CompositeByteBuf.isDirect() should return true if its only backed by direct buffers

buffer/src/main/java/io/netty/buffer/CompositeByteBuf.java

@@ -430,10 +430,16 @@ public class CompositeByteBuf extends AbstractReferenceCountedByteBuf {
 
     @Override
     public boolean isDirect() {
-        if (components.size() == 1) {
-            return components.get(0).buf.isDirect();
+        int size = components.size();
+        if (size == 0) {
+            return false;
         }
-        return false;
+        for (int i = 0; i < size; i++) {
+           if (!components.get(i).buf.isDirect()) {
+               return false;
+           }
+        }
+        return true;
     }
 
     @Override

buffer/src/test/java/io/netty/buffer/AbstractCompositeByteBufTest.java

@@ -776,4 +776,20 @@ public abstract class AbstractCompositeByteBufTest extends AbstractByteBufTest {
     public void testInternalNioBuffer() {
         // ignore
     }
+
+    @Test
+    public void testisDirectMultipleBufs() {
+        CompositeByteBuf buf = freeLater(compositeBuffer());
+        assertFalse(buf.isDirect());
+
+        buf.addComponent(directBuffer().writeByte(1));
+
+        assertTrue(buf.isDirect());
+        buf.addComponent(directBuffer().writeByte(1));
+        assertTrue(buf.isDirect());
+
+        buf.addComponent(buffer().writeByte(1));
+        assertFalse(buf.isDirect());
+
+    }
 }