BlockingPrescaler_module.cc

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// BlockingPrescaler.
//
// Accept m in n events with offset. So, for blockSize (m) = 5,
// stepSize (n) = 7 and offset = 4, the filter will accept events 5-9
// inclusive, 12-16 inclusive, 19-23 inclusive, etc.
//
// Note that BlockingPrescaler prescales based on the number of events
// seen by this module, *not* the event number as recorded by EventID.
//

#include "art/Framework/Core/EDFilter.h"
#include "art/Framework/Core/Frameworkfwd.h"
#include "art/Framework/Core/ModuleMacros.h"
#include "fhiclcpp/types/Atom.h"

using namespace fhicl;

namespace art {
  class BlockingPrescaler;
}

// ======================================================================

class art::BlockingPrescaler : public EDFilter {
public:
  struct Config {
    Atom<size_t> blockSize{Name("blockSize"), 1};
    Atom<size_t> stepSize{Name("stepSize")};
    Atom<size_t> offset{Name("offset"), 0};
  };

  using Parameters = EDFilter::Table<Config>;
  explicit BlockingPrescaler(Parameters const&);

  virtual bool filter(Event&) override;

private:
  size_t count_{};
  size_t const m_; // accept m in n (sequentially).
  size_t const n_;
  size_t const offset_; // First accepted event is 1 + offset.

}; // BlockingPrescaler

// ======================================================================

art::BlockingPrescaler::BlockingPrescaler(Parameters const& config)
  : m_{config().blockSize()}
  , n_{config().stepSize()}
  , offset_{config().offset()}
{}

bool
art::BlockingPrescaler::filter(Event&)
{
  bool const result{(count_ >= offset_) && ((count_ - offset_) % n_) < m_};
  ++count_;
  return result;
}

DEFINE_ART_MODULE(art::BlockingPrescaler)