BitFieldCoder.cpp

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#include "DDSegmentation/BitFieldCoder.h"
 
#include <cmath>
#include <algorithm>
#include <stdexcept>
 
namespace dd4hep{
 
  namespace DDSegmentation {
  
    BitFieldElement::BitFieldElement( const std::string& fieldName,
                                      unsigned fieldOffset, int signedWidth ) :
      _mask(0), 
      _offset( fieldOffset ),
      _width( abs( signedWidth ) ),
      _minVal(0),
      _maxVal(0),
      _isSigned( signedWidth < 0 ),
      _name( fieldName ) {
    
      // sanity check
      if( _offset > 63 || _offset+_width > 64 ) {
      
        std::stringstream s ;
        s << " BitFieldElement '" << _name << "': out of range -  offset : " 
          << _offset  << " width " << _width  ;
      
        throw( std::runtime_error( s.str() ) ) ;
      }
    
      _mask = ( ( 0x0001LL << _width ) - 1 ) << _offset ;
    
    
      // compute extreme values for later checks
      if( _isSigned ){
      
        _minVal =  ( 1LL << ( _width - 1 ) ) - ( 1LL << _width )  ;
        _maxVal =  ( 1LL << ( _width - 1 ) ) - 1 ;
      
      } else {
        _maxVal = 0x0001<<_width  ;
      }
    }
  
    FieldID BitFieldElement::value(CellID id) const { 
      if(  _isSigned   ) {
        FieldID val = ( id & _mask ) >> _offset ;
        if( ( val  & ( 1LL << ( _width - 1 ) ) ) != 0 ) { // negative value
          val -= ( 1LL << _width );
        }
        return val ;
      } else { 
        return  ( id & _mask ) >> _offset ;
      }
    }
 
    void BitFieldElement::set(CellID& field, FieldID in) const {
    
      // check range 
      if( in < _minVal || in > _maxVal  ) {
        std::stringstream s ;
        s << " BitFieldElement '" << _name << "': out of range : " << in 
          << " for width " << _width  ; 
        throw( std::runtime_error( s.str() ) );
      }
    
      field &= ~_mask ;  // zero out the field's range
      field |=  ( (  in  << _offset )  & _mask  ) ; 
    }
  
 
 
 
    size_t BitFieldCoder::index( const std::string& name) const {
    
      IndexMap::const_iterator it = _map.find( name ) ;
    
      if( it != _map.end() ) 
      
        return it->second  ;
    
      else
        throw std::runtime_error(" BitFieldElement: unknown name: " + name ) ;
    }
  
    unsigned BitFieldCoder::highestBit() const {
    
      unsigned hb(0) ;
    
      for(unsigned i=0;i<_fields.size();i++){
      
        if( hb < ( _fields[i].offset() + _fields[i].width() ) )
          hb = _fields[i].offset() + _fields[i].width()  ;
      }    
      return hb ;
    }
 
 
    std::string BitFieldCoder::valueString(CellID bitfield) const {
 
      std::stringstream  os ;
 
      for(unsigned i=0;i<_fields.size();i++){
      
        if( i != 0 )   os << "," ;
 
        os << _fields[i].name() <<  ":" << _fields[i].value(bitfield) ;
 
      }
      return os.str() ;
    }
  
    std::string BitFieldCoder::fieldDescription() const {
    
      std::stringstream  os ;
    
      for(unsigned i=0;i<_fields.size();i++){
      
        if( i != 0 )   os << "," ;
      
        os << _fields[i].name() <<  ":"
           << _fields[i].offset() << ":" ;
      
        if(  _fields[i].isSigned()  )
          os << "-" ;
      
        os  << _fields[i].width() ;
      
      }
 
      return os.str() ;
    }
 
    void BitFieldCoder::addField( const std::string& name,  unsigned offset, int width ){
 
      
      _fields.emplace_back(name, offset, width);
      BitFieldElement& bfv = _fields.back() ;
 
      _map[ name ] = _fields.size()-1 ;
 
      if( _joined & bfv.mask()  ) {
      
        std::stringstream s ;
        s << " BitFieldElement::addField(" << name << "): bits already used " << std::hex << _joined
          << " for mask " <<  bfv.mask() ;
 
        throw( std::runtime_error( s.str() ) ) ;
      
      }
 
      _joined |= bfv.mask() ;
 
    }
 
    void BitFieldCoder::init( const std::string& initString) {
 
      unsigned offset = 0  ;
    
      // need to compute bit field masks and offsets ...
      std::vector<std::string> fieldDescriptors ;
      StringTokenizer t( fieldDescriptors ,',') ;
 
      std::for_each( initString.begin(), initString.end(), t ) ; 
 
      for(unsigned i=0; i< fieldDescriptors.size() ; i++ ){
      
        std::vector<std::string> subfields ;
        StringTokenizer ts( subfields ,':') ;
      
        std::for_each( fieldDescriptors[i].begin(), fieldDescriptors[i].end(), ts );
 
        std::string name ; 
        int  width ; 
        unsigned thisOffset ;
 
        switch( subfields.size() ){
    
        case 2: 
 
          name = subfields[0] ; 
          width = atol( subfields[1].c_str()  ) ;
          thisOffset = offset ;
 
          offset += abs( width ) ;
    
          break ;
    
        case 3: 
          name = subfields[0] ;
          thisOffset = atol( subfields[1].c_str()  ) ;
          width = atol( subfields[2].c_str()  ) ;
 
          offset = thisOffset + abs( width ) ;
 
          break ;
    
        default:
 
          std::stringstream s ;
          s << " BitFieldCoder: invalid number of subfields " 
            <<  fieldDescriptors[i] ;
 
          throw( std::runtime_error( s.str() ) ) ;
        }
 
        addField( name , thisOffset, width ) ;
      }
    }
 
 
 
 
  } // namespace
 
} // namespace