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/*
 * 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;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelDuplexHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundByteHandler;
import io.netty.channel.ChannelOutboundByteHandler;
import io.netty.channel.ChannelPromise;

/**
 * A Codec for on-the-fly encoding/decoding of bytes.
 *
 * This can be thought of as a combination of {@link ByteToByteDecoder} and {@link ByteToByteEncoder}.
 *
 * Here is an example of a {@link ByteToByteCodec} which just square {@link Integer} read from a {@link ByteBuf}.
 *  *     public class SquareCodec extends {@link ByteToByteCodec} {
 *         {@code @Override}
 *         public void decode({@link ChannelHandlerContext} ctx, {@link ByteBuf} in, {@link ByteBuf} out)
 *                 throws {@link Exception} {
 *             if (in.readableBytes() < 4) {
 *                 return;
 *             }
 *             int value = in.readInt();
 *             out.writeInt(value * value);
 *         }
 *
 *         {@code @Overrride}
 *         public void encode({@link ChannelHandlerContext} ctx, {@link ByteBuf} in, {@link ByteBuf} out)
 *                 throws {@link Exception} {
 *             if (in.readableBytes() < 4) {
 *                 return;
 *             }
 *             int value = in.readInt();
 *             out.writeInt(value / value);
 *         }
 *     }
 * 
 */
public abstract class ByteToByteCodec
        extends ChannelDuplexHandler
        implements ChannelInboundByteHandler, ChannelOutboundByteHandler {

    private final ByteToByteEncoder encoder = new ByteToByteEncoder() {
        @Override
        protected void encode(
                ChannelHandlerContext ctx,
                ByteBuf in, ByteBuf out) throws Exception {
            ByteToByteCodec.this.encode(ctx, in, out);
        }
    };

    private final ByteToByteDecoder decoder = new ByteToByteDecoder() {
        @Override
        protected void decode(ChannelHandlerContext ctx, ByteBuf in, ByteBuf out) throws Exception {
            ByteToByteCodec.this.decode(ctx, in, out);
        }

        @Override
        protected void decodeLast(ChannelHandlerContext ctx, ByteBuf in, ByteBuf out) throws Exception {
            ByteToByteCodec.this.decodeLast(ctx, in, out);
        }
    };

    @Override
    public ByteBuf newInboundBuffer(ChannelHandlerContext ctx) throws Exception {
        return decoder.newInboundBuffer(ctx);
    }

    @Override
    public void inboundBufferUpdated(ChannelHandlerContext ctx) throws Exception {
        decoder.inboundBufferUpdated(ctx);
    }

    @Override
    public ByteBuf newOutboundBuffer(ChannelHandlerContext ctx) throws Exception {
        return encoder.newOutboundBuffer(ctx);
    }

    @Override
    public void flush(
            ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
        encoder.flush(ctx, promise);
    }

    @Override
    public void discardInboundReadBytes(ChannelHandlerContext ctx) throws Exception {
        decoder.discardInboundReadBytes(ctx);
    }

    @Override
    public void discardOutboundReadBytes(ChannelHandlerContext ctx) throws Exception {
        encoder.discardOutboundReadBytes(ctx);
    }

    @Override
    public void freeInboundBuffer(ChannelHandlerContext ctx) throws Exception {
        decoder.freeInboundBuffer(ctx);
    }

    @Override
    public void freeOutboundBuffer(ChannelHandlerContext ctx) throws Exception {
        encoder.freeOutboundBuffer(ctx);
    }

    /**
     * @see {@link ByteToByteEncoder#encode(ChannelHandlerContext, ByteBuf, ByteBuf)}
     */
    protected abstract void encode(ChannelHandlerContext ctx, ByteBuf in, ByteBuf out) throws Exception;

    /**
     * @see {@link ByteToByteDecoder#decode(ChannelHandlerContext, ByteBuf, ByteBuf)}
     */
    protected abstract void decode(ChannelHandlerContext ctx, ByteBuf in, ByteBuf out) throws Exception;

    /**
     * @see {@link ByteToByteDecoder#decodeLast(ChannelHandlerContext, ByteBuf, ByteBuf)}
     */
    protected void decodeLast(ChannelHandlerContext ctx, ByteBuf in, ByteBuf out) throws Exception {
        decode(ctx, in, out);
    }
}