Registry RegQueryValueExW - c++

Question

Is it possible to read a value in the Registry not to an array of chars but directly to an AnsiString in this case?
LONG result;
wchar_t buf[255] = {0};
DWORD dwBufSize = sizeof(buf);
String d = "Nazwa";
DWORD dwType = REG_SZ;
result = ::RegQueryValueExW( hkSoftware, (LPCWSTR)(d.c_str()), NULL, &dwType, (LPBYTE)&buf, &dwBufSize );

Answer 1

First off, your code example is not using AnsiString. In C++Builder 2009 and later, String is an alias for UnicodeString instead.
And yes, you can use UnicodeString with RegQueryValueExW(), without using a typecast. UnicodeString::c_str() returns a WideChar*, and WideChar is an alias for wchar_t on Windows, so WideChar* (aka wchar_t *) is implicitly convertible to LPCWSTR (aka const wchar_t *), eg:
LONG result;
wchar_t buf[255] = {0};
DWORD dwBufSize = sizeof(buf);
UnicodeString d = L"Nazwa";
DWORD dwType = REG_SZ;
result = ::RegQueryValueExW( hkSoftware, d.c_str(), NULL, &dwType, reinterpret_cast<LPBYTE>(&buf), &dwBufSize );
You can also use UnicodeString as a buffer to receive string data from RegQueryValueExW(), eg:
LONG result;
UnicodeString buf;
buf.SetLength(...);
DWORD dwBufSize = ByteLength(buf);
UnicodeString d = L"Nazwa";
DWORD dwType = REG_SZ;
result = ::RegQueryValueExW( hkSoftware, d.c_str(), NULL, &dwType, reinterpret_cast<LPBYTE>(buf.c_str()), &dwBufSize );
if ( result == 0 ) {
buf.SetLength(dwBufSize/sizeof(WideChar));
...
}
That being said, you should consider using C++Builder's TRegistry class instead of using the Win32 Registry API directly. TRegistry has many methods for reading different kinds of data, including ReadString() for String data, eg:
#include <Registry.hpp>
TRegistry *Reg = new TRegistry;
String buf;
Reg->RootKey = ...;
if (Reg->OpenKeyReadOnly(_D("...")))
{
buf = Reg->ReadString(_D("Nazwa"));
Reg->CloseKey();
}
delete Reg;