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/Definitions/Algebra.hpp"
#include "Acts/MagneticField/MagneticFieldContext.hpp"
#include "Acts/MagneticField/MagneticFieldProvider.hpp"

namespace Acts {

class NullBField final : public MagneticFieldProvider {
 public:
  struct Cache {
    Cache(const MagneticFieldContext& /*mcfg*/) {}
  };

  NullBField() = default;

  Result<Vector3> getField(const Vector3& position,
                           MagneticFieldProvider::Cache& cache) const override {
    (void)position;
    (void)cache;
    return Result<Vector3>::success(m_BField);
  }

  Result<Vector3> getFieldGradient(
      const Vector3& position, ActsMatrix<3, 3>& derivative,
      MagneticFieldProvider::Cache& cache) const override {
    (void)position;
    (void)derivative;
    (void)cache;
    return Result<Vector3>::success(m_BField);
  }

  Acts::MagneticFieldProvider::Cache makeCache(
      const Acts::MagneticFieldContext& mctx) const override {
    return Acts::MagneticFieldProvider::Cache::make<Cache>(mctx);
  }

  bool isInside(const Vector3& position) const {
    (void)position;
    return true;
  }

 private:
  const Vector3 m_BField = Vector3::Zero();
};
}  // namespace Acts