Subversion Repositories FlightCtrl

#include "AP_Math.h"
#include <math.h>

// a varient of asin() that checks the input ranges and ensures a
// valid angle as output. If nan is given as input then zero is
// returned.
float safe_asin(float v)
{
        if (isnan(v)) {
                return 0.0;
        }
        if (v >= 1.0) {
                return M_PI/2;
        }
        if (v <= -1.0) {
                return -M_PI/2;
        }
        return asin(v);
}

// a varient of sqrt() that checks the input ranges and ensures a
// valid value as output. If a negative number is given then 0 is
// returned. The reasoning is that a negative number for sqrt() in our
// code is usually caused by small numerical rounding errors, so the
// real input should have been zero
float safe_sqrt(float v)
{
        float ret = sqrt(v);
        if (isnan(ret)) {
                return 0;
        }
        return ret;
}


// find a rotation that is the combination of two other
// rotations. This is used to allow us to add an overall board
// rotation to an existing rotation of a sensor such as the compass
// Note that this relies the set of rotations being complete. The
// optional 'found' parameter is for the test suite to ensure that it is.
enum Rotation rotation_combination(enum Rotation r1, enum Rotation r2, bool *found)
{
        Vector3f tv1, tv2;
        enum Rotation r;
        tv1(1,2,3);
        tv1.rotate(r1);
        tv1.rotate(r2);

        for (r=ROTATION_NONE; r<ROTATION_MAX;
             r = (enum Rotation)((uint8_t)r+1)) {
                Vector3f diff;
                tv2(1,2,3);
                tv2.rotate(r);
                diff = tv1 - tv2;
                if (diff.length() < 1.0e-6) {
                        // we found a match
                        if (found) {
                                *found = true;
                        }
                        return r;
                }
        }

        // we found no matching rotation. Someone has edited the
        // rotations list and broken its completeness property ...
        if (found) {
                *found = false;
        }
        return ROTATION_NONE;
}