[board] Implement BitAnd and BitOr on BitBoard and make it's u64 private

board/src/bitboard.rs

@@ -2,11 +2,20 @@
 
 use crate::square::Square;
 use std::arch::asm;
+use std::ops::{BitAnd, BitOr};
 
 #[derive(Clone, Copy, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd)]
-pub struct BitBoard(pub u64);
+pub struct BitBoard(u64);
 
 impl BitBoard {
+    pub fn empty() -> BitBoard {
+        BitBoard(0)
+    }
+
+    pub fn from_bit_field(bits: u64) -> BitBoard {
+        BitBoard(bits)
+    }
+
     fn is_empty(&self) -> bool {
         self.0 == 0
     }
@@ -38,6 +47,38 @@ impl BitBoard {
     }
 }
 
+impl BitAnd for BitBoard {
+    type Output = BitBoard;
+
+    fn bitand(self, rhs: Self) -> Self {
+        BitBoard(self.0 & rhs.0)
+    }
+}
+
+impl BitAnd<&BitBoard> for BitBoard {
+    type Output = BitBoard;
+
+    fn bitand(self, rhs: &Self) -> Self {
+        BitBoard(self.0 & rhs.0)
+    }
+}
+
+impl BitOr for BitBoard {
+    type Output = BitBoard;
+
+    fn bitor(self, rhs: Self) -> Self {
+        BitBoard(self.0 | rhs.0)
+    }
+}
+
+impl BitOr<&BitBoard> for BitBoard {
+    type Output = BitBoard;
+
+    fn bitor(self, rhs: &Self) -> Self {
+        BitBoard(self.0 | rhs.0)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;