Related issue: NETTY-251 Add support for HTTP trailing headers

* Added HttpChunkTrailer interface - need to write the default implementation
* HttpChunk.LAST_CHUNK implements HttpChunkTrailer

src/main/java/org/jboss/netty/handler/codec/http/HttpChunk.java

@@ -15,6 +15,10 @@
  */
 package org.jboss.netty.handler.codec.http;
 
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+
 import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.ChannelPipeline;
@@ -38,7 +42,7 @@ public interface HttpChunk {
     /**
      * The 'end of content' marker in chunked encoding.
      */
-    static HttpChunk LAST_CHUNK = new HttpChunk() {
+    static HttpChunkTrailer LAST_CHUNK = new HttpChunkTrailer() {
         public ChannelBuffer getContent() {
             return ChannelBuffers.EMPTY_BUFFER;
         }
@@ -46,6 +50,42 @@ public interface HttpChunk {
         public boolean isLast() {
             return true;
         }
+
+        public void addHeader(String name, String value) {
+            throw new IllegalStateException("read-only");
+        }
+
+        public void clearHeaders() {
+            // NOOP
+        }
+
+        public boolean containsHeader(String name) {
+            return false;
+        }
+
+        public String getHeader(String name) {
+            return null;
+        }
+
+        public Set<String> getHeaderNames() {
+            return Collections.emptySet();
+        }
+
+        public List<String> getHeaders(String name) {
+            return Collections.emptyList();
+        }
+
+        public void removeHeader(String name) {
+            // NOOP
+        }
+
+        public void setHeader(String name, String value) {
+            throw new IllegalStateException("read-only");
+        }
+
+        public void setHeader(String name, Iterable<String> values) {
+            throw new IllegalStateException("read-only");
+        }
     };
 
     /**

src/main/java/org/jboss/netty/handler/codec/http/HttpChunkTrailer.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2009 Red Hat, Inc.
+ *
+ * Red Hat 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 org.jboss.netty.handler.codec.http;
+
+import java.util.List;
+import java.util.Set;
+
+/**
+ * The last {@link HttpChunk} which has trailing headers.
+ *
+ * @author The Netty Project (netty-dev@lists.jboss.org)
+ * @author Trustin Lee (trustin@gmail.com)
+ * @version $Rev$, $Date$
+ */
+public interface HttpChunkTrailer extends HttpChunk {
+
+    /**
+     * Always returns {@code true}.
+     */
+    boolean isLast();
+
+    /**
+     * Returns the trailing header value with the specified header name.
+     * If there are more than one trailing header value for the specified
+     * header name, the first value is returned.
+     *
+     * @return the header value or {@code null} if there is no such header
+     *
+     */
+    String getHeader(String name);
+
+    /**
+     * Returns the trailing header values with the specified header name.
+     *
+     * @return the {@link List} of header values.  An empty list if there is no
+     *         such header.
+     */
+    List<String> getHeaders(String name);
+
+    /**
+     * Returns {@code true} if and only if there is a trailing header with
+     * the specified header name.
+     */
+    boolean containsHeader(String name);
+
+    /**
+     * Returns the {@link Set} of all trailing header names that this trailer
+     * contains.
+     */
+    Set<String> getHeaderNames();
+
+    /**
+     * Adds a new trailing header with the specified name and value.
+     */
+    void addHeader(String name, String value);
+
+    /**
+     * Sets a new trailing header with the specified name and value.
+     * If there is an existing trailing header with the same name, the existing
+     * one is removed.
+     */
+    void setHeader(String name, String value);
+
+    /**
+     * Sets a new trailing header with the specified name and values.
+     * If there is an existing trailing header with the same name, the existing
+     * one is removed.
+     */
+    void setHeader(String name, Iterable<String> values);
+
+    /**
+     * Removes the trailing header with the specified name.
+     */
+    void removeHeader(String name);
+
+    /**
+     * Removes all trailing headers from this trailer.
+     */
+    void clearHeaders();
+}