min-dev-java/src/main/java/component/MutableDangerousField.java

package component;

import encoding.*;

/*
 * @Author: Wang Feng
 * @Description: 表示一个MIN包格式中的可变非受保护区
 * @Version: 1.0.0
 * @Date: 20:34 2021/3/9
 * @Copyright: MIN-Group；国家重大科技基础设施——未来网络北大实验室；深圳市信息论与未来网络重点实验室
 */
public class MutableDangerousField implements TlvComponentBase, IEncodingAble {
    private ElementContainer blocks= new ElementContainer();

    public MutableDangerousField(){
    }

    /**
     * 往可变非受保护区添加一个Block
     *
     * @param block
     */
    public void addBlock(Block block) {
        blocks.addElement(block);
    }

    /**
     * 获取可变非受保护区指定位置的 Block
     *
     * @return
     */
    public Block getBlock(int index) throws ComponentException {
        try {
            return this.blocks.getBlock(index);
        } catch (BlockException e) {
            throw new ComponentException("MutableDangerousField.getBlock: " + e.getMessage());
        }
    }

    /**
     * 清空可变非受保护区中，所有的子 Block
     */
    public void clearBlocks() {
        this.blocks.clear();
    }

    /**
     * 获取可变非受保护区所有的 Block
     *
     * @return
     */
    public ElementContainer getBlocks() {
        return this.blocks;
    }

    /**
     * 获取可变非受保护区中，第一个指定TLV-TYPE的子 TLV Block
     *
     * @return
     */
    public Block getBlockByType(VlInt tlvType) throws ComponentException {
        try {
            return this.blocks.getBlockByType(tlvType);
        } catch (BlockException e) {
            throw new ComponentException("MutableDangerousField.getBlockByType: " + e.getMessage());
        }
    }

    /**
     * 将可变非受保护区线速编码为一个 TLV
     *
     * @param encoder
     * @return
     */
    @Override
    public int wireEncode(Encoder encoder) throws ComponentException {
        try {
            // 如果可变非受保护区没有任何子 TLV，则可以去掉可变非受保护区 TLV
            if (this.blocks.length() == 0) {
                return 0;
            }

            int totalLength = 0;
            // 编码TLV-VALUE
            // 反向遍历，可以保证解码的时候正向输出
            for (int i = this.blocks.length() - 1; i >= 0; i--) {
                int tmplen = encoder.prependBlock(this.blocks.getBlock(i));
                if (tmplen < 0) {
                    return -1;
                }
                totalLength += tmplen;
            }

            // 编码 TLV-LENGTH
            int tmplen = encoder.prependVarNumber(new VlInt(totalLength));
            if (tmplen < 0) {
                return -1;
            }
            totalLength += tmplen;

            // 编码 TLV-TYPE
            tmplen = encoder.prependVarNumber(new VlInt(TLV.TlvMutableDangerousField));
            if (tmplen < 0) {
                return -1;
            }
            totalLength += tmplen;

            return totalLength;
        } catch (EncoderException | BlockException e) {
            throw new ComponentException("MutableDangerousField.wireEncode: " + e.getMessage());
        }
    }

    /**
     * 从 TLV Block 中解码出一个 ReadOnlyField
     *
     * @param block
     * @return
     */
    @Override
    public boolean wireDecode(Block block) throws ComponentException {
        // 检查 Type 是否正确
        if (!TLV.expectType(block.getType(), new VlInt(TLV.TlvMutableDangerousField))) {
            return false;
        }

        // 解析子 TLV
        try {
            if (!block.parseSubElements()) {
                return false;
            }
        } catch (BlockException e) {
            throw new ComponentException("MutableDangerousField.wireDecode: " + e.getMessage());
        }

        this.blocks = block.getSubElements();
        return true;
    }
}