From 212931ff2bb2c2060e9a873aa8392d9ccae4f7fd Mon Sep 17 00:00:00 2001
From: free will <2647778488@qq.com>
Date: Fri, 17 Dec 2021 15:27:38 +0800
Subject: [PATCH] =?UTF-8?q?=E5=9C=A8VMSConnection=E6=A8=A1=E5=9D=97?=
 =?UTF-8?q?=E4=B8=AD=E7=9A=84BC=5FEncoder=E7=B1=BB=E4=B8=AD=E5=8A=A0?=
 =?UTF-8?q?=E5=85=A5=E9=AD=94=E6=95=B0=EF=BC=8C=E5=87=8F=E5=B0=91=E6=9C=8D?=
 =?UTF-8?q?=E5=8A=A1=E5=99=A8=E7=AB=AF=E7=9A=84=E5=86=85=E5=AD=98error?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../VMSConnection/Encoding/BC_Encoder.java    | 37 ++++++++++++++++---
 1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/src/main/java/VMSConnection/Encoding/BC_Encoder.java b/src/main/java/VMSConnection/Encoding/BC_Encoder.java
index 7ec52aa..a528be2 100644
--- a/src/main/java/VMSConnection/Encoding/BC_Encoder.java
+++ b/src/main/java/VMSConnection/Encoding/BC_Encoder.java
@@ -13,16 +13,23 @@ import java.nio.channels.SocketChannel;
  * @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 BC_Encoder {
+    // 魔数：为了避免读取数据时，因为读错开始的数据长度，而导致后台分配一块巨大的内存，出现内存错误
+    final static int magicNumber = 1803118696; // 后台设定的数字为uint32：0x6b796868
+    // 转为byte[]的魔数。小端字节序，4个字节
+    final static byte[] magicNumberBytes = ByteHelper.int32ToByteArray(magicNumber);
+
     /**
      * Encode 将消息编码: 加一个长度头
+     * | 魔数 | length | data |
      * @param message
      * @return
      */
     public static byte[] Encode(byte[] message){
         byte[] length= ByteHelper.int32ToByteArray(message.length);
-        byte[] pkg=new byte[4+ message.length];
-        System.arraycopy(length,0,pkg,0,4);
-        System.arraycopy(message,0,pkg,4,message.length);
+        byte[] pkg=new byte[4+4+ message.length];
+        System.arraycopy(magicNumberBytes,0,pkg,0,4);
+        System.arraycopy(length,0,pkg,4,4);
+        System.arraycopy(message,0,pkg,8,message.length);
         return pkg;
     }
 
@@ -43,6 +50,26 @@ public class BC_Encoder {
             }
         }
         System.out.println("start read...");
+        // 魔数
+        byte[] magicBuf=new byte[4];
+        try {
+            int revL=channel.socket().getInputStream().read(magicBuf);
+//            channel.read(ByteBuffer.wrap(buf));
+            if(revL<0){
+                System.out.println("magic read len < 0");
+                return null;
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+            return null;
+        }
+        int magicServerNumber=ByteHelper.byteArrayToInt32(magicBuf);
+        System.out.println("read magic number form server: "+magicServerNumber);
+        if(magicServerNumber!=magicNumber){
+            System.out.println("the magic number error: "+magicServerNumber
+                +", it should be "+magicNumber);
+            return null;
+        }
         // 读取消息的长度
         byte[] buf=new byte[4];
         try {
@@ -57,7 +84,7 @@ public class BC_Encoder {
             return null;
         }
         int length=ByteHelper.byteArrayToInt32(buf);
-        System.out.println("read 111: "+length);
+        System.out.println("read 111-length: "+length);
         // 读取真正的消息数据
         byte[] pkg=new byte[length]; // 最终读取的数据区
         byte[] cachepkg=new byte[length]; // 缓存数据区
@@ -84,7 +111,7 @@ public class BC_Encoder {
                 return null;
             }
         }
-        System.out.println("read 222: "+new String(pkg));
+        System.out.println("read 222-pkg: "+new String(pkg));
         return pkg;
     }
 }