Throw NoSuchBufferException instead of returning null

- Exception in this case makes a user less confusing
- To reduce the overhead of filling the stack trace,
  NoSuchBufferException has a public pre-constructed instance.
  - This is necessary because codec framework sometimes need to support
    both type of outbound buffers.
- Fixed a bug where SpdyFrameEncoder did not handle ping messages
- Reduced memory copy in codec embedder (EmbeddedChannel)

codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyFrameEncoder.java

@@ -84,7 +84,8 @@ public class SpdyFrameEncoder extends MessageToStreamEncoder<Object> {
                msg instanceof SpdySettingsFrame ||
                msg instanceof SpdyNoOpFrame ||
                msg instanceof SpdyGoAwayFrame ||
-               msg instanceof SpdyHeadersFrame;
+               msg instanceof SpdyHeadersFrame ||
+               msg instanceof SpdyPingFrame;
     }
 
     @Override

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

@@ -2,8 +2,7 @@ package io.netty.handler.codec;
 
 import io.netty.buffer.ChannelBuffer;
 import io.netty.channel.ChannelHandlerContext;
-
+import io.netty.channel.NoSuchBufferException;
-import java.util.Queue;
 
 class CodecUtil {
 
@@ -33,34 +32,32 @@ class CodecUtil {
         }
 
         if (inbound) {
-            Queue<Object> dst = ctx.nextInboundMessageBuffer();
+            try {
-            if (dst != null) {
+                ctx.nextInboundMessageBuffer().add(msg);
-                dst.add(msg);
                 return true;
-            } else if (msg instanceof ChannelBuffer) {
+            } catch (NoSuchBufferException e) {
-                ChannelBuffer altDst = ctx.nextInboundByteBuffer();
+                if (msg instanceof ChannelBuffer) {
-                ChannelBuffer src = (ChannelBuffer) msg;
+                    ChannelBuffer altDst = ctx.nextInboundByteBuffer();
-                if (altDst != null) {
+                    ChannelBuffer src = (ChannelBuffer) msg;
                     altDst.writeBytes(src, src.readerIndex(), src.readableBytes());
                     return true;
                 }
             }
         } else {
-            Queue<Object> dst = ctx.nextOutboundMessageBuffer();
+            try {
-            if (dst != null) {
+                ctx.nextOutboundMessageBuffer().add(msg);
-                dst.add(msg);
                 return true;
-            } else if (msg instanceof ChannelBuffer) {
+            } catch (NoSuchBufferException e) {
-                ChannelBuffer altDst = ctx.nextOutboundByteBuffer();
+                if (msg instanceof ChannelBuffer) {
-                ChannelBuffer src = (ChannelBuffer) msg;
+                    ChannelBuffer altDst = ctx.nextOutboundByteBuffer();
-                if (altDst != null) {
+                    ChannelBuffer src = (ChannelBuffer) msg;
                     altDst.writeBytes(src, src.readerIndex(), src.readableBytes());
                     return true;
                 }
             }
         }
 
-        throw new IllegalStateException("no suitable destination buffer found");
+        throw new NoSuchBufferException();
     }
 
     private CodecUtil() {

codec/src/main/java/io/netty/handler/codec/embedder/EmbeddedChannel.java

@@ -16,6 +16,7 @@
 package io.netty.handler.codec.embedder;
 
 import io.netty.buffer.ChannelBuffer;
+import io.netty.buffer.ChannelBuffers;
 import io.netty.channel.AbstractChannel;
 import io.netty.channel.ChannelBufferHolder;
 import io.netty.channel.ChannelBufferHolders;
@@ -39,7 +40,7 @@ class EmbeddedChannel extends AbstractChannel {
     EmbeddedChannel(Queue<Object> productQueue) {
         super(null, null);
         this.productQueue = productQueue;
-        firstOut = ChannelBufferHolders.catchAllBuffer();
+        firstOut = ChannelBufferHolders.catchAllBuffer(productQueue, ChannelBuffers.dynamicBuffer());
     }
 
     @Override
@@ -111,11 +112,7 @@ class EmbeddedChannel extends AbstractChannel {
             productQueue.add(byteBuf.readBytes(byteBufLen));
             byteBuf.clear();
         }
-        Queue<Object> msgBuf = buf.messageBuffer();
+        // We do nothing for message buffer because it's actually productQueue.
-        if (!msgBuf.isEmpty()) {
-            productQueue.addAll(msgBuf);
-            msgBuf.clear();
-        }
     }
 
