fix24.cpp

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// $Id: fix24.cpp 1282 2006-06-09 09:46:49Z alex $
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 */


/*
*/ 

// Stardate 070494.10:25. Captain's Log - supplementary
// ====================================================
//
//      Pirated fixed16 code to base fixed24 upon
//      This was from revision 1.24 of fixed16.cpp
//                                                Jason



#include "camtypes.h"
//#include "fixed24.h" - in camtypes.h [AUTOMATICALLY REMOVED]
//#include "fix24.h" - in camtypes.h [AUTOMATICALLY REMOVED]



/********************************************************************************************

>   FIXED24 Fixed24Mul(FIXED24 arg1, FIXED24 arg2)

    Author:     Gavin_Theobald (Xara Group Ltd) <camelotdev@xara.com>
    Created:    15/6/2005
    Inputs:     two fixed24s
    Outputs:    None
    Returns:    FIXED24 result (arg1 * arg2)
    Scope:      Only to be used in the FIXED24 class.
    Purpose:    signed multiplication
    Errors:     None (no overflow checks). Rounds

********************************************************************************************/

fixed24 Fixed24Mul( fixed24 a, fixed24 b )
{
    fixed24             result;
    result.all = INT32((Int32x32To64(a.all,b.all)+0x800000)>>24) ;
    return result;
}

/********************************************************************************************

>   FIXED24 Fixed24Div(FIXED24 arg1, FIXED24 arg2)

    Author:     Gavin_Theobald (Xara Group Ltd) <camelotdev@xara.com>
    Created:    15/6/2005
    Inputs:     two fixed24s
    Outputs:    None
    Returns:    FIXED24 result (arg1 / arg2)
    Scope:      Only to be used in the FIXED24 class.
    Purpose:    signed division
    Errors:     None (no overflow checks). No rounding either (should it?)
            Overflow will cause a DIV0 exception, as will divide by zero

Note that this is not very efficient as it forces a multiply that
could instead be performed by a shift. The alternative is to use
int64s but this would then compile as a 64bit/64bit division which
is worse.

Why isn't there a Int64div32to32 function?

********************************************************************************************/

fixed24 Fixed24Div(fixed24 a,fixed24 b)
{
    fixed24 result ;
    result.all = MulDiv(a.all,1<<24,b.all) ;
    return result ;
}

/********************************************************************************************

>   double Fixed24ToDouble( FIXED24 arg )

    Author:     Gavin_Theobald (Xara Group Ltd) <camelotdev@xara.com>
    Created:    15/6/2005
    Inputs:     FIXED24 argument
    Outputs:    None
    Returns:    double-precision value
    Scope:      Only to be used in the FIXED24 class.
    Purpose:    General type conversion
    Errors:     None

This code relies on the compiler efficiently replacing the division by a multiplication
of the reciprical.

********************************************************************************************/

double Fixed24ToDouble( fixed24 a )
{
    return (double)a.all/(1<<24) ;
}

/********************************************************************************************

>   fixed24 DoubleToFixed24( double arg )

    Author:     Gavin_Theobald (Xara Group Ltd) <camelotdev@xara.com>
    Created:    15/6/2005
    Inputs:     double-precision argument
    Outputs:    None
    Returns:    FIXED24 value
    Purpose:    General type conversion
    Errors:     None (overflow will cause exception)

********************************************************************************************/

fixed24 DoubleToFixed24( double arg )
{
    fixed24 result ;
#if 0 //defined(_M_IX86)
    //
    // This avoids the slow fix operation. Add a large number so that
    // the double always has the same exponent and the mantissa becomes,
    // in affect, a fixed point value with the value we want in the
    // bottom 32 bits.
    //
    // Note that we are relying on the compiler to convert this to
    // efficient code.
    //
    // TODO: Test!
    //
    static const double fFix = (XLONG)3<<(DBL_MANT_DIG-24-2);
    double F = arg+fFix;
    result.all = (INT32&)F ;
#else
    result.all = INT32(arg*(1<<24)) ;
#endif
    return result ;
}

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