feat: compute knight attack table

1 files changed, 27 insertions, 5 deletions

diff --git a/src/board.c b/src/board.c
index bc5855f..59b6043 100644
--- a/src/board.c
+++ b/src/board.c
@@ -1,10 +1,32 @@
+#include <stdio.h>
 #include "board.h"
 
-BYTE notation_to_index(char file, int rank) {
-  return (rank - 1) * 8 + (file - 'a');
+int pop_count(Bitboard bb){
+  if (bb == 0) return 0;
+  return pop_count(bb >> 1) + (bb & 1);
 }
 
-void index_to_notation(BYTE index, char notation[2]) {
-  notation[0] = (index & 0b0111) + 'a';
-  notation[1] = (index >> 3) + '1';
+void print_bitboard(Bitboard bb) {
+  for (U64 index = 0; index < 64; index++) {
+    printf("%lu", (bb >> index) & 1);
+    if ((index + 1) % 8 == 0) printf("\n");
+  }
+  printf("\n\n");
+}
+
+
+void precompute_knight_attack_table(Bitboard attacks[64]) {
+  for (int index = 0; index < 64; index++) {
+    U64 position = (U64)1 << index;
+
+    attacks[index] =
+      ((position & notAFile & notBFile) << 6) |
+      ((position & notGFile & notHFile) << 10) |
+      ((position & notAFile) << 15) |
+      ((position & notHFile) << 17) |
+      ((position & notGFile & notHFile) >> 6) |
+      ((position & notAFile & notBFile) >> 10) |
+      ((position & notHFile) >> 15) |
+      ((position & notAFile) >> 17);
+  }
 }