Spline.h

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#ifndef SimTK_SIMMATH_SPLINE_H_
#define SimTK_SIMMATH_SPLINE_H_

/* -------------------------------------------------------------------------- *
 *                        Simbody(tm): SimTKmath                              *
 * -------------------------------------------------------------------------- *
 * This is part of the SimTK biosimulation toolkit originating from           *
 * Simbios, the NIH National Center for Physics-Based Simulation of           *
 * Biological Structures at Stanford, funded under the NIH Roadmap for        *
 * Medical Research, grant U54 GM072970. See https://simtk.org/home/simbody.  *
 *                                                                            *
 * Portions copyright (c) 2008-13 Stanford University and the Authors.        *
 * Authors: Peter Eastman                                                     *
 * Contributors: Michael Sherman                                              *
 *                                                                            *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may    *
 * not use this file except in compliance with the License. You may obtain a  *
 * copy of the License at http://www.apache.org/licenses/LICENSE-2.0.         *
 *                                                                            *
 * Unless required by applicable law or agreed to in writing, software        *
 * distributed under the License is distributed on an "AS IS" BASIS,          *
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.   *
 * See the License for the specific language governing permissions and        *
 * limitations under the License.                                             *
 * -------------------------------------------------------------------------- */

#include "SimTKcommon.h"
#include "simmath/internal/common.h"
#include "simmath/internal/GCVSPLUtil.h"

#include <limits>

namespace SimTK {

template <class T>
class Spline_ : public Function_<T> {
public:
    Spline_(int degree, const Vector& x, const Vector_<T>& y) 
    :   impl(new SplineImpl(degree, x, y)) {}

    Spline_() : impl(nullptr) {}

    Spline_(const Spline_& source) : impl(source.impl) 
    {   if (impl) impl->referenceCount++; }

    Spline_& operator=(const Spline_& source) {
        if (impl) {
            impl->referenceCount--;
            if (impl->referenceCount == 0)
                delete impl;
        }
        impl = source.impl;
        if (impl) impl->referenceCount++;
        return *this;
    }

    ~Spline_() {
        if (impl) {
            impl->referenceCount--;
            if (impl->referenceCount == 0)
                delete impl;
        }
    }

    T calcValue(Real x) const {
        assert(impl);
        return impl->getValue(x);
    }

    T calcDerivative(int order, Real x) const {
        assert(impl);
        assert(order > 0);
        return impl->getDerivative(order, x);
    }

    const Vector& getControlPointLocations() const {
        assert(impl);
        return impl->x;
    }
    const Vector_<T>& getControlPointValues() const {
        assert(impl);
        return impl->y;
    }

    int getSplineDegree() const {
        assert(impl);
        return impl->degree;
    }

    T calcValue(const Vector& x) const override {
        assert(x.size() == 1);
        return calcValue(x[0]);
    }
    T calcDerivative(const Array_<int>& derivComponents, const Vector& x) const
        override
    {   assert(x.size() == 1);
        return calcDerivative((int)derivComponents.size(), x[0]); }
    T calcDerivative(const std::vector<int>& derivComponents, 
                     const Vector& x) const 
    {   assert(x.size() == 1);
        return calcDerivative((int)derivComponents.size(), x[0]); }

    int getArgumentSize() const override {return 1;}
    int getMaxDerivativeOrder() const override 
    {   return std::numeric_limits<int>::max(); }
    Spline_* clone() const override {return new Spline_(*this);}

private:
    class SplineImpl;
    SplineImpl* impl;
};

typedef Spline_<Real> Spline;

template <class T>
class Spline_<T>::SplineImpl {
public:
    SplineImpl(int degree, const Vector& x, const Vector_<T>& y) 
    :   referenceCount(1), degree(degree), x(x), y(y) {}
    ~SplineImpl() {
        assert(referenceCount == 0);
    }
    T getValue(Real t) const {
        return GCVSPLUtil::splder(0, degree, t, x, y);
    }
    T getDerivative(int derivOrder, Real t) const {
        return GCVSPLUtil::splder(derivOrder, degree, t, x, y);
    }
    int         referenceCount;
    int         degree;
    Vector      x;
    Vector_<T>  y;
};

} // namespace SimTK

#endif // SimTK_SIMMATH_SPLINE_H_