java-topology/defects/love2d/unit/Love2dJoystickLookupTest.java

package unit;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Love2dJoystickLookupTest — CWE-407 love2d-0001
 *
 * Models JoystickModule::getJoystickFromID(int instanceid):
 *   slow() = O(n) linear scan of activeSticks vector (current defect)
 *   fast() = O(1) HashMap lookup keyed on instanceID (patch)
 *
 * Assert: slowOps > fastOps * Nx at N=64 joysticks.
 */
public class Love2dJoystickLookupTest {

    static class Joystick {
        final int instanceID;
        Joystick(int id) { this.instanceID = id; }
        int getInstanceID() { return instanceID; }
    }

    static long slowOps;
    static long fastOps;

    /**
     * slow: O(n) linear scan — models love2d getJoystickFromID defect.
     */
    static Joystick getJoystickFromIDSlow(List<Joystick> activeSticks, int instanceid) {
        for (Joystick stick : activeSticks) {
            slowOps++;
            if (stick.getInstanceID() == instanceid)
                return stick;
        }
        return null;
    }

    /**
     * fast: O(1) hash map lookup — models patched getJoystickFromID.
     */
    static Joystick getJoystickFromIDFast(Map<Integer, Joystick> sticksById, int instanceid) {
        fastOps++;
        return sticksById.get(instanceid);
    }

    public static void main(String[] args) {
        final int N = 64;         // number of active joysticks
        final int NX = 5;         // minimum required speedup factor
        final int EVENTS = 5000;  // SDL events dispatched per measurement

        // Build joystick list (instanceIDs 1..N)
        List<Joystick> activeSticks = new ArrayList<>();
        Map<Integer, Joystick> sticksById = new HashMap<>();
        for (int i = 1; i <= N; i++) {
            Joystick j = new Joystick(i);
            activeSticks.add(j);
            sticksById.put(i, j);
        }

        // Worst-case: always look up the last joystick (forces full scan for slow)
        int targetID = N;

        slowOps = 0;
        fastOps = 0;

        // Each event calls getJoystickFromID once (7 event types in love2d, simulate 1)
        for (int e = 0; e < EVENTS; e++) {
            getJoystickFromIDSlow(activeSticks, targetID);
        }
        long totalSlowOps = slowOps;

        for (int e = 0; e < EVENTS; e++) {
            getJoystickFromIDFast(sticksById, targetID);
        }
        long totalFastOps = fastOps;

        // Correctness check
        Joystick slowResult = getJoystickFromIDSlow(activeSticks, targetID);
        Joystick fastResult = getJoystickFromIDFast(sticksById, targetID);
        boolean correctnessOk = (slowResult != null && fastResult != null
            && slowResult.getInstanceID() == fastResult.getInstanceID());

        boolean speedupOk = totalSlowOps > totalFastOps * NX;

        System.out.printf("N=%d joysticks, target instanceID=%d, EVENTS=%d%n", N, targetID, EVENTS);
        System.out.printf("slow (linear) ops: %d%n", totalSlowOps);
        System.out.printf("fast (hashmap) ops: %d%n", totalFastOps);
        System.out.printf("speedup ratio: %.1fx (required >%dx)%n",
            (double) totalSlowOps / totalFastOps, NX);

        int passed = 0, total = 2;
        if (correctnessOk) {
            System.out.println("1/2 PASS correctness: both return same joystick");
            passed++;
        } else {
            System.out.printf("1/2 FAIL correctness: slow=%s fast=%s%n",
                slowResult == null ? "null" : slowResult.getInstanceID(),
                fastResult == null ? "null" : fastResult.getInstanceID());
        }
        if (speedupOk) {
            System.out.printf("2/2 PASS speedup: %d > %d * %d%n",
                totalSlowOps, totalFastOps, NX);
            passed++;
        } else {
            System.out.printf("2/2 FAIL speedup: %d not > %d * %d%n",
                totalSlowOps, totalFastOps, NX);
        }

        System.out.printf("%d/%d PASS%n", passed, total);
        if (passed < total) System.exit(1);
    }
}