Checker Framework integration (#126)

native/build.gradle

@@ -2,9 +2,13 @@ plugins {
     id 'java'
 }
 
+apply from: '../gradle/checkerframework.gradle'
+
 dependencies {
     compile "com.google.guava:guava:${guavaVersion}"
     compile "io.netty:netty-buffer:${nettyVersion}"
+    compile "org.checkerframework:checker-qual:${checkerFrameworkVersion}"
+
     testCompile "org.junit.jupiter:junit-jupiter-api:${junitVersion}"
     testCompile "org.junit.jupiter:junit-jupiter-engine:${junitVersion}"
 }

native/src/main/java/com/velocitypowered/natives/util/NativeCodeLoader.java

@@ -1,88 +1,64 @@
 package com.velocitypowered.natives.util;
 
-import com.google.common.collect.ImmutableList;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.List;
 import java.util.function.BooleanSupplier;
 import java.util.function.Supplier;
 
-public class NativeCodeLoader<T> implements Supplier<T> {
-    private final List<Variant<T>> variants;
-    private volatile Variant<T> selected;
+public final class NativeCodeLoader<T> implements Supplier<T> {
+    private final Variant<T> selected;
 
-    public NativeCodeLoader(List<Variant<T>> variants) {
-        this.variants = ImmutableList.copyOf(variants);
+    NativeCodeLoader(List<Variant<T>> variants) {
+        this.selected = getVariant(variants);
     }
 
     @Override
     public T get() {
-        return tryLoad().object;
+        return selected.object;
     }
 
-    private Variant<T> tryLoad() {
-        if (selected != null) {
-            return selected;
-        }
-
-        synchronized (this) {
-            if (selected != null) {
-                return selected;
+    private static <T> Variant<T> getVariant(List<Variant<T>> variants) {
+        for (Variant<T> variant : variants) {
+            T got = variant.get();
+            if (got == null) {
+                continue;
             }
-
-            for (Variant<T> variant : variants) {
-                T got = variant.get();
-                if (got == null) {
-                    continue;
-                }
-                selected = variant;
-                return selected;
-            }
-            throw new IllegalArgumentException("Can't find any suitable variants");
+            return variant;
         }
+        throw new IllegalArgumentException("Can't find any suitable variants");
     }
 
     public String getLoadedVariant() {
-        return tryLoad().name;
+        return selected.name;
     }
 
     static class Variant<T> {
-        private volatile boolean available;
+        private Status status;
         private final Runnable setup;
         private final String name;
         private final T object;
-        private volatile boolean hasBeenSetup = false;
 
-        Variant(BooleanSupplier available, Runnable setup, String name, T object) {
-            this.available = available.getAsBoolean();
+        Variant(BooleanSupplier possiblyAvailable, Runnable setup, String name, T object) {
+            this.status = possiblyAvailable.getAsBoolean() ? Status.POSSIBLY_AVAILABLE : Status.NOT_AVAILABLE;
             this.setup = setup;
             this.name = name;
             this.object = object;
         }
 
-        public T get() {
-            if (!available) {
+        public @Nullable T get() {
+            if (status == Status.NOT_AVAILABLE || status == Status.SETUP_FAILURE) {
                 return null;
             }
 
             // Make sure setup happens only once
-            if (!hasBeenSetup) {
-                synchronized (this) {
-                    // We change availability if need be below, may as well check it again here for sanity.
-                    if (!available) {
-                        return null;
-                    }
-
-                    // Okay, now try the setup if we haven't done so yet.
-                    if (!hasBeenSetup) {
-                        try {
-                            setup.run();
-                            hasBeenSetup = true;
-                            return object;
-                        } catch (Exception e) {
-                            available = false;
-                            return null;
-                        }
-                    }
+            if (status == Status.POSSIBLY_AVAILABLE) {
+                try {
+                    setup.run();
+                    status = Status.SETUP;
+                } catch (Exception e) {
+                    status = Status.SETUP_FAILURE;
+                    return null;
                 }
             }
 
@@ -90,9 +66,16 @@ public class NativeCodeLoader<T> implements Supplier<T> {
         }
     }
 
-    static final BooleanSupplier MACOS = () -> System.getProperty("os.name").equalsIgnoreCase("Mac OS X") &&
+    private enum Status {
+        NOT_AVAILABLE,
+        POSSIBLY_AVAILABLE,
+        SETUP,
+        SETUP_FAILURE
+    }
+
+    static final BooleanSupplier MACOS = () -> System.getProperty("os.name", "").equalsIgnoreCase("Mac OS X") &&
             System.getProperty("os.arch").equals("x86_64");
-    static final BooleanSupplier LINUX = () -> System.getProperties().getProperty("os.name").equalsIgnoreCase("Linux") &&
+    static final BooleanSupplier LINUX = () -> System.getProperties().getProperty("os.name", "").equalsIgnoreCase("Linux") &&
             System.getProperty("os.arch").equals("amd64");
     static final BooleanSupplier ALWAYS = () -> true;
 }

native/src/main/java/com/velocitypowered/natives/util/Natives.java

@@ -8,6 +8,7 @@ import com.velocitypowered.natives.encryption.JavaVelocityCipher;
 import com.velocitypowered.natives.encryption.VelocityCipherFactory;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
@@ -21,7 +22,12 @@ public class Natives {
         return () -> {
             try {
                 Path tempFile = Files.createTempFile("native-", path.substring(path.lastIndexOf('.')));
-                Files.copy(Natives.class.getResourceAsStream(path), tempFile, StandardCopyOption.REPLACE_EXISTING);
+                InputStream nativeLib = Natives.class.getResourceAsStream(path);
+                if (nativeLib == null) {
+                    throw new IllegalStateException("Native library " + path + " not found.");
+                }
+
+                Files.copy(nativeLib, tempFile, StandardCopyOption.REPLACE_EXISTING);
                 Runtime.getRuntime().addShutdownHook(new Thread(() -> {
                     try {
                         Files.deleteIfExists(tempFile);