implemented pseudo-move generation for pawn moves

engine/src/bitboard/attacks.rs

@@ -0,0 +1,29 @@
+use super::board::Board;
+
+impl Board {
+
+  const RANK_2: u64 = 0x0000_0000_0000_FF00;
+  const RANK_7: u64 = 0x00FF_0000_0000_0000;
+
+  pub fn get_pseudo_pawn_moves(&self, sq: u32) -> u64 {
+    let pawn: u64 = 1 << sq;
+    let mut move_mask: u64 = 0u64;
+    let move_offset: i8 = 8 - 16 * self.side_to_move as i8;
+
+    let next_sq: u64 = if move_offset > 0 {pawn << move_offset} else {pawn >> -move_offset};
+    if (self.occupancy[2] & next_sq) == 0 {
+      move_mask |= next_sq;
+
+      if (self.side_to_move == 0 && pawn & Self::RANK_2 != 0)
+        || (self.side_to_move == 1 && pawn & Self::RANK_7 != 0) {
+
+        let next_sq: u64 = if move_offset > 0 {next_sq << move_offset} else {next_sq >> -move_offset};
+        if (self.occupancy[2] & next_sq) == 0 {
+          move_mask |= next_sq;
+        }
+      }
+    }
+
+    return move_mask;
+  }
+}