EvtStreamAdapter.hh

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/*******************************************************************************
 * Project: BaBar detector at the SLAC PEP-II B-factory
 * Package: EvtGenBase
 *    File: $Id: EvtStreamAdapter.hh,v 1.1.1.2 2007/10/26 05:03:14 pingrg Exp $
 *  Author: Alexei Dvoretskii, dvoretsk@slac.stanford.edu, 2001-2002
 *
 * Copyright (C) 2002 Caltech
 *******************************************************************************/
 
// Stream adapters are used to convert a stream-like input (for example,
// a file containing N entries) to an STL like iterator interface. There
// must be a way to get point from the stream, and also an indicator of the
// end of the stream.
 
#ifndef EVT_STREAM_ADAPTER_HH
#define EVT_STREAM_ADAPTER_HH
 
template <class Point> class EvtStreamAdapter {
public:
  EvtStreamAdapter() {}
  virtual ~EvtStreamAdapter() {}
  virtual EvtStreamAdapter* clone() const  = 0;
  virtual Point             currentValue() = 0;
  virtual void              advance()      = 0;
  virtual bool              pastEnd()      = 0;
};
 
// N points are read from a generated stream.
 
template <class Point, class Generator>
class EvtGenStreamAdapter : public EvtStreamAdapter<Point> {
public:
  EvtGenStreamAdapter( Generator gen, int count ) : _gen( gen ), _count( count ) {}
 
  virtual ~EvtGenStreamAdapter() {}
 
  virtual EvtStreamAdapter<Point>* clone() const { return new EvtGenStreamAdapter( *this ); }
  virtual Point                    currentValue() { return _gen(); }
  virtual bool                     pastEnd() { return ( _count <= 0 ); }
  virtual void                     advance() { _count--; }
 
private:
  Generator _gen;
  int       _count; // also serves as past the end indicator
};
 
// Only points satisfying a predicate are read from the stream.
 
template <class Point, class Iterator, class Predicate>
class EvtPredStreamAdapter : public EvtStreamAdapter<Point> {
public:
  EvtPredStreamAdapter( Predicate pred, Iterator it, Iterator end )
      : _pred( pred ), _it( it ), _end( end ) {}
  virtual ~EvtPredStreamAdapter() {}
 
  virtual EvtStreamAdapter<Point>* clone() const { return new EvtPredStreamAdapter( *this ); }
  virtual Point                    currentValue() {
    Point value;
    while ( !pastEnd() )
    {
 
      value = *_it;
      if ( _pred( value ) ) break;
      _it++;
    }
    return value;
  }
 
  virtual bool pastEnd() { return _it == _end; }
  virtual void advance() { _it++; }
 
private:
  Predicate _pred;
  Iterator  _it;
  Iterator  _end;
};
 
#endif