package com.js.kbt.socket;

import java.nio.ByteOrder;
import java.nio.charset.Charset;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.DecoderException;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;

public class MyProtocolDecoder extends LengthFieldBasedFrameDecoder {
	private static final String HEXES = "0123456789ABCDEF";
    private static final int HEADER_SIZE = 4;

    /**
     *
     * @param maxFrameLength  帧的最大长度
     * @param lengthFieldOffset length字段偏移的地址
     * @param lengthFieldLength length字段所占的字节长
     * @param lengthAdjustment 修改帧数据长度字段中定义的值，可以为负数 因为有时候我们习惯把头部记入长度,若为负数,则说明要推后多少个字段
     * @param initialBytesToStrip 解析时候跳过多少个长度
     * @param failFast 为true，当frame长度超过maxFrameLength时立即报TooLongFrameException异常，为false，读取完整个帧再报异
     */

    public MyProtocolDecoder(int maxFrameLength, int lengthFieldOffset, int lengthFieldLength, int lengthAdjustment, int initialBytesToStrip, boolean failFast) {

        super(maxFrameLength, lengthFieldOffset, lengthFieldLength, lengthAdjustment, initialBytesToStrip, failFast);

    }
   
    protected long getUnadjustedFrameLength(ByteBuf buf, int offset, int length, ByteOrder order) {
            buf = buf.order(order);
            long frameLength;
            byte b1 = buf.getByte(offset);
            byte b2 = buf.getByte(offset + 1);
            StringBuilder hex = new StringBuilder();
            String s1 = hex.append(HEXES.charAt((b2 & 0xF0) >> 4)).append(HEXES.charAt((b2 & 0x0F)))
            		.append(HEXES.charAt((b1 & 0xF0) >> 4)).append(HEXES.charAt((b1 & 0x0F))).toString();
            frameLength = Integer.parseInt(s1, 16) - 4;//去掉头部的FAAF0000四位
            System.out.println("getUnadjustedFrameLength解析长度："+frameLength);
            return frameLength;
        }
    @Override
    protected Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
    	System.out.println("解析长度decode：");
        //在这里调用父类的方法,实现指得到想要的部分,我在这里全部都要,也可以只要body部分
        in = (ByteBuf) super.decode(ctx,in);  

        if(in == null){
            return null;
        }
        if(in.readableBytes()<HEADER_SIZE){
            throw new Exception("字节数不足");
        }
//        byte fa = in.readByte();
//        byte af = in.readByte();
        
//        byte b1 = in.readByte();
//        byte b2 = in.readByte();
//        //读取length字段
//        StringBuilder hex = new StringBuilder();
//        String s1 = hex.append(HEXES.charAt((b2 & 0xF0) >> 4)).append(HEXES.charAt((b2 & 0x0F)))
//        		.append(HEXES.charAt((b1 & 0xF0) >> 4)).append(HEXES.charAt((b1 & 0x0F))).toString();
//        
//        int length = Integer.parseInt(s1, 16);
//        System.out.println("解析长度："+length);
//        if(in.readableBytes()!=length){
//            throw new Exception("标记的长度不符合实际长度");
//        }
        //读取body
        byte []bytes = new byte[in.readableBytes()];
        in.readBytes(bytes);

        return bytes;
    }
}