Add ByteBuf.isReadOnly()

Motivation:

It is sometimes useful to determins if a buffer is read-only.

Modifications:

Add ByteBuf.isReadOnly()

Result:

One more feature

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

@@ -69,6 +69,11 @@ public abstract class AbstractByteBuf extends ByteBuf {
         this.maxCapacity = maxCapacity;
     }
 
+    @Override
+    public boolean isReadOnly() {
+        return false;
+    }
+
     @Override
     public int maxCapacity() {
         return maxCapacity;

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

@@ -70,6 +70,11 @@ public abstract class AbstractDerivedByteBuf extends AbstractByteBuf {
         return unwrap().release(decrement);
     }
 
+    @Override
+    public boolean isReadOnly() {
+        return unwrap().isReadOnly();
+    }
+
     @Override
     public ByteBuffer internalNioBuffer(int index, int length) {
         return nioBuffer(index, length);

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

@@ -295,6 +295,11 @@ public abstract class ByteBuf implements ReferenceCounted, Comparable<ByteBuf> {
      */
     public abstract boolean isDirect();
 
+    /**
+     * Returns {@code true} if and only if this buffer is read-only.
+     */
+    public abstract boolean isReadOnly();
+
     /**
      * Returns the {@code readerIndex} of this buffer.
      */

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

@@ -95,6 +95,11 @@ public final class EmptyByteBuf extends ByteBuf {
         return null;
     }
 
+    @Override
+    public boolean isReadOnly() {
+        return false;
+    }
+
     @Override
     public boolean isDirect() {
         return true;

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

@@ -50,6 +50,11 @@ public class ReadOnlyByteBuf extends AbstractDerivedByteBuf {
         setIndex(buffer.readerIndex(), buffer.writerIndex());
     }
 
+    @Override
+    public boolean isReadOnly() {
+        return true;
+    }
+
     @Override
     public boolean isWritable() {
         return false;

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

@@ -315,6 +315,11 @@ class ReadOnlyByteBufferBuf extends AbstractReferenceCountedByteBuf {
         return null;
     }
 
+    @Override
+    public boolean isReadOnly() {
+        return buffer.isReadOnly();
+    }
+
     @Override
     public boolean isDirect() {
         return buffer.isDirect();

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

@@ -92,6 +92,11 @@ public class SwappedByteBuf extends ByteBuf {
         return buf.maxCapacity();
     }
 
+    @Override
+    public boolean isReadOnly() {
+        return buf.isReadOnly();
+    }
+
     @Override
     public boolean isDirect() {
         return buf.isDirect();

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

@@ -93,6 +93,11 @@ class WrappedByteBuf extends ByteBuf {
         return buf;
     }
 
+    @Override
+    public boolean isReadOnly() {
+        return buf.isReadOnly();
+    }
+
     @Override
     public final boolean isDirect() {
         return buf.isDirect();

codec-http2/src/test/java/io/netty/handler/codec/http2/Http2FrameRoundtripTest.java

@@ -39,7 +39,6 @@ import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufAllocator;
 import io.netty.buffer.CompositeByteBuf;
 import io.netty.buffer.EmptyByteBuf;
-import io.netty.buffer.ReadOnlyByteBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelHandlerContext;
@@ -127,7 +126,7 @@ public class Http2FrameRoundtripTest {
             // Now verify that all of the reference counts are zero.
             for (ByteBuf buf : needReleasing) {
                 int expectedFinalRefCount = 0;
-                if (buf instanceof ReadOnlyByteBuf || buf instanceof EmptyByteBuf) {
+                if (buf.isReadOnly() || buf instanceof EmptyByteBuf) {
                     // Special case for when we're writing slices of the padding buffer.
                     expectedFinalRefCount = 1;
                 }

codec/src/main/java/io/netty/handler/codec/ReplayingDecoderByteBuf.java

@@ -88,6 +88,11 @@ final class ReplayingDecoderByteBuf extends ByteBuf {
         return buffer.alloc();
     }
 
+    @Override
+    public boolean isReadOnly() {
+        return false;
+    }
+
     @Override
     public boolean isDirect() {
         return buffer.isDirect();