从 .txt 中一次获取 16 个字节

Question

我有两个文件，一个发送，一个接收。我知道两者之间的联系。

可以发送文本：

// Prepare a message 
 messageToSend = "text that is sent";
 lengthMessageToSend = messageToSend.length(); 
 sendingBuffer = messageToSend.getBytes();


// Send the message
 myLink.sendFrame(sendingBuffer, lengthMessageToSend);
 System.out.println(lengthMessageToSend);

并接收：

// Display the message
  messageReceived = new String(receivingBuffer, 0, lengthMessageReceived);
  System.out.println("Message received is: [" + messageReceived + "]"); 

// Prepare a message  
  messageToSend = "1";
  lengthMessageToSend = messageToSend.length(); 
  sendingBuffer = messageToSend.getBytes();

 // Send the message
  myLink.sendFrame(sendingBuffer, lengthMessageToSend);

我现在尝试发送的文本来自 .txt，但只是在有效载荷内一次发送 16 个字节：

[序列 |伦 |有效载荷 | CHECKSUM ] --> 总共 Header 19 个字节。

最好的方法是什么？

一次只读取 16 个字节（8 个字符）？？如果是怎么办？

Answer 1

循环并每次将i递增16，这个i表示messageToSend.getBytes()偏移量的开始-然后将接下来的16个字节（从i到i+16，处理剩余少于 16 个字节的情况) 放入 'packet' 并发送。

也使用 getBytes() 的显式编码，否则环境设置可能会导致 'unexpected behavioral changes'。

这样的基本实现可能类似于：

byte[] data = messageToSend.getBytes("UTF-8"); // Specify encoding!

// "For all data, stepping by 16 bytes at a time.."
for (int i = 0; i < data.length; i += 16) {
   // How many bytes actually remain (or 16 if more than 16 remain)
   var frameSize = Math.min(16, data.length - i);

   // Construct frame data from data in i..i+frameSize and send.
   // If you want to ALWAYS send 16 bytes, update as appropriate.
   byte[] frameData = new byte[frameSize];
   System.arraycopy(data, i, frameData, 0, frameSize);

   sendFrame(frameData, frameSize);
}

必须修改代码以添加序列号，但这应该不难，因为它总是递增一个。

读取过程类似：根据 length/framing 数据消耗数据包头并处理剩余缓冲区（可能包括下一个数据包的开头）。

// Assuming new frames are always copied-to-start and that there
// if a complete frame ready (can be determined from frame size with)
// two reads. If not, keep reading..
byte[] receivingBuffer = ..;
int offset = 0;
int seq = receivingBuffer[offset++];
int frameSize = receivingBuffer[offset++];

// Again, use an encoding
String content = new String(receivingBuffer, offset, frameSize, "UTF-8");
offset += frameSize;

int checksum = receivingBuffer[offset++];

// Use offset to move extra data in receivingBuffer to start
// of buffer to make it easy to reset offset to 0 and repeat above.

从 .txt 中一次获取 16 个字节

Getting 16 bytes at a time from .txt

java

string

byte

network-programming