http://forums.codeguru.com/showthread.php?247020-Windows-SDK-Registry-How-can-I-read-data-from-the-registry&s=

// 读取 REG_DWORD 类型的注册表键值代码

long lRet;
HKEY hKey;
DWORD port;
DWORD dwType = REG_DWORD;
DWORD dwValue;
lRet = RegOpenKeyEx(
           HKEY_LOCAL_MACHINE,
           "SOFTWARE\\Microsoft\\MSSQLServer\\Client\\SuperSocketNetLib\\Tcp",
           0,
           KEY_QUERY_VALUE,
           &hKey
       );    //打开注册表
if(lRet == ERROR_SUCCESS)//读操作成功
{
    lRet = RegQueryValueEx(
               hKey,
               "DefaultPort",
               0,
               &dwType,
               (LPBYTE)&port,
               &dwValue
           );    //如果打开成功，则读
    if(lRet == ERROR_SUCCESS)
    {
        printf("\n打开成功，则读:");
        cout << "DefaultPort: " << port << endl;
        //mcfile << "DefaultPort: " << port << endl;
        mcfile << "<port>" << port << "</port>" << endl;
    }
    //以下是读取失败
    else
    {
        printf("\n读取失败:");
    }

}
//以下是打开失败
else
{
    printf("\n打开失败:");
}
RegCloseKey(hKey);//记住，一定要关闭

#include <winsock2.h>
#include <Windows.h>