works

Cargo.lock

@@ -203,6 +203,14 @@ dependencies = [
  "rand",
 ]
 
+[[package]]
+name = "minmax_wrapper"
+version = "0.1.0"
+dependencies = [
+ "jni",
+ "minmax",
+]
+
 [[package]]
 name = "once_cell"
 version = "1.17.0"
@@ -293,14 +301,6 @@ dependencies = [
  "getrandom",
 ]
 
-[[package]]
-name = "rs-wrapper"
-version = "0.1.0"
-dependencies = [
- "jni",
- "minmax",
-]
-
 [[package]]
 name = "rustix"
 version = "0.36.6"

build_and_run.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+
+if ! which rustc > /dev/null;
+then
+    echo "ERROR: Rust must be installed: https://www.rust-lang.org/tools/install"
+    exit 1
+fi
+
+echo "${BASH_SOURCE[0]}"
+
+SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
+
+echo "Building Rust library..."
+cargo build --release "--manifest-path=$SCRIPT_DIR/Cargo.toml"
+
+export LD_LIBRARY_PATH="$SCRIPT_DIR/target/release"
+echo "Setting LD_LIBRARY_PATH to $LD_LIBRARY_PATH"
+
+echo "Running Java tests. If this fails, there's something wrong :/"
+cd "$SCRIPT_DIR/minmax-java"
+./gradlew build

minmax-java/src/main/java/ch/bbw/m411/connect4/Connect4ArenaMain.java

@@ -67,65 +67,7 @@ public class Connect4ArenaMain {
     }
 
     boolean isWinning(Stone[] board, Stone forColor) {
-        var increment = 0;
-        for (int i = 27; i >= 0; i--) {
-            if (forColor != board[i]) {
-                increment = 0;
-                continue;
-            }
-
-            // Horizontal reset
-            if (i == 20 || i == 13 || i == 6) {
-                increment = 0;
-            }
-
-            increment++;
-            // Horizontal
-            if (increment == 4) {
-                return true;
-            }
-
-            if (i > 20) {
-                // Vertical
-                var vertical = true;
-                for (int y = i - 7; y >= 0; y -= 7) {
-                    if (board[y] != forColor) {
-                        vertical = false;
-                        break;
-                    }
-                }
-                if (vertical) {
-                    return true;
-                }
-                // Diagonally
-                if (i <= 24) {
-                    var diagonal = true;
-                    for (int y = i; y >= 0; y -= 7 - 1) {
-                        if (board[y] != forColor) {
-                            diagonal = false;
-                            break;
-                        }
-                    }
-                    if (diagonal) {
-                        return true;
-                    }
-                }
-
-                if (i >= 24) {
-                    var diagonal = true;
-                    for (int y = i; y >= 0; y -= 7 + 1) {
-                        if (board[y] != forColor) {
-                            diagonal = false;
-                            break;
-                        }
-                    }
-                    if (diagonal) {
-                        return true;
-                    }
-                }
-            }
-        }
-        return false;
+        return RustPlayer.isWinning(board, forColor);
     }
 
     public enum Stone {

minmax-java/src/main/java/ch/bbw/m411/connect4/RustPlayer.java

@@ -2,12 +2,13 @@ package ch.bbw.m411.connect4;
 
 public class RustPlayer extends Connect4ArenaMain.DefaultPlayer {
     private static native int rustPlay(byte player, byte[] board);
+    private static native int rustBoardWinner(byte[] board);
 
     static {
         // This actually loads the shared object that we'll be creating.
         // The actual location of the .so or .dll may differ based on your
         // platform.
-        System.loadLibrary("rs_wrapper");
+        System.loadLibrary("minmax_wrapper");
     }
 
     static byte[] encodeBoard(Connect4ArenaMain.Stone[] board) {
@@ -27,6 +28,16 @@ public class RustPlayer extends Connect4ArenaMain.DefaultPlayer {
         return boardBuf;
     }
 
