implemented general move generation methdod for kings

engine/src/bitboard/movegen/kings.rs

@@ -1 +1,35 @@
-use super::*;
+use super::*;
+
+impl Board {
+
+  fn add_king_moves(&self, capture_buffer: &mut MoveBuffer, quiet_buffer: &mut MoveBuffer, move_mask: u64) {
+    let piece_index = 5 + self.side_to_move * 6;
+    let mut kings = self.bitboards[piece_index as usize];
+    let empty = !self.occupancy[2];
+    let opponents = self.occupancy[1 - self.side_to_move as usize];
+    while kings != 0 {
+      let from_sq = pop_lsb(&mut kings);
+      let move_map = self.get_pseudo_king_moves(from_sq) & move_mask;
+
+      let mut quiet_map = move_map & empty;
+      let mut capture_map = move_map & opponents;
+
+      while quiet_map != 0 {
+        let to_sq = pop_lsb(&mut quiet_map);
+        quiet_buffer.add(BitMove::quiet(
+          from_sq as u8,
+          to_sq as u8,
+          None
+        ));
+      }
+      while capture_map != 0 {
+        let to_sq = pop_lsb(&mut capture_map);
+        capture_buffer.add(BitMove::capture(
+          from_sq as u8,
+          to_sq as u8,
+          None
+        ));
+      }
+    }
+  }
+}