Fixed point MOD (for sin LUT)

Hello all,

I have a fixed-point function (16.16) that calculates SIN and COS from a lookup table. However, since the LUT is in the range 0-360 (degrees), how do I convert an arbitrary angle (e.g. 535.2) to the range 0-360.

Usually a simple MOD would do it:

Code:

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angle2 = angle % 360;

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However in fixed point, you can't just do that, so a way to do it is:

Code:

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angle2 = angle - fixmul(fixfloor(fixdiv( angle,360 )),360);
// same as (floating point):
angle2 = angle - ( floor( angle/360 ) * 360 );

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But surely there is a faster way?

EDIT: Here is the whole function which looks up sin in a LUT which has one value for each degree, then does linear interpolation for partial degrees (e.g. 120.75 degrees).

Code:

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fixed fixsin(fixed x){
        int a, b;
        fixed c, d, val;
        // First ensure value is 0-360 (not including 360)
        x = x - itofix(fixfloor(fixdiv( x,FIX360 )) * 360);
        if (x<0){ x=-x; }
        // Get the index directly before and after point
        a = fixfloor(x);
        b = a+1;
        if (b>359){ b=0; }
        // Get the sin values directly before and after point
        c = _sin_lut[ a ];
        d = _sin_lut[ b ];
        // Do linear interpolation to get actual value
        return c + fixmul((d-c),(x-itofix( a )));
}

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