如何將一個字節數組複製到另一個字節數組中？

Question

我正在研究一個簡單的應用程序來演示P2P文件傳輸。應用程序獲取文件，並通過數據包大小的數據塊發送。接收器等待這些塊到達。它假設不斷地將傳入的字節數組添加到一個更大的字節數組中，一旦所有字節都到達，該數組稍後將成爲完成的文件。這假設沒有丟包。爲了調試我一直在試圖傳輸一個小的txt文件。我嘗試使用for循環，現在System.arraycopy但packetData的字節數組似乎沒有正確複製到completeFile數組。

public void run() { 
    try { 
     byte[] completeFile = new byte[fileSize];//will become the complete file when all bytes have arrived 

     receivingSocket = new DatagramSocket(49000); 
     while (bytesReceived<fileSize) { 
      System.out.println("@@@ Receiver waiting for packet"); 
      byte[] buf = new byte[1500]; // Actual Ethernet packet size is 1500 bytes 
      // receive request 
      DatagramPacket packet = new DatagramPacket(buf, buf.length); 
      receivingSocket.receive(packet); 
      byte[] packetData = Arrays.copyOf(packet.getData(), packet.getLength()); 
      deliverData(packetData); 
      if(headerReceived && packetsReceived>1) 
      { 
       //add incoming bytes to the completeFile 
       System.arraycopy(packetData, 0, completeFile, bytesReceived, packetData.length); 
       bytesReceived = bytesReceived + packetData.length; 
      } 
     } 
     FileOutputStream fops = new FileOutputStream("D:\\Desktop\\testing2"+fileExtension); 
     System.out.println("@@@ BUILDING FILE"); 
     fops.write(completeFile); 
     fops.close(); 
    } catch (Exception e) { 
     System.out.println("@@@ SOMETHING WENT WRONG!!!!!!!!!!!!!!"); 
     stopListening(); 
    } 
} 

Answer 1

你不需要複製任何東西。您可以直接從用於構建DatagramPacket,的字節數組直接寫入文件，並且可以將該字節數組直接傳遞給其他方法，以及來自數據包的長度。