MTF by Eugene Shelwien

mtf_shelwien.cpp

template< int Mode=0 >
struct MTF {

  enum{ CNUM=256 };
  typedef short ranktypeF;
  typedef byte  ranktypeB;

  ranktypeF RankF[CNUM]; 
  ranktypeB RankB[CNUM]; 

  void Init( void ) {
    uint i;
    for( i=0; i<CNUM; i++ ) RankF[i] = i;
    for( i=0; i<CNUM; i++ ) RankB[i] = i;
  }

  byte Transform( byte c ) {
    return Mode ? Inverse(c) : Forward(c);
  }

  byte Forward( byte c ) {
    uint j; 
//printf( "<%02X ", c );
    ranktypeF d = RankF[c];
//printf( ">%02X\n", d );
//getc(stdin);
    for( j=0; j<CNUM; j++ ) RankF[j] += ( RankF[j]<d );
    RankF[c] = 0;
    return d;
  }

  byte Inverse( byte c ) {
    uint j;
    uint d = RankB[c];
    for( j=c; j>0; j-- ) RankB[j]=RankB[j-1];
    RankB[0] = d;
    return d;
  }

};