+    public static boolean isWinning(Connect4ArenaMain.Stone[] board, Connect4ArenaMain.Stone forColor) {
+        byte[] boardBuf = RustPlayer.encodeBoard(board);
+        byte expectedPlayer = switch (forColor) {
+            case BLUE -> 1;
+            case RED -> 0;
+        };
+        int winner = RustPlayer.rustBoardWinner(boardBuf);
+        return winner == expectedPlayer;
+    }
+
     @Override
     protected int play() {
         byte player = switch (this.myColor) {

rs-wrapper/Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-name = "rs-wrapper"
+name = "minmax_wrapper"
 version = "0.1.0"
 edition = "2021"
 

rs-wrapper/src/lib.rs

@@ -2,7 +2,7 @@ use jni::objects::{JClass, JObject, ReleaseMode};
 use jni::sys::{jbyte, jint};
 use jni::JNIEnv;
 use minmax::{connect4::board::Connect4, GamePlayer};
-use minmax::{Game, PerfectPlayer, Player};
+use minmax::{Game, PerfectPlayer, Player, State};
 
 /// We need to map the board.
 /// Rust:
@@ -28,7 +28,16 @@ fn map_idx(i: usize) -> usize {
     }
 }
 
-fn crate_board(java_board: &[i8]) -> Connect4 {
+unsafe fn create_board(env: JNIEnv<'_>, board: JObject<'_>) -> Connect4 {
+    let board_size = env.get_array_length(board.into_raw()).unwrap();
+    assert_eq!(board_size, 28);
+
+    let byte_array = env
+        .get_byte_array_elements(board.into_raw(), ReleaseMode::NoCopyBack)
+        .unwrap();
+
+    let java_board = unsafe { std::slice::from_raw_parts(byte_array.as_ptr().cast::<u8>(), 28) };
+
     let mut board = Connect4::new();
 
     for i in 0..28 {
@@ -37,7 +46,9 @@ fn crate_board(java_board: &[i8]) -> Connect4 {
             0 => Some(Player::X),
             1 => Some(Player::O),
             2 => None,
-            _ => unreachable!(),
+            _ => unreachable!(
+                "Java code passed an invalid value as the byte of the board: {java_int}"
+            ),
         };
 
         let rust_index = map_idx(i);
@@ -51,17 +62,8 @@ fn crate_board(java_board: &[i8]) -> Connect4 {
 // 0 -> RED -> X
 // 1 -> BLUE -> O
 // 2 -> empty
-pub fn wrap_player(env: JNIEnv<'_>, current_player: i8, board: JObject<'_>) -> i32 {
-    let board_size = env.get_array_length(board.into_raw()).unwrap();
-    assert_eq!(board_size, 28);
-
-    let byte_array = env
-        .get_byte_array_elements(board.into_raw(), ReleaseMode::NoCopyBack)
-        .unwrap();
-
-    let slice = unsafe { std::slice::from_raw_parts(byte_array.as_ptr() as *const _, 28) };
-
-    let mut board = crate_board(slice);
+pub fn play_move(env: JNIEnv<'_>, current_player: i8, board: JObject<'_>) -> i32 {
+    let mut board = unsafe { create_board(env, board) };
 
     let mut player = PerfectPlayer::new(false);
 
@@ -82,8 +84,18 @@ pub fn wrap_player(env: JNIEnv<'_>, current_player: i8, board: JObject<'_>) -> i
     java_idx
 }
 
-// This keeps Rust from "mangling" the name and making it unique for this
-// crate.
+fn board_winner(env: JNIEnv<'_>, board: JObject<'_>) -> i32 {
+    let board = unsafe { create_board(env, board) };
+
+    let state = board.result();
+    match state {
+        State::Draw => 2,
+        State::InProgress => 2,
+        State::Winner(Player::X) => 0,
+        State::Winner(Player::O) => 1,
+    }
+}
+
 #[no_mangle]
 pub extern "system" fn Java_ch_bbw_m411_connect4_RustPlayer_rustPlay(
     env: JNIEnv<'_>,
@@ -94,6 +106,18 @@ pub extern "system" fn Java_ch_bbw_m411_connect4_RustPlayer_rustPlay(
     player: jbyte,
     board: JObject<'_>,
 ) -> jint {
-    std::panic::catch_unwind(|| wrap_player(env, player, board))
+    std::panic::catch_unwind(|| play_move(env, player, board))
         .unwrap_or_else(|_| std::process::abort())
 }
+
+#[no_mangle]
+pub extern "system" fn Java_ch_bbw_m411_connect4_RustPlayer_rustBoardWinner(
+    env: JNIEnv<'_>,
+    // This is the class that owns our static method. It's not going to be used,
+    // but still must be present to match the expected signature of a static
+    // native method.
+    _: JClass<'_>,
+    board: JObject<'_>,
+) -> jint {
+    std::panic::catch_unwind(|| board_winner(env, board)).unwrap_or_else(|_| std::process::abort())
+}