G4SurfBits.hh

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//
// G4SurfBits
//
// Class description:
//
// This class provides a simple container of bits, to be used for
// optimization of tessellated surfaces (G4TessellatedSolid).
// Each bit can be set and tested via the functions SetBitNumber and
// TestBitNumber.
// The default value of all bits is false.
// The size of the container is automatically extended when a bit
// number is either set or tested.  To reduce the memory size of the
// container use the Compact function, this will discard the memory
// occupied by the upper bits that are 0.

// 19.10.12 - Marek Gayer, created and adapted from original implementation
//                         of Root's TBits class by P.Canal
// --------------------------------------------------------------------
#ifndef G4SURFBITS_HH
#define G4SURFBITS_HH

#include <cstring>

#include "G4Types.hh"

class G4SurfBits
{
  public:

    G4SurfBits(unsigned int nbits = 0);
    G4SurfBits(const G4SurfBits&);
    G4SurfBits& operator=(const G4SurfBits&);
   ~G4SurfBits();

    //----- Bit manipulation
    void ResetAllBits(G4bool value = false);  // if value=1 set all bits to 1
    void ResetBitNumber(unsigned int bitnumber);
    void SetBitNumber(unsigned int bitnumber, G4bool value = true);
    G4bool TestBitNumber(unsigned int bitnumber) const;

    //----- Accessors and operator
    G4bool operator[](unsigned int bitnumber) const;

    //----- Optimized setters
    // Each of these will replace the contents of the receiver with the
    // bitvector in the parameter array. The number of bits is changed
    // to nbits. If nbits is smaller than fNBits, the receiver will NOT
    // be compacted.
    void set(unsigned int nbits, const char* array);
    void set(unsigned int nbits, const G4int* array);

    //----- Optimized getters
    // Each of these will replace the contents of the parameter array with the
    // bits in the receiver.  The parameter array must be large enough to hold
    // all of the bits in the receiver.
    // Note on semantics: any bits in the parameter array that go beyond the
    // number of the bits in the receiver will have an unspecified value. For
    // example, if you call Get(Int*) with an array of one integer and the
    // G4SurfBits object has less than 32 bits, then the remaining bits in the
    // integer will have an unspecified value.
    void Get(char* array) const;
    void Get(G4int* array) const;

    //----- Utilities
    void Clear();
    void Compact();               // Reduce the space used.

    unsigned int GetNbits()      const { return fNBits; }
    unsigned int GetNbytes()     const { return fNBytes; }

    void Print() const;  // to show the list of active bits
    void Output(std::ostream &) const;

  protected:

    void ReserveBytes(unsigned int nbytes);

  public:

    unsigned char* fAllBits = nullptr; // [fNBytes] array of UChars

  protected:

    unsigned int fNBits;         // Highest bit set + 1
    unsigned int fNBytes;        // Number of UChars in fAllBits
};

// inline functions...

inline void G4SurfBits::SetBitNumber(unsigned int bitnumber, G4bool value)
{
  // set bit number 'bitnumber' to be value

  if (bitnumber >= fNBits)
  {
    unsigned int new_size = (bitnumber/8) + 1;
    if (new_size > fNBytes)
    {
      if (new_size < 100 * 1024 * 1024) new_size *= 2;
      unsigned char *old_location = fAllBits;
      fAllBits = new unsigned char[new_size];
      std::memcpy(fAllBits,old_location,fNBytes);
      std::memset(fAllBits+fNBytes ,0, new_size-fNBytes);
      fNBytes = new_size;
      delete [] old_location;
    }
    fNBits = bitnumber+1;
  }
  unsigned int loc = bitnumber/8;
  unsigned char bit = bitnumber%8;
  if (value)
    fAllBits[loc] |= (1<<bit);
  else
    fAllBits[loc] &= (0xFF ^ (1<<bit));
}

inline G4bool G4SurfBits::TestBitNumber(unsigned int bitnumber) const
{
  // Return the current value of the bit

  if (bitnumber >= fNBits) return false;
  unsigned int loc = bitnumber/8;
  unsigned char value = fAllBits[loc];
  unsigned char bit = bitnumber%8;
  G4bool result = (value & (1<<bit)) != 0;
  return result;
  // short: return 0 != (fAllBits[bitnumber/8] & (1<< (bitnumber%8)));
}

inline void G4SurfBits::ResetBitNumber(unsigned int bitnumber)
{
  SetBitNumber(bitnumber,false);
}

inline G4bool G4SurfBits::operator[](unsigned int bitnumber) const
{
  return TestBitNumber(bitnumber);
}

#endif