private function FindMovesToTile($nRank, $nFile)
{
$this->nCalls++;
$Kings;
$Knights;
$Pawns;
$Rooks;
$Bishops;
// Bitmaps for storing attacking pieces.
$n64One = new BitBoard('0x1');
// Find the pieces a king/knight/rook/bishop could attack from this position.
// Queens will show up in the rook and bishop bitmaps.
$Kings = $this->FindTilesAttackedByKing($nRank, $nFile)->_AND(BitBoard::_OR_($this->n64BKing, $this->n64WKing));
$Bishops = $this->FindTilesAttackedByBishop($nRank, $nFile)->_AND(BitBoard::_OR_($this->n64BBishops, $this->n64WBishops)->_OR($this->n64WQueens)->_OR($this->n64BQueens));
$Rooks = $this->FindTilesAttackedByRook($nRank, $nFile)->_AND(BitBoard::_OR_($this->n64BRooks, $this->n64WRooks)->_OR($this->n64WQueens)->_OR($this->n64BQueens));
$Knights = $this->FindTilesAttackedByKnight($nRank, $nFile)->_AND(BitBoard::_OR_($this->n64WKnights, $this->n64BKnights));
$Pawns = new BitBoard();
// Pawns are handled differently. The pawn's move to bitmap is taken and ANDed with the tile
// provided to the function so we know if the pawn can move to that tile. The pawn square is
// usually one more/less than the rank, unless the rank is 3 or 4 in which case the starting
// rank for the pawn may also be checked to see if the pawn can jump two tiles.
if ($nRank > 0 && !$this->WPawnAttacks[($nRank - 1) * 8 + $nFile]->is_zero() && !$this->Tiles[$nRank * 8 + $nFile]->is_zero()) {
if (!BitBoard::_AND_($this->n64WPawns, $this->Tiles[($nRank - 1) * 8 + $nFile])->is_zero()) {
$Pawns = $this->Tiles[($nRank - 1) * 8 + $nFile]->duplicate();
}
}
if ($nRank == 3) {
// Need to check if there is a blocking piece before this pawn can be added.
if (!BitBoard::_AND_($this->n64WPawns, $this->Tiles[($nRank - 2) * 8 + $nFile])->is_zero() && BitBoard::_AND_($this->n64All, $this->Tiles[($nRank - 1) * 8 + $nFile])->is_zero()) {
$Pawns->_OR($this->Tiles[($nRank - 2) * 8 + $nFile]);
}
}
if ($nRank < 7 && !$this->BPawnAttacks[($nRank + 1) * 8 + $nFile]->is_zero() && !$this->Tiles[$nRank * 8 + $nFile]->is_zero()) {
if (!BitBoard::_AND_($this->n64BPawns, $this->Tiles[($nRank + 1) * 8 + $nFile])->is_zero()) {
$Pawns->_OR($this->Tiles[($nRank + 1) * 8 + $nFile]);
}
}
if ($nRank == 4) {
if (!BitBoard::_AND_($this->n64BPawns, $this->Tiles[($nRank + 2) * 8 + $nFile])->is_zero() && BitBoard::_AND_($this->n64All, $this->Tiles[($nRank + 1) * 8 + $nFile])->is_zero()) {
$Pawns->_OR($this->Tiles[($nRank + 2) * 8 + $nFile]);
}
}
//if ($this->PlayerTurn == 0)
//{
// Pawns = FindTilesAttackedByPawn(nRank, nFile) & $this->n64BPawns;
// // If not the bottom two ranks we can check if a pawn can move to this rank.
// if (nRank > 1)
// {
// // See if there is a pawn one rank below. If so add it to the bitmap.
// if (($this->n64WPawns & $this->Tiles[(nRank - 1) * 8 + nFile]) > 0)
// Pawns |= $this->Tiles[(nRank - 1) * 8 + nFile];
// // As there is no pawn one rank below, check if this is rank 3 which means
// // a pawn two ranks below in rank 1 could move up to here as long as there
// // is no piece in the way
// else if (nRank == 3 && ($this->n64WPawns & $this->Tiles[(nRank - 2) * 8 + nFile]) > 0 &&
// ($this->n64All & $this->Tiles[(nRank - 2) * 8 + nFile]) > 0)
// Pawns |= $this->Tiles[(nRank - 2) * 8 + nFile];
// }
// $this->PlayerTurn = 1;
// Pawns |= FindTilesAttackedByPawn(nRank, nFile) & $this->n64WPawns;
// if (nRank < 6)
// {
// if (($this->n64BPawns & $this->Tiles[(nRank + 1) * 8 + nFile]) > 0)
// Pawns |= $this->Tiles[(nRank + 1) * 8 + nFile];
// else if (nRank == 4 && ($this->n64BPawns & $this->Tiles[(nRank + 2) * 8 + nFile]) > 0 &&
// ($this->n64All & $this->Tiles[(nRank + 2) * 8 + nFile]) > 0)
// Pawns |= $this->Tiles[(nRank + 2) * 8 + nFile];
// }
// $this->PlayerTurn = 0;
//}
//else if($this->PlayerTurn == 1)
//{
// Pawns = FindTilesAttackedByPawn(nRank, nFile) & $this->n64WPawns;
// if (nRank < 6)
// {
// if (($this->n64BPawns & $this->Tiles[(nRank + 1) * 8 + nFile]) > 0)
// Pawns |= $this->Tiles[(nRank + 1) * 8 + nFile];
// else if (nRank == 4 && ($this->n64BPawns & $this->Tiles[(nRank + 2) * 8 + nFile]) > 0 &&
// ($this->n64All & $this->Tiles[(nRank + 2) * 8 + nFile]) > 0)
// Pawns |= $this->Tiles[(nRank + 2) * 8 + nFile];
// }
// $this->PlayerTurn = 0;
// Pawns |= FindTilesAttackedByPawn(nRank, nFile) & $this->n64BPawns;
// if (nRank > 1)
// {
// if (($this->n64WPawns & $this->Tiles[(nRank - 1) * 8 + nFile]) > 0)
// Pawns |= $this->Tiles[(nRank - 1) * 8 + nFile];
// else if (nRank == 3 && ($this->n64WPawns & $this->Tiles[(nRank - 2) * 8 + nFile]) > 0 &&
// ($this->n64All & $this->Tiles[(nRank - 2) * 8 + nFile]) > 0)
// Pawns |= $this->Tiles[(nRank - 2) * 8 + nFile];
// }
// $this->PlayerTurn = 1;
//}
// Combine all bitmaps and return.
return $Kings->_OR($Bishops)->_OR($Rooks)->_OR($Knights)->_OR($Pawns);
}