CATink_8h_source.html

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*/

#if !defined(__CATink_h__)

#define __CATink_h__


//=============================================================================

//  Includes

//=============================================================================


//  System Includes

#if !defined(__COREAUDIO_USE_FLAT_INCLUDES__)

    #include <CoreServices/CoreServices.h>

#else

    #include <CoreServices.h>

#endif


//=============================================================================

//  CATink

//

//  A Tink is a small jump island that can make one function appear as if it

//  has many addresses. Note that Tinks are not supported for 64 bit environments

//  as the APIs that made tinks useful have been replaced by APIs that do away

//  with all the reasons for using a tink.

//=============================================================================


template <class F>

class CATink

{


public:

    CATink(F proc) { Set(proc); }


    ~CATink() { Set((F)0xDEADDEAD); }       // jump to an obviously bad (odd) address if accessed after destruction


#if TARGET_CPU_PPC

    void Set(F proc)

    {

        /*

            lis     r11,0x1234

        00000000: 3D601234  lis        r11,4660

            ori     r11,r11,0x5678

        00000004: 616B5678  ori        r11,r11,$5678

            mtctr   r11

        00000008: 7D6903A6  mtctr      r11

            bctr

        0000000C: 4E800420  bctr

        */

        UInt32 p = UInt32(proc);

        mCode[0] = 0x3D600000 | (p >> 16);

        mCode[1] = 0x616B0000 | (p & 0xFFFF);

        mCode[2] = 0x7D6903A6;

        mCode[3] = 0x4E800420;

        MakeDataExecutable(mCode, sizeof(mCode));

    }


    operator F () { return F(mCode); }


private:

    UInt32      mCode[4];

#elif TARGET_CPU_X86

    void Set(F proc)

    {

        /*

            <tink>:   push   $0x12345678

            <tink+5>: ret

            <tink>:   0x34567868

            <tink+4>: 0x00e8c312

        */

        UInt32 p = UInt32(proc);

        mCode[0] = ((p & 0xFFFFFF) << 8) | 0x00000068;

        mCode[1] = 0xCCCCC300 | (p >> 24);

        MakeDataExecutable(mCode, sizeof(mCode));

    }


    operator F () { return F(&mCode[0]); }


private:

    UInt32      mCode[2];

#else

    #warning: CPU not directly supported by CATink


    // For other CPU's, just wrap the function pointer for now.

    // this bypasses what we're trying to accomplish with the Tink

    // (multiple unique "instances" of a function), but it will at

    // least compile and run.


    void Set(F proc) { mProcPtr = proc; }


    operator F () { return mProcPtr; }

private:

    F           mProcPtr;

#endif


//  Tinks cannot be allocated in STL Containers, so we make a few key methods private

private:

    CATink(){}

    CATink(const CATink&){}

    CATink& operator=(const CATink&){ return *this;}

};


#endif