TwoBitFour.h

//-*-C++-*-
/***************************************************************************
 *
 *   Copyright (C) 2008 by Willem van Straten
 *   Licensed under the Academic Free License version 2.1
 *
 ***************************************************************************/
 
// dspsr/Kernel/Classes/dsp/TwoBitFour.h
 
#ifndef __TwoBitFour_h
#define __TwoBitFour_h
 
#include "dsp/TwoBitLookup.h"
 
namespace dsp
{
  class TwoBitFour : public TwoBitLookup
  {
 
  public:
 
    static const unsigned samples_per_byte;
    static const unsigned lookup_block_size;
 
    bool bad;
 
    void lookup_build (TwoBitTable*, JenetAnderson98* = 0);
 
    void nlow_build (TwoBitTable* table);
 
    void get_lookup_block (float* lookup, TwoBitTable* table);
 
    unsigned get_lookup_block_size ();
 
    template<class Iterator>
    inline void prepare (Iterator input, unsigned ndat)
    {
      const unsigned nbyte = ndat / samples_per_byte;
      unsigned total = 0;
 
      nlow = 0;
 
      for (unsigned bt=0; bt < nbyte; bt++)
      {
        nlow += nlow_lookup[ *input ];
        total += *input;
        ++ input;
      }
 
      bad = (total == 0);
    }
    
    template<class Iterator>
    inline void unpack (Iterator& input, unsigned ndat, 
                        float* output, unsigned output_incr, unsigned& _nlow)
    {
      const unsigned nbyte = ndat / samples_per_byte;
      _nlow = nlow;
 
      // if data are complex, divide n_low by two
      nlow /= ndim;
 
      if (nlow < nlow_min)
        nlow = nlow_min;
 
      else if (nlow > nlow_max)
        nlow = nlow_max;
      
      float* lookup = lookup_base + (nlow-nlow_min) * lookup_block_size;
 
      for (unsigned bt=0; bt < nbyte; bt++)
      {
        float* fourval = lookup + *input * samples_per_byte;
        ++ input;
        
        for (unsigned pt=0; pt < samples_per_byte; pt++)
        {
          *output = fourval[pt];
          output += output_incr;
        }
      }
    }
    
  protected:
    
    char nlow_lookup [256];
  };
 
}
 
#endif