package org.yzh.protocol.codec;
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import io.github.yezhihao.protostar.SchemaManager;
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import io.github.yezhihao.protostar.schema.RuntimeSchema;
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import io.github.yezhihao.protostar.util.ArrayMap;
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import io.github.yezhihao.protostar.util.Explain;
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import io.netty.buffer.*;
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import org.yzh.protocol.basics.JTMessage;
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import org.yzh.protocol.commons.Bit;
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import org.yzh.protocol.commons.JTUtils;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* JT协议解码器
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* @author yezhihao
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* https://gitee.com/yezhihao/jt808-server
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*/
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public class JTMessageDecoder {
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private static final ByteBufAllocator ALLOC = PooledByteBufAllocator.DEFAULT;
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private final SchemaManager schemaManager;
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private final ArrayMap<RuntimeSchema> headerSchemaMap;
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public JTMessageDecoder(String... basePackages) {
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this.schemaManager = new SchemaManager(basePackages);
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this.headerSchemaMap = schemaManager.getRuntimeSchema(JTMessage.class);
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}
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public JTMessageDecoder(SchemaManager schemaManager) {
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this.schemaManager = schemaManager;
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this.headerSchemaMap = schemaManager.getRuntimeSchema(JTMessage.class);
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}
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public JTMessage decode(ByteBuf input) {
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return decode(input, null);
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}
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public JTMessage decode(ByteBuf input, Explain explain) {
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ByteBuf buf = unescape(input);
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boolean verified = verify(buf);
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int messageId = buf.getUnsignedShort(0);
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int properties = buf.getUnsignedShort(2);
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int version = 0;//缺省值为2013版本
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if (Bit.isTrue(properties, 14))//识别2019及后续版本
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version = buf.getUnsignedByte(4);
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boolean isSubpackage = Bit.isTrue(properties, 13);
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int headLen = JTUtils.headerLength(version, isSubpackage);
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RuntimeSchema<JTMessage> headSchema = headerSchemaMap.get(version);
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RuntimeSchema<JTMessage> bodySchema = schemaManager.getRuntimeSchema(messageId, version);
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JTMessage message;
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if (bodySchema == null)
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message = new JTMessage();
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else
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message = bodySchema.newInstance();
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message.setVerified(verified);
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message.setPayload(input);
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int writerIndex = buf.writerIndex();
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buf.writerIndex(headLen);
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headSchema.mergeFrom(buf, message, explain);
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buf.writerIndex(writerIndex - 1);
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int realVersion = message.getProtocolVersion();
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if (realVersion != version)
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bodySchema = schemaManager.getRuntimeSchema(messageId, realVersion);
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if (bodySchema != null) {
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int bodyLen = message.getBodyLength();
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if (isSubpackage) {
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ByteBuf bytes = ALLOC.buffer(bodyLen);
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buf.getBytes(headLen, bytes);
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ByteBuf[] packages = addAndGet(message, bytes);
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if (packages == null)
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return message;
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ByteBuf bodyBuf = Unpooled.wrappedBuffer(packages);
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bodySchema.mergeFrom(bodyBuf, message, explain);
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if (message.noBuffer()) {
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bodyBuf.release();
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}
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} else {
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buf.readerIndex(headLen);
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bodySchema.mergeFrom(buf, message, explain);
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}
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}
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return message;
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}
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protected ByteBuf[] addAndGet(JTMessage message, ByteBuf bytes) {
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return null;
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}
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/** 校验 */
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public static boolean verify(ByteBuf buf) {
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byte checkCode = JTUtils.bcc(buf, -1);
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return checkCode == buf.getByte(buf.writerIndex() - 1);
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}
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/** 反转义 */
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public static ByteBuf unescape(ByteBuf source) {
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int low = source.readerIndex();
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int high = source.writerIndex();
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if (source.getByte(low) == 0x7e)
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low++;
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if (source.getByte(high - 1) == 0x7e)
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high--;
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int mark = source.indexOf(low, high - 1, (byte) 0x7d);
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if (mark == -1) {
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return source.slice(low, high - low);
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}
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List<ByteBuf> bufList = new ArrayList<>(3);
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int len;
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do {
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len = mark + 2 - low;
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bufList.add(slice(source, low, len));
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low += len;
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mark = source.indexOf(low, high, (byte) 0x7d);
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} while (mark > 0);
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bufList.add(source.slice(low, high - low));
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return new CompositeByteBuf(ALLOC, false, bufList.size(), bufList);
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}
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/** 截取转义前报文，并还原转义位 */
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protected static ByteBuf slice(ByteBuf byteBuf, int index, int length) {
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byte second = byteBuf.getByte(index + length - 1);
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if (second == 0x01) {
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return byteBuf.slice(index, length - 1);
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} else if (second == 0x02) {
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byteBuf.setByte(index + length - 2, 0x7e);
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return byteBuf.slice(index, length - 1);
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} else {
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return byteBuf.slice(index, length);
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}
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}
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}
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