Add board/position output to a bitpacked format.

[remoteglot] / Board.pm

diff --git a/Board.pm b/Board.pm
index 39c8134096b5897a0e7bd0ff47baad0441fe310f..d2a6e0e425f7b48c8584c47e07e1692fd42ab604 100644 (file)
--- a/Board.pm
+++ b/Board.pm
@@ -221,6 +221,45 @@ sub fen {
        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) = @_;