     @Override

transport/src/main/java/io/netty/channel/ChannelBufferHolder.java

@@ -59,9 +59,21 @@ public final class ChannelBufferHolder<E> {
         case 0:
             return msgBuf != null;
         case 1:
-            return ctx.nextInboundMessageBuffer() != null;
+            // XXX: Should we introduce hasNext(Inbound|Outbound)(Message|Byte)Buffer()
+            //      just because of this?
+            try {
+                ctx.nextInboundMessageBuffer();
+                return true;
+            } catch (NoSuchBufferException e) {
+                return false;
+            }
         case 2:
-            return ctx.nextOutboundMessageBuffer() != null;
+            try {
+                ctx.nextOutboundMessageBuffer();
+                return true;
+            } catch (NoSuchBufferException e) {
+                return false;
+            }
         default:
             throw new Error();
         }
@@ -72,9 +84,19 @@ public final class ChannelBufferHolder<E> {
         case 0:
             return byteBuf != null;
         case 1:
-            return ctx.nextInboundByteBuffer() != null;
+            try {
+                ctx.nextInboundByteBuffer();
+                return true;
+            } catch (NoSuchBufferException e) {
+                return false;
+            }
         case 2:
-            return ctx.nextOutboundByteBuffer() != null;
+            try {
+                ctx.nextOutboundByteBuffer();
+                return true;
+            } catch (NoSuchBufferException e) {
+                return false;
+            }
         default:
             throw new Error();
         }
@@ -84,7 +106,7 @@ public final class ChannelBufferHolder<E> {
         switch (bypassDirection) {
         case 0:
             if (msgBuf == null) {
-                throw new IllegalStateException("does not have a message buffer");
+                throw new NoSuchBufferException();
             }
             return msgBuf;
         case 1:
@@ -100,7 +122,7 @@ public final class ChannelBufferHolder<E> {
         switch (bypassDirection) {
         case 0:
             if (byteBuf == null) {
-                throw new IllegalStateException("does not have a byte buffer");
+                throw new NoSuchBufferException();
             }
             return byteBuf;
         case 1:

transport/src/main/java/io/netty/channel/DefaultChannelPipeline.java

@@ -1157,7 +1157,7 @@ public class DefaultChannelPipeline implements ChannelPipeline {
             for (;;) {
                 ctx = nextInboundContext(ctx.next);
                 if (ctx == null) {
-                    return null;
+                    throw NoSuchBufferException.INSTANCE;
                 }
                 ChannelBufferHolder<Object> nextIn = ctx.inbound();
                 if (nextIn.hasByteBuffer()) {
@@ -1172,7 +1172,7 @@ public class DefaultChannelPipeline implements ChannelPipeline {
             for (;;) {
                 ctx = nextInboundContext(ctx.next);
                 if (ctx == null) {
-                    return null;
+                    throw NoSuchBufferException.INSTANCE;
                 }
                 ChannelBufferHolder<Object> nextIn = ctx.inbound();
                 if (nextIn.hasMessageBuffer()) {
@@ -1191,7 +1191,7 @@ public class DefaultChannelPipeline implements ChannelPipeline {
                     if (lastOut.hasByteBuffer()) {
                         return lastOut.byteBuffer();
                     } else {
-                        return null;
+                        throw NoSuchBufferException.INSTANCE;
                     }
                 }
                 ChannelBufferHolder<Object> nextOut = ctx.outbound();
@@ -1211,7 +1211,7 @@ public class DefaultChannelPipeline implements ChannelPipeline {
                     if (lastOut.hasMessageBuffer()) {
                         return lastOut.messageBuffer();
                     } else {
-                        return null;
+                        throw NoSuchBufferException.INSTANCE;
                     }
                 }
                 ChannelBufferHolder<Object> nextOut = ctx.outbound();

transport/src/main/java/io/netty/channel/NoSuchBufferException.java

@@ -0,0 +1,36 @@
+package io.netty.channel;
+
+/**
+ * A {@link ChannelPipelineException} which is raised if an inbound or outbound buffer of
+ * the expected type is not found while transferring data between {@link ChannelHandler}s.
+ * This exception is usually triggered by an incorrectly configured {@link ChannelPipeline}.
+ */
+public class NoSuchBufferException extends ChannelPipelineException {
+
+    private static final String DEFAULT_MESSAGE =
+            "Could not find a suitable destination buffer.  Double-check if the pipeline is " +
+            "configured correctly and its handlers works as expected.";
+    public static final NoSuchBufferException INSTANCE = new NoSuchBufferException();
+
+    static {
+        INSTANCE.setStackTrace(new StackTraceElement[0]);
+    }
+
+    private static final long serialVersionUID = -131650785896627090L;
+
+    public NoSuchBufferException() {
+        this(DEFAULT_MESSAGE);
+    }
+
+    public NoSuchBufferException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public NoSuchBufferException(String message) {
+        super(message);
+    }
+
+    public NoSuchBufferException(Throwable cause) {
+        super(cause);
+    }
+}