add custom chess engine

native/chess_engine/src/zobrist.cpp

@@ -0,0 +1,39 @@
+#include "zobrist.h"
+
+namespace chess {
+namespace Zobrist {
+
+uint64_t psq[PIECE_NB][SQUARE_NB];
+uint64_t enpassant[FILE_NB];
+uint64_t castling[16];
+uint64_t side;
+
+namespace {
+struct PRNG {
+    uint64_t s;
+    explicit PRNG(uint64_t seed) : s(seed) {}
+    uint64_t next() {
+        s ^= s >> 12; s ^= s << 25; s ^= s >> 27;
+        return s * 2685821657736338717ULL;
+    }
+};
+}
+
+void init() {
+    PRNG rng(0xC0FFEE123456789Aull);
+
+    for (int p = 0; p < PIECE_NB; ++p)
+        for (int s = 0; s < SQUARE_NB; ++s)
+            psq[p][s] = rng.next();
+
+    for (int f = 0; f < FILE_NB; ++f)
+        enpassant[f] = rng.next();
+
+    for (int c = 0; c < 16; ++c)
+        castling[c] = rng.next();
+
+    side = rng.next();
+}
+
+} // namespace Zobrist
+} // namespace chess