feat: precompute king attack tables

1 files changed, 14 insertions, 5 deletions

diff --git a/src/board.c b/src/board.c
index 83fe8ce..a0b1bb7 100644
--- a/src/board.c
+++ b/src/board.c
@@ -18,7 +18,7 @@ void print_bitboard(Bitboard bb) {
 
 void precompute_knight_attack_table(Bitboard attacks[64]) {
   for (int index = 0; index < 64; index++) {
-    U64 position = (U64)1 << index;
+    U64 position = BIT << index;
 
     attacks[index] =
       ((position & notAFile & notBFile) << 6) |
@@ -32,6 +32,17 @@ void precompute_knight_attack_table(Bitboard attacks[64]) {
   }
 }
 
+void precompute_king_attack_table(Bitboard attacks[64]) {
+  for (int index = 0; index < 64; index++) {
+    U64 position = BIT << index;
+
+    attacks[index] =
+      (position & notAFile) << 7  | (position << 8) | (position & notHFile) << 9 |
+      (position & notAFile) >> 1  |                   (position & notHFile) << 1 |
+      (position & notAFile) >> 9  | (position >> 8) | (position & notHFile) >> 7;
+  }
+}
+
 Board parse_FEN(char* FEN) {
   Board board;
   for (int i = 0; i < 12; i++) board.pieces[i] = 0;
@@ -42,7 +53,7 @@ Board parse_FEN(char* FEN) {
   for (int k = 0; k < strlen(FEN); k++) {
     int c = FEN[k];
     int index = rank * 8 + file;
-    Bitboard position = (Bitboard)1 << index;
+    Bitboard position = BIT << index;
 
     if (c > '0' && c <= '8') file += c - '0';
     else {
@@ -87,8 +98,6 @@ Board parse_FEN(char* FEN) {
           rank--;
           file = -1; // So that it becomes 0
           break;
-        case ' ': // TODO: parse everything after
-          return board;
       }
       file++;
     }
@@ -103,7 +112,7 @@ void print_board(Board board) {
     printf("%i|", rank + 1);
     for (int file = 0; file < 8; file++) {
       int index = rank * 8 + file;
-      Bitboard position = (Bitboard)1 << index;
+      Bitboard position = BIT << index;
 
       int found = 0;
       for (int piece = 0; piece < 12; piece++) {