NullBField.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2016-2018 CERN for the benefit of the Acts project
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#pragma once
#include "Acts/MagneticField/MagneticFieldContext.hpp"
#include "Acts/Utilities/Definitions.hpp"

namespace Acts {

class NullBField final {
 public:
  struct Cache {
    Cache(std::reference_wrapper<const MagneticFieldContext> /*mcfg*/) {}
  };

  NullBField() = default;

  Vector3D getField(const Vector3D& /*position*/) const { return m_BField; }

  Vector3D getField(const Vector3D& /*position*/, Cache& /*cache*/) const {
    return m_BField;
  }

  Vector3D getFieldGradient(const Vector3D& /*position*/,
                            ActsMatrixD<3, 3>& /*derivative*/) const {
    return m_BField;
  }

  Vector3D getFieldGradient(const Vector3D& /*position*/,
                            ActsMatrixD<3, 3>& /*derivative*/,
                            Cache& /*cache*/) const {
    return m_BField;
  }

  bool isInside(const Vector3D& /*position*/) const { return true; }

 private:
  const Vector3D m_BField = Vector3D::Zero();
};
}  // namespace Acts