我有一个通过 rs232 与程序通信的设备。设备发送一条消息，程序逐字节读取并放入缓冲区，以便另一个线程解析缓冲区。 问题是，在消息中我将有一个 0x00 字节 {fifo 缓冲区的空元素}，因此我无法在 fifo 中输入该元素。如何解决该问题。 我用的是
BlockingQueue<Byte> queue = new ArrayBlockingQueue<>(1000);
用于在 fifo 中输入字节:
public void serialEvent(jssc.SerialPortEvent event) {
if (event.isRXCHAR()) {//If data is available
try {
buffer = serialPort.readBytes();
System.out.println(bytesToHex(buffer) + " event");
for (int i = 0; i < buffer.length; i++) {
queue.add(buffer[i]);
}
} catch (SerialPortException ex) {
System.out.println(ex);
}
并轮询元素
byte stx = queue.poll();
如何输入空元素，因为消息将有空字节？
解析代码(解析线程):
public void run() {
while (true) {
while (!queue.isEmpty()) {
System.out.println(queue.size() + " 1 proverka");
sb = new StringBuilder();
byte stx = queue.poll();
System.out.println(byteToHex(stx) + " parser");
if (stx == 0x02) {
sb.append(String.format("%02X ", stx));
System.out.println(queue.size() + " 2 proverka");
for (int i = 0; i < 3; i++) {
System.out.println(queue.size() + " 3 proverka " + i + " krug");
len[i] = queue.poll();
System.out.println(byteToHex(len[i]) + " parser");
输出:
02 Activity 0000 事件 01 Activity 4 1 普罗维卡 77 事件 2个解析器 03 Activity 75 事件 6 2 普罗维卡 6 3 普罗韦尔卡 0 克鲁格 线程“Thread-1”中的异常 java.lang.NullPointerException 在 es.moduli.ingenico_card_reader.Ingenico_Card_Reader$SerialParser.run(Ingenico_Card_Reader.java:127)
使用我的自定义字节类进行编辑
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package es.moduli.ingenico_card_reader;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
import jssc.SerialPort;
import jssc.SerialPortEventListener;
import jssc.SerialPortException;
/**
*
* @author GiGo
*/
public class Ingenico_Card_Reader {
static SerialPort serialPort;
static BlockingQueue<CustomByte> queue = new ArrayBlockingQueue<>(1000);
final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
public void open() {
serialPort = new SerialPort("COM4");
try {
serialPort.openPort();//Open port
serialPort.setParams(9600, 8, 1, 0);//Set params
int mask = SerialPort.MASK_RXCHAR;//Prepare mask
serialPort.setEventsMask(mask);//Set mask
serialPort.addEventListener(new SerialPortEvent());//Add SerialPortEventListener
} catch (SerialPortException ex) {
System.out.println(ex);
}
SerialParser parser = new SerialParser();
parser.start();
}
public static String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for (int j = 0; j < bytes.length; j++) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
public static String byteToHex(byte b) {
int i = b & 0xFF;
return Integer.toHexString(i);
}
public static int byteToIntBE(byte[] b) {
ByteBuffer bb = ByteBuffer.wrap(b);
bb.order(ByteOrder.BIG_ENDIAN);
int result = bb.getInt();
return result;
}
public static void sleep(long i) {
try {
Thread.sleep(i);
} catch (Exception e) {
}
}
public static String hexString(byte[] b) {
StringBuilder d = new StringBuilder(b.length * 2);
for (int i = 0; i < b.length; i++) {
char hi = Character.forDigit(b[i] >> 4 & 0xF, 16);
char lo = Character.forDigit(b[i] & 0xF, 16);
d.append(Character.toUpperCase(hi));
d.append(Character.toUpperCase(lo));
}
return d.toString();
}
public static class SerialPortEvent implements SerialPortEventListener {
byte buffer[];
@Override
public void serialEvent(jssc.SerialPortEvent event) {
if (event.isRXCHAR()) {//If data is available
//if (event.getEventValue() == 1) {//Check bytes count in the input buffer
//Read data, if 1 byte available
try {
buffer = serialPort.readBytes();
System.out.println(bytesToHex(buffer) + " event");
for (int i = 0; i < buffer.length; i++) {
queue.add(new CustomByte(buffer[i], true));
}
} catch (SerialPortException ex) {
System.out.println(ex);
}
}
// }
}
}
public static class SerialParser extends Thread {
StringBuilder sb = new StringBuilder();
Byte len[];
int len_mess = 0;
Byte mess[];
@Override
public void run() {
while (true) {
while (!queue.isEmpty()) {
System.out.println(queue.size() + " 1 proverka");
sb = new StringBuilder();
byte stx = queue.poll().getBufferByte();
System.out.println(byteToHex(stx) + " parser");
if (stx == 0x02) {
sb.append(String.format("%02X ", stx));
System.out.println(queue.size() + " 2 proverka");
for (int i = 0; i < 3; i++) {
System.out.println(queue.size() + " 3 proverka " + i + " krug");
len[i] = queue.poll().getBufferByte();
System.out.println(byteToHex(len[i]) + " parser");
//sb.append(String.format("%02X ", len[i]));
}
len_mess = (256 * 256 * len[0]) + (256 * len[1]) + (len[2]);
for (int i = 0; i < len_mess; i++) {
mess[i] = queue.poll().getBufferByte();
System.out.println(byteToHex(mess[i]) + "parser");
sb.append(String.format("%02X ", mess[i]));
try {
Thread.sleep(50);
} catch (InterruptedException ex) {
System.out.println(ex.getMessage());
}
}
byte etx = queue.poll().getBufferByte();
System.out.println(byteToHex(etx) + "parser");
if (etx == 0x03) {
sb.append(String.format("%02X ", etx));
System.out.println(sb.toString());
} else {
System.out.println("NOT ETX");
}
} else {
System.out.println("NOT STX");
}
System.out.println(sb.toString());
}
}
}
}
}
同样的错误
02 Activity 0000017703 事件 6 1 普罗韦尔卡 2个解析器 75 事件 6 2 普罗维卡 6 3 普罗韦尔卡 0 克鲁格 线程“Thread-1”中的异常 java.lang.NullPointerException 在 es.moduli.ingenico_card_reader.Ingenico_Card_Reader$SerialParser.run(Ingenico_Card_Reader.java:129)
最佳答案
一个BlockingQueue<Byte>可以有(byte) 0x00然而，这是处理字节流的非常低效的方法。这将为每个实际发送的字节创建大约 16 字节的垃圾。
另一种方法是使用专为此类任务设计的 Pipe 流。
PipedOutputStream out = new PipedOutputStream();
PipedInputStream in = new PipedInputStream(out);
在从RS232读取的线程中，可以将读取到的字节写入out在另一个线程中，您可以通过读取 in 来处理此问题.
此方法不会在每个字节的基础上产生任何垃圾。
关于java - 允许空元素的 Fifo 缓冲区，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/29252442/