[#441] Provide a better way to handle decoder failures

* Add DecodeResult that represents the result of decoding a message
* Add HttpObject which HttpMessage and HttpChunk extend.
** HttpObject has a property 'decodeResult'

codec-http/src/main/java/io/netty/handler/codec/http/DefaultHttpChunk.java

@@ -20,7 +20,7 @@ import io.netty.buffer.ByteBuf;
 /**
  * The default {@link HttpChunk} implementation.
  */
-public class DefaultHttpChunk implements HttpChunk {
+public class DefaultHttpChunk extends DefaultHttpObject implements HttpChunk {
 
     private ByteBuf content;
     private boolean last;

codec-http/src/main/java/io/netty/handler/codec/http/DefaultHttpChunkTrailer.java

@@ -25,7 +25,7 @@ import java.util.Set;
 /**
  * The default {@link HttpChunkTrailer} implementation.
  */
-public class DefaultHttpChunkTrailer implements HttpChunkTrailer {
+public class DefaultHttpChunkTrailer extends DefaultHttpObject implements HttpChunkTrailer {
 
     private final HttpHeaders headers = new HttpHeaders() {
         @Override

codec-http/src/main/java/io/netty/handler/codec/http/DefaultHttpMessage.java

@@ -26,7 +26,7 @@ import java.util.Set;
 /**
  * The default {@link HttpMessage} implementation.
  */
-public class DefaultHttpMessage implements HttpMessage {
+public class DefaultHttpMessage extends DefaultHttpObject implements HttpMessage {
 
     private final HttpHeaders headers = new HttpHeaders();
     private HttpVersion version;

codec-http/src/main/java/io/netty/handler/codec/http/DefaultHttpObject.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2012 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.handler.codec.http;
+
+import io.netty.handler.codec.DecodeResult;
+
+public class DefaultHttpObject implements HttpObject {
+
+    private DecodeResult decodeResult = DecodeResult.SUCCESS;
+
+    protected DefaultHttpObject() {
+        // Disallow direct instantiation
+    }
+
+    @Override
+    public DecodeResult getDecodeResult() {
+        return decodeResult;
+    }
+
+    @Override
+    public void setDecodeResult(DecodeResult result) {
+        if (result == null) {
+            throw new NullPointerException("result");
+        }
+        decodeResult = result;
+    }
+}

codec-http/src/main/java/io/netty/handler/codec/http/HttpChunk.java

@@ -18,6 +18,7 @@ package io.netty.handler.codec.http;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.channel.ChannelPipeline;
+import io.netty.handler.codec.DecodeResult;
 
 import java.util.Collections;
 import java.util.List;
@@ -33,7 +34,7 @@ import java.util.Set;
  * {@link ChannelPipeline}.
  * @apiviz.landmark
  */
-public interface HttpChunk {
+public interface HttpChunk extends HttpObject {
 
     /**
      * The 'end of content' marker in chunked encoding.
@@ -103,6 +104,16 @@ public interface HttpChunk {
         public void setHeader(String name, Iterable<?> values) {
             throw new IllegalStateException("read-only");
         }
+
+        @Override
+        public DecodeResult getDecodeResult() {
+            return DecodeResult.SUCCESS;
+        }
+
+        @Override
+        public void setDecodeResult(DecodeResult result) {
+            throw new IllegalStateException("read-only");
+        }
     };
 
     /**

codec-http/src/main/java/io/netty/handler/codec/http/HttpMessage.java

@@ -34,7 +34,7 @@ import java.util.Set;
  * @apiviz.landmark
  * @apiviz.has io.netty.handler.codec.http.HttpChunk oneway - - is followed by
  */
-public interface HttpMessage {
+public interface HttpMessage extends HttpObject {
 
     /**
      * Returns the value of a header with the specified name.  If there are

codec-http/src/main/java/io/netty/handler/codec/http/HttpObject.java

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2012 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.handler.codec.http;
+
+import io.netty.handler.codec.DecodeResult;
+
+public interface HttpObject {
+    DecodeResult getDecodeResult();
+    void setDecodeResult(DecodeResult result);
+}

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

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2012 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.handler.codec;
+
+public class DecodeResult {
+
+    public static final DecodeResult SUCCESS = new DecodeResult(false, null);
+
+    public static DecodeResult failure(Throwable cause) {
+        if (cause == null) {
+            throw new NullPointerException("cause");
+        }
+        return new DecodeResult(false, cause);
+    }
+
+    public static DecodeResult partialFailure(Throwable cause) {
+        if (cause == null) {
+            throw new NullPointerException("cause");
+        }
+        return new DecodeResult(true, cause);
+    }
+
+    private final boolean partial;
+    private final Throwable cause;
+
+    protected DecodeResult(boolean partial, Throwable cause) {
+        if (partial && cause == null) {
+            throw new IllegalArgumentException("successful result cannot be partial.");
+        }
+
+        this.partial = partial;
+        this.cause = cause;
+    }
+
+    public boolean isSuccess() {
+        return cause == null;
+    }
+
+    public boolean isPartial() {
+        return partial;
+    }
+
+    public Throwable cause() {
+        return cause;
+    }
+
+    @Override
+    public String toString() {
+        if (isSuccess()) {
+            return "success";
+        }
+
+        String cause = cause().toString();
+        StringBuilder buf = new StringBuilder(cause.length() + 17);
+        if (isPartial()) {
+            buf.append("partial_");
+        }
+        buf.append("failure(");
+        buf.append(cause);
+        buf.append(')');
+
+        return buf.toString();
+    }
+}