Torque2D/engine/source/collection/bitTables.h

//-----------------------------------------------------------------------------
// Copyright (c) 2013 GarageGames, LLC
//
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//-----------------------------------------------------------------------------

#ifndef _BITTABLES_H_
#define _BITTABLES_H_

#ifndef _PLATFORM_H_
#include "platform/platform.h"
#endif

class BitTables
{
  private:
   static bool mTablesBuilt;        ///< For first time build
   static S8   mHighBit[256];       ///< I.e. crude logarithm
   static S8   mWhichOn[256][8];    ///< Unroll a bitset collection (note
   static S8   mNumOn[256];         //    ptr table wastes same amt.)

  public:
   BitTables();

   /// How many bits are on?
   static const S32   numOn(U8 b)       {  return mNumOn[b];      }

   /// Return a pointer to 8 S8's, which are set according to which bits are set in the passed value.
   static const S8 *  whichOn(U8 b)     {  return mWhichOn[b];    }

   static const S32   highBit(U8 b)     {  return mHighBit[b];    }


   static S32 getPower16(U16 x)   { return x<256 ? mHighBit[x] : mHighBit[x>>8]+8; }
   static S32 getPower32(U32 x){
                  if( x < (1<<16) )
                     return( x < (1<<8)  ? mHighBit[x] : mHighBit[x>>8]+8 );
                  else
                     return( x < (1<<24) ? mHighBit[x>>16]+16 : mHighBit[x>>24]+24 );
                 }
};

#endif