Fix setBytes on read-only ByteBuffer

Motivation:

The method setBytes did not work correctly because read-only ByteBuffer
does not allow access to its underlying array.

Modifications:

New case was added for ByteBuffer's that are not direct and do not have an array.
These must be handled by copying the data into a temporary array. Unit test was
added to test this case.

Result:

It is now possible to use read-only ByteBuffer as the source
for the setBytes method.

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

@@ -363,11 +363,21 @@ final class UnsafeByteBufUtil {
             // Copy from direct memory
             long srcAddress = PlatformDependent.directBufferAddress(src);
             PlatformDependent.copyMemory(srcAddress + src.position(), addr, src.remaining());
-        } else {
+            src.position(src.position() + length);
+        } else if (src.hasArray()) {
             // Copy from array
             PlatformDependent.copyMemory(src.array(), src.arrayOffset() + src.position(), addr, length);
+            src.position(src.position() + length);
+        } else {
+            ByteBuf tmpBuf = buf.alloc().heapBuffer(length);
+            try {
+                byte[] tmp = tmpBuf.array();
+                src.get(tmp, tmpBuf.arrayOffset(), length); // moves the src position too
+                PlatformDependent.copyMemory(tmp, 0, addr, length);
+            } finally {
+                tmpBuf.release();
+            }
         }
-        src.position(src.position() + length);
     }
 
     static void getBytes(AbstractByteBuf buf, long addr, int index, OutputStream out, int length) throws IOException {

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

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2015 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.buffer;
+
+import org.junit.Test;
+
+import java.nio.ByteBuffer;
+
+import static io.netty.util.internal.PlatformDependent.directBufferAddress;
+import static org.junit.Assert.assertArrayEquals;
+
+public class UnsafeByteBufUtilTest {
+
+    @Test
+    public void testSetBytesOnReadOnlyByteBuffer() throws Exception {
+        byte[] testData = new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+        int length = testData.length;
+
+        ByteBuffer readOnlyBuffer = ByteBuffer.wrap(testData).asReadOnlyBuffer();
+
+        UnpooledByteBufAllocator alloc = new UnpooledByteBufAllocator(true);
+        UnpooledDirectByteBuf targetBuffer = new UnpooledDirectByteBuf(alloc, length, length);
+
+        try {
+            UnsafeByteBufUtil.setBytes(targetBuffer, directBufferAddress(targetBuffer.nioBuffer()), 0, readOnlyBuffer);
+
+            byte[] check = new byte[length];
+            targetBuffer.getBytes(0, check, 0, length);
+
+            assertArrayEquals("The byte array's copy does not equal the original", testData, check);
+        } finally {
+            targetBuffer.release();
+        }
+    }
+}