return join('/', @rows);
}
+# Returns a compact bit string describing the same data as fen().
+# This is encoded using a Huffman-like encoding, and should be
+# typically about 1/3 the number of bytes.
+sub bitpacked_fen {
+ my ($board) = @_;
+ my $bits = "";
+
+ for my $row (0..7) {
+ for my $col (0..7) {
+ my $piece = $board->[$row][$col];
+ if ($piece eq '-') {
+ $bits .= "0";
+ next;
+ }
+
+ my $color = (lc($piece) eq $piece) ? 0 : 1;
+ $bits .= "1" . $color;
+
+ if (lc($piece) eq 'p') {
+ $bits .= "0";
+ } elsif (lc($piece) eq 'n') {
+ $bits .= "100";
+ } elsif (lc($piece) eq 'b') {
+ $bits .= "101";
+ } elsif (lc($piece) eq 'r') {
+ $bits .= "1110";
+ } elsif (lc($piece) eq 'q') {
+ $bits .= "11110";
+ } elsif (lc($piece) eq 'k') {
+ $bits .= "11111";
+ } else {
+ die "Unknown piece $piece";
+ }
+ }
+ }
+
+ return pack('b*', $bits);
+}
+
sub can_reach {
my ($board, $piece, $from_row, $from_col, $to_row, $to_col) = @_;
return $fen;
}
+# Returns a compact bit string describing the same data as fen(),
+# except for the half-move and full-move clock.
+sub bitpacked_fen {
+ my $pos = shift;
+ my $board = $pos->{'board'}->bitpacked_fen();
+
+ my $bits = "";
+ if ($pos->{'toplay'} eq 'W') {
+ $bits .= "0";
+ } else {
+ $bits .= "1";
+ }
+
+ $bits .= $pos->{'white_castle_k'};
+ $bits .= $pos->{'white_castle_q'};
+ $bits .= $pos->{'black_castle_k'};
+ $bits .= $pos->{'black_castle_q'};
+
+ my $col = $pos->{'ep_file_num'};
+ if ($col == -1) {
+ $bits .= "0";
+ } else {
+ $bits .= "1";
+ $bits .= (qw(000 001 010 011 100 101 110 111))[$col];
+ }
+
+ return $board . pack('b*', $bits);
+}
+
sub to_json_hash {
my $pos = shift;
my $json = { %$pos, fen => $pos->fen() };