From 5f15d91c4158897a55a860878e67b7a4ca17bc9a Mon Sep 17 00:00:00 2001
From: Trustin Lee <trustin@gmail.com>
Date: Wed, 7 Jan 2009 02:14:12 +0000
Subject: [PATCH] Added LengthFieldPrepender to prepend a length field easily

---
 .../codec/frame/LengthFieldPrepender.java     | 82 +++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 src/main/java/org/jboss/netty/handler/codec/frame/LengthFieldPrepender.java

diff --git a/src/main/java/org/jboss/netty/handler/codec/frame/LengthFieldPrepender.java b/src/main/java/org/jboss/netty/handler/codec/frame/LengthFieldPrepender.java
new file mode 100644
index 0000000000..2cedae74b6
--- /dev/null
+++ b/src/main/java/org/jboss/netty/handler/codec/frame/LengthFieldPrepender.java
@@ -0,0 +1,82 @@
+/*
+ * JBoss, Home of Professional Open Source
+ *
+ * Copyright 2009, Red Hat Middleware LLC, and individual contributors
+ * by the @author tags. See the COPYRIGHT.txt in the distribution for a
+ * full listing of individual contributors.
+ *
+ * This is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this software; if not, write to the Free
+ * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
+ */
+package org.jboss.netty.handler.codec.frame;
+
+import static org.jboss.netty.buffer.ChannelBuffers.*;
+
+import org.jboss.netty.buffer.ChannelBuffer;
+import org.jboss.netty.channel.Channel;
+import org.jboss.netty.channel.ChannelHandlerContext;
+import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;
+
+/**
+ * TODO Documentation
+ *
+ * @author The Netty Project (netty-dev@lists.jboss.org)
+ * @author Trustin Lee (tlee@redhat.com)
+ * @version $Rev$, $Date$
+ */
+public class LengthFieldPrepender extends OneToOneEncoder {
+
+    private final int lengthFieldLength;
+
+    public LengthFieldPrepender(int lengthFieldLength) {
+        if (lengthFieldLength != 1 && lengthFieldLength != 2 &&
+            lengthFieldLength != 3 && lengthFieldLength != 4 &&
+            lengthFieldLength != 8) {
+            throw new IllegalArgumentException(
+                    "lengthFieldLength must be either 1, 2, 3, 4, or 8: " +
+                    lengthFieldLength);
+        }
+
+        this.lengthFieldLength = lengthFieldLength;
+    }
+
+    @Override
+    protected Object encode(
+            ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
+        ChannelBuffer header = channel.getConfig().getBufferFactory().getBuffer(lengthFieldLength);
+        ChannelBuffer body = (ChannelBuffer) msg;
+
+        switch (lengthFieldLength) {
+        case 1:
+            header.writeByte((byte) body.readableBytes());
+            break;
+        case 2:
+            header.writeShort((short) body.readableBytes());
+            break;
+        case 3:
+            header.writeMedium(body.readableBytes());
+            break;
+        case 4:
+            header.writeInt(body.readableBytes());
+            break;
+        case 8:
+            header.writeLong(body.readableBytes());
+            break;
+        default:
+            throw new Error("should not reach here");
+        }
+        return wrappedBuffer(header, body);
+    }
+}
\ No newline at end of file