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Chess - Programming - Polyglot Book Format - Piece

Piece is the exclusive or of entries from the RANDOM_PIECE sub-array, one for each piece on the board.

The offset of the entry in RANDOM_PIECE corresponding to a piece is computed as follows:
```
offset_piece=64*Piece_Type+8*Rank+File;
```

Rank and File are counted from 0 to 7:

Square	File	Rank
a1	0	0
h1	7	0
a8	0	7
h8	7	7

“Piece_Type” is encoded as:

  constexpr int BlackPawn   = 0;
  constexpr int WhitePawn   = 1;
  constexpr int BlackKnight = 2;
  constexpr int WhiteKnight = 3;
  constexpr int BlackBishop = 4;
  constexpr int WhiteBishop = 5;
  constexpr int BlackRook   = 6;
  constexpr int WhitekRook  = 7;
  constexpr int BlackQueen  = 8;
  constexpr int WhiteQueen  = 9;
  constexpr int BlackKing   = 10;
  constexpr int WhiteKing   = 11;
  constexpr int None        = 12;

Piece