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c++visual-c++c++11crypto++

Using typedef ClassName< > after class

I'm new in C++ world and I don't understand what's going on when using this structure :

template <typename T>
   class NameClass{
.........

};
typedef NameClass<CryptoPP::AES> CryptAES;
//!Typedef for the AES Encryption\Decryption
typedef NameClass<CryptoPP::Blowfish> CryptBlowFish;
//!Typedef for BlowFish Encryption\Decryption

Is there an explanation?

Solution

  • There is very likely also

    template< classT > or template <typename T> above class NameClass and this means NameClass is a template, parametrised by the type of encryption it uses, by T.

    read about templates here.

    typedef is a keyword in C++. It's purpose is to abbreviate complexed names. In your example

    NameClass<CryptoPP::Blowfish>

    can be used by a shorthand of CryptBlowFish

    because it was typedefed as 

    typedef NameClass<CryptoPP::Blowfish> CryptBlowFish;

    before. So

    CryptBlowFish cbf;

    is same as 

    NameClass<CryptoPP::Blowfish> cbf;

    http://en.wikipedia.org/wiki/Typedef