Question

What’s the simplest way to read a registry key value to std::String?

Say I’ve got :

HKEY_LOCAL_MACHINE / SOFTWARE / MyApp / value1 = "some text"
HKEY_LOCAL_MACHINE / SOFTWARE / MyApp / value2 = "some more text"

How do I get those values to std::string in a fast way ?

Answer 1

I have some very old code, but it should give you a good idea:

/**
* @param location The location of the registry key. For example "Software\\Bethesda Softworks\\Morrowind"
* @param name the name of the registry key, for example "Installed Path"
* @return the value of the key or an empty string if an error occured.
*/
std::string getRegKey(const std::string& location, const std::string& name){
    HKEY key;
    TCHAR value[1024]; 
    DWORD bufLen = 1024*sizeof(TCHAR);
    long ret;
    ret = RegOpenKeyExA(HKEY_LOCAL_MACHINE, location.c_str(), 0, KEY_QUERY_VALUE, &key);
    if( ret != ERROR_SUCCESS ){
        return std::string();
    }
    ret = RegQueryValueExA(key, name.c_str(), 0, 0, (LPBYTE) value, &bufLen);
    RegCloseKey(key);
    if ( (ret != ERROR_SUCCESS) || (bufLen > 1024*sizeof(TCHAR)) ){
        return std::string();
    }
    std::string stringValue = std::string(value, (size_t)bufLen - 1);
    size_t i = stringValue.length();
    while( i > 0 && stringValue[i-1] == '\0' ){
        --i;
    }
    return stringValue.substr(0,i); 
}