cxx: expose c++ code

Cargo.lock

@@ -251,6 +251,7 @@ name = "tictactoe-rust-foropenspiel"
 version = "0.1.0"
 dependencies = [
  "cxx",
+ "cxx-build",
 ]
 
 [[package]]

Cargo.toml

@@ -5,3 +5,6 @@ edition = "2024"
 
 [dependencies]
 cxx = "1.0.192"
+
+[build-dependencies]
+cxx-build = "1.0.192"

build.rs

@@ -0,0 +1,9 @@
+fn main() {
+    cxx_build::bridge("src/game.rs")
+        .file("src/main.cc")
+        .compile("tictactoe-rust-foropenspiel");
+
+    println!("cargo:rerun-if-changed=src/game.rs");
+    println!("cargo:rerun-if-changed=src/game.cc");
+    println!("cargo:rerun-if-changed=include/game.h");
+}

include/main.h

@@ -0,0 +1,3 @@
+#pragma once
+
+void run_cpp_demo();

src/game.rs

@@ -1,7 +1,7 @@
 use std::{fmt, str};
 
 #[cxx::bridge]
-mod ffi {
+pub mod ffi {
     // Rust types and signatures exposed to C++.
     extern "Rust" {
         type Player;
@@ -15,6 +15,8 @@ mod ffi {
 
     // C++ types and signatures exposed to Rust.
     unsafe extern "C++" {
+        include!("tictactoe-rust-foropenspiel/include/main.h");
+        fn run_cpp_demo();
     }
 }
 

src/main.cc

@@ -0,0 +1,21 @@
+#include "tictactoe-rust-foropenspiel/include/main.h"
+#include "tictactoe-rust-foropenspiel/src/game.rs.h"
+#include <iomanip>
+#include <iostream>
+#include <random>
+#include <vector>
+
+void run_cpp_demo() {
+  rust::Box<GameState> game = init();
+
+  std::random_device rd;
+  std::mt19937 gen(rd());
+
+  rust::Vec<size_t> actions = game->legal_actions();
+  while (!actions.empty()) {
+    std::uniform_int_distribution<size_t> dis(0, actions.size() - 1);
+    game->do_action(actions[dis(gen)]);
+    actions = game->legal_actions();
+  }
+  std::cout << "Result: \n" << game->to_string().c_str();
+}

src/main.rs

@@ -1,13 +1,7 @@
 mod game;
 
-use game::GameState;
-
 fn main() {
-    let mut game = GameState::default();
-    let mut actions = game.legal_actions();
-    while !actions.is_empty() {
-        game.do_action(actions[0]);
-        actions = game.legal_actions();
-    }
-    println!("Result: \n{game}");
-}
+    println!("--- Calling C++ from Rust ---");
+    game::ffi::run_cpp_demo();
+    println!("--- Back in Rust ---");
+}