Compile-time polymorphism of "interfaces"

From:
Andrew Schweitzer <anschweitzer@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Wed, 18 Jul 2007 13:13:45 CST
Message-ID:
<1184779677.825263.293980@g12g2000prg.googlegroups.com>
Compile-time polymorphism newbie question here. We are using virtual
functions and getting a performance hit in a device driver. Can some
suggest a way to implement this with templates? We don't actually need
run-time polymorphism, but we do want to share a bunch of code at
compile time.

class IInterface1{public: virtual void DoSomething() = 0;};

class IInterface2{public: virtual void DoSomethingElse() = 0;};

class Dervied1 : public virtual IInterface1{
    int m_i;
    IInterface2* m_pII2;
public:
    virtual void DoSomething() {m_i++;}
    void UseInterface(){m_pII2->DoSomethingElse();}
}

class Dervied1v2 : public virtual IInterface1{
    int m_i;
    IInterface2* m_pII2;
public:
    virtual void DoSomething() {m_i++;}
    void UseInterface(){m_pII2->DoSomethingElse();}
}

class Dervied2 : public virtual IInterface1{
    int m_i;
    IInterface1* m_pII1; //Might be a Derived1 or a Derived1v2, but it
would be nice
                                //to figure out at compile time and
get rid of virtual.
public:
    virtual void DoSomethingElse() {m_i++;}
    void UseInterface(){m_pII2->DoSomething();}
}

The ways I thought of to do this with templates all seemed to have
circular definitions.

Thanks,

Andy

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