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#ifndef _MORKCELL_
#define _MORKCELL_ 1

#ifndef _MORK_
#include "mork.h"
#endif

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#define morkDelta_kShift 8 /* 8 bit shift */
#define morkDelta_kChangeMask 0x0FF /* low 8 bit mask */
#define morkDelta_kColumnMask (~ (mork_column) morkDelta_kChangeMask)
#define morkDelta_Init(self,cl,ch) ((self) = ((cl)<<morkDelta_kShift) | (ch))
#define morkDelta_Change(self) ((mork_change) ((self) & morkDelta_kChangeMask))
#define morkDelta_Column(self) ((self) >> morkDelta_kShift)

class morkCell { // minimal cell format

public:
  mork_delta   mCell_Delta;   // encoding of both column and change
  morkAtom*    mCell_Atom;    // content in this cell
  
public:
  morkCell() : mCell_Delta( 0 ), mCell_Atom( 0 ) { }

  morkCell(const morkCell& c)
  : mCell_Delta( c.mCell_Delta ), mCell_Atom( c.mCell_Atom ) { }
  
  // note if ioAtom is non-nil, caller needs to call ioAtom->AddCellUse():
  morkCell(mork_column inCol, mork_change inChange, morkAtom* ioAtom)
  {
    morkDelta_Init(mCell_Delta, inCol,inChange);
    mCell_Atom = ioAtom;
  }

  // note if ioAtom is non-nil, caller needs to call ioAtom->AddCellUse():
  void Init(mork_column inCol, mork_change inChange, morkAtom* ioAtom)
  {
    morkDelta_Init(mCell_Delta,inCol,inChange);
    mCell_Atom = ioAtom;
  }
  
  mork_column  GetColumn() const { return morkDelta_Column(mCell_Delta); }
  mork_change  GetChange() const { return morkDelta_Change(mCell_Delta); }
  
  mork_bool IsCellClean() const { return GetChange() == morkChange_kNil; }
  mork_bool IsCellDirty() const { return GetChange() != morkChange_kNil; }

  void SetCellClean(); // set change to kNil
  void SetCellDirty(); // set change to kAdd
  
  void SetCellColumnDirty(mork_column inCol)
  { this->SetColumnAndChange(inCol, morkChange_kAdd); }
  
  void SetCellColumnClean(mork_column inCol)
  { this->SetColumnAndChange(inCol, morkChange_kNil); }
  
  void         SetColumnAndChange(mork_column inCol, mork_change inChange)
  { morkDelta_Init(mCell_Delta, inCol, inChange); }
    
  morkAtom*  GetAtom() { return mCell_Atom; }
  
  void       SetAtom(morkEnv* ev, morkAtom* ioAtom, morkPool* ioPool);
  // SetAtom() "acquires" the new ioAtom if non-nil, by calling AddCellUse()
  // to increase the refcount, and puts ioAtom into mCell_Atom.  If the old
  // atom in mCell_Atom is non-nil, then it is "released" first by a call to
  // CutCellUse(), and if the use count then becomes zero, then the old atom
  // is deallocated by returning it to the pool ioPool.  (And this is
  // why ioPool is a parameter to this method.)  Note that ioAtom can be nil
  // to cause the cell to refer to nothing, and the old atom in mCell_Atom
  // can also be nil, and all the atom refcounting is handled correctly.
  //
  // Note that if ioAtom was just created, it typically has a zero use count
  // before calling SetAtom().  But use count is one higher after SetAtom().
  
  void       SetYarn(morkEnv* ev, const mdbYarn* inYarn, morkStore* ioStore);
  
  void       AliasYarn(morkEnv* ev, mdbYarn* outYarn) const;
  void       GetYarn(morkEnv* ev, mdbYarn* outYarn) const;
};

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#endif /* _MORKCELL_ */