Make sure we can get memory addresses before we think about natives.

native/src/main/java/com/velocitypowered/natives/Native.java

@@ -0,0 +1,5 @@
+package com.velocitypowered.natives;
+
+public interface Native {
+  boolean isNative();
+}

native/src/main/java/com/velocitypowered/natives/compression/JavaVelocityCompressor.java

@@ -62,4 +62,9 @@ public class JavaVelocityCompressor implements VelocityCompressor {
   private void ensureNotDisposed() {
     Preconditions.checkState(!disposed, "Object already disposed");
   }
+
+  @Override
+  public boolean isNative() {
+    return false;
+  }
 }

native/src/main/java/com/velocitypowered/natives/compression/NativeVelocityCompressor.java

@@ -78,4 +78,9 @@ public class NativeVelocityCompressor implements VelocityCompressor {
     }
     disposed = true;
   }
+
+  @Override
+  public boolean isNative() {
+    return true;
+  }
 }

native/src/main/java/com/velocitypowered/natives/compression/VelocityCompressor.java

@@ -1,13 +1,14 @@
 package com.velocitypowered.natives.compression;
 
 import com.velocitypowered.natives.Disposable;
+import com.velocitypowered.natives.Native;
 import io.netty.buffer.ByteBuf;
 import java.util.zip.DataFormatException;
 
 /**
  * Provides an interface to inflate and deflate {@link ByteBuf}s using zlib.
  */
-public interface VelocityCompressor extends Disposable {
+public interface VelocityCompressor extends Disposable, Native {
   void inflate(ByteBuf source, ByteBuf destination) throws DataFormatException;
 
   void deflate(ByteBuf source, ByteBuf destination) throws DataFormatException;

native/src/main/java/com/velocitypowered/natives/encryption/JavaVelocityCipher.java

@@ -79,4 +79,9 @@ public class JavaVelocityCipher implements VelocityCipher {
   private void ensureNotDisposed() {
     Preconditions.checkState(!disposed, "Object already disposed");
   }
+
+  @Override
+  public boolean isNative() {
+    return false;
+  }
 }

native/src/main/java/com/velocitypowered/natives/encryption/NativeVelocityCipher.java

@@ -1,5 +1,6 @@
 package com.velocitypowered.natives.encryption;
 
+import com.google.common.base.Preconditions;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandlerContext;
 import java.security.GeneralSecurityException;
@@ -32,6 +33,7 @@ public class NativeVelocityCipher implements VelocityCipher {
 
   @Override
   public void process(ByteBuf source, ByteBuf destination) throws ShortBufferException {
+    ensureNotDisposed();
     source.memoryAddress();
     destination.memoryAddress();
 
@@ -65,4 +67,13 @@ public class NativeVelocityCipher implements VelocityCipher {
     }
     disposed = true;
   }
+
+  private void ensureNotDisposed() {
+    Preconditions.checkState(!disposed, "Object already disposed");
+  }
+
+  @Override
+  public boolean isNative() {
+    return true;
+  }
 }

native/src/main/java/com/velocitypowered/natives/encryption/VelocityCipher.java

@@ -1,11 +1,12 @@
 package com.velocitypowered.natives.encryption;
 
 import com.velocitypowered.natives.Disposable;
+import com.velocitypowered.natives.Native;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandlerContext;
 import javax.crypto.ShortBufferException;
 
-public interface VelocityCipher extends Disposable {
+public interface VelocityCipher extends Disposable, Native {
 
   void process(ByteBuf source, ByteBuf destination) throws ShortBufferException;
 

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

@@ -0,0 +1,33 @@
+package com.velocitypowered.natives.util;
+
+import com.velocitypowered.natives.Native;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
+
+public class MoreByteBufUtils {
+  private MoreByteBufUtils() {
+    throw new AssertionError();
+  }
+
+  /**
+   * Ensures the {@code buf} will work with the specified {@code nativeThing}. After this function
+   * is called, you should decrement the reference count on the {@code buf} with
+   * {@link ByteBuf#release()}.
+   *
+   * @param alloc the {@link ByteBufAllocator} to use
+   * @param nativeStuff the native we are working with
+   * @param buf the buffer we are working with
+   * @return a buffer compatible with the native
+   */
+  public static ByteBuf ensureCompatible(ByteBufAllocator alloc, Native nativeStuff, ByteBuf buf) {
+    if (!nativeStuff.isNative() || buf.hasMemoryAddress()) {
+      // Will always work in either case.
+      return buf.retain();
+    }
+
+    // It's not, so we must make a memory copy.
+    ByteBuf newBuf = alloc.directBuffer();
+    newBuf.writeBytes(buf);
+    return newBuf;
+  }
+}

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

@@ -1,18 +1,32 @@
 package com.velocitypowered.natives.util;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
 import java.util.function.BooleanSupplier;
 
 public class NativeConstraints {
   private static final boolean NATIVES_ENABLED = !Boolean.getBoolean("velocity.natives-disabled");
+  private static final boolean CAN_GET_MEMORYADDRESS;
+
+  static {
+    ByteBuf test = Unpooled.directBuffer();
+    try {
+      CAN_GET_MEMORYADDRESS = test.hasMemoryAddress();
+    } finally {
+      test.release();
+    }
+  }
 
   static final BooleanSupplier MACOS = () -> {
     return NATIVES_ENABLED
+        && CAN_GET_MEMORYADDRESS
         && System.getProperty("os.name", "").equalsIgnoreCase("Mac OS X")
         && System.getProperty("os.arch").equals("x86_64");
   };
 
   static final BooleanSupplier LINUX = () -> {
     return NATIVES_ENABLED
+        && CAN_GET_MEMORYADDRESS
         && System.getProperty("os.name", "").equalsIgnoreCase("Linux")
         && System.getProperty("os.arch").equals("amd64");
   };