java - 需要帮助纠正用 java 编写的 CRC-ITU 检查方法中的问题

Question

我们正在尝试用 Java 编写 GPS 设备监听器。

这样做时，我们无法为 CRC-ITU 错误检查开发正确的代码。从协议(protocol)文档生成crc码的解释如下

A check code may be used by the terminal or the server to distinguish whether the received information is in error or not. To prevent errors occurring during data transmission, error check is added to against data misoperation, so as to increase the security and efficiency of the system. The check code is generated by the CRC-ITU checking method. The check codes of data in the structure of the protocol, from the Packet Length to the Information Serial Number (including “Packet Length” and “Information Serial Number”), are values of CRC-ITU. If a CRC error occurs when the received information is calculated, the receiver will ignore and discard the data packet.

这是数据监听类

      byte[] data = new byte[20];
   System.out.println("Waiting for client on port " + serverSocket.getLocalPort() + "...");
                    Socket server = serverSocket.accept();
                    System.out.println("Just connected to " + server.getRemoteSocketAddress());
                    DataInputStream in = new DataInputStream(server.getInputStream());
                    System.out.println("in = " + in);
                    int packetSize = in.read(data, 0, data.length);
                    StringBuilder sb1 = new StringBuilder();
                    for (byte b : data) {
                        sb1.append(String.format("%02X ", b));
                    }
                    System.out.println("loginpacketHex = " + sb1.toString());
                    for (byte b : data) {
                        System.out.println("loginpacketinbytes = " + b);
                    }
                    NewClass cl = new NewClass();
                    byte[] t = new byte[4];
                    byte[] f = new byte[10];
                    t[0] = 0x05;
                    t[1] = data[3];
                    System.out.println(" t[1] = " + t[1]);
                    t[2] = data[data[2] - 6 + 5];
                    System.out.println("t[2] = " + t[2]);
                    t[3] = data[data[2] - 5 + 5];
                    System.out.println("t[3] = " + t[3]);
                    cl.set(t);
                    short x = cl.get();
                    f[0] = 0x78;
                    f[1] = 0x78;
                    f[2] = 0x05;
                    f[3] = data[3];
                    f[4] = data[data[2] - 6 + 5];
                    f[5] = data[data[2] - 5 + 5];
                    f[6] = (byte) ((x >> 8) & 0xff);
                    f[7] = (byte) (x & 0xff);
                    f[8] = 0x0d;
                    f[9] = 0x0a;

这是Crc生成类

public class NewClass {

    public static int crc;

    public static int[] table = {
        0x0000, 0x1189, 0x2312, 0x329B, 0x4624, 0x57AD, 0x6536, 0x74BF,
        0x8C48, 0x9DC1, 0xAF5A, 0xBED3, 0xCA6C, 0xDBE5, 0xE97E, 0xF8F7,
        0x1081, 0x0108, 0x3393, 0x221A, 0x56A5, 0x472C, 0x75B7, 0x643E,
        0x9CC9, 0x8D40, 0xBFDB, 0xAE52, 0xDAED, 0xCB64, 0xF9FF, 0xE876,
        0x2102, 0x308B, 0x0210, 0x1399, 0x6726, 0x76AF, 0x4434, 0x55BD,
        0xAD4A, 0xBCC3, 0x8E58, 0x9FD1, 0xEB6E, 0xFAE7, 0xC87C, 0xD9F5,
        0x3183, 0x200A, 0x1291, 0x0318, 0x77A7, 0x662E, 0x54B5, 0x453C,
        0xBDCB, 0xAC42, 0x9ED9, 0x8F50, 0xFBEF, 0xEA66, 0xD8FD, 0xC974,
        0x4204, 0x538D, 0x6116, 0x709F, 0x0420, 0x15A9, 0x2732, 0x36BB,
        0xCE4C, 0xDFC5, 0xED5E, 0xFCD7, 0x8868, 0x99E1, 0xAB7A, 0xBAF3,
        0x5285, 0x430C, 0x7197, 0x601E, 0x14A1, 0x0528, 0x37B3, 0x263A,
        0xDECD, 0xCF44, 0xFDDF, 0xEC56, 0x98E9, 0x8960, 0xBBFB, 0xAA72,
        0x6306, 0x728F, 0x4014, 0x519D, 0x2522, 0x34AB, 0x0630, 0x17B9,
        0xEF4E, 0xFEC7, 0xCC5C, 0xDDD5, 0xA96A, 0xB8E3, 0x8A78, 0x9BF1,
        0x7387, 0x620E, 0x5095, 0x411C, 0x35A3, 0x242A, 0x16B1, 0x0738,
        0xFFCF, 0xEE46, 0xDCDD, 0xCD54, 0xB9EB, 0xA862, 0x9AF9, 0x8B70,
        0x8408, 0x9581, 0xA71A, 0xB693, 0xC22C, 0xD3A5, 0xE13E, 0xF0B7,
        0x0840, 0x19C9, 0x2B52, 0x3ADB, 0x4E64, 0x5FED, 0x6D76, 0x7CFF,
        0x9489, 0x8500, 0xB79B, 0xA612, 0xD2AD, 0xC324, 0xF1BF, 0xE036,
        0x18C1, 0x0948, 0x3BD3, 0x2A5A, 0x5EE5, 0x4F6C, 0x7DF7, 0x6C7E,
        0xA50A, 0xB483, 0x8618, 0x9791, 0xE32E, 0xF2A7, 0xC03C, 0xD1B5,
        0x2942, 0x38CB, 0x0A50, 0x1BD9, 0x6F66, 0x7EEF, 0x4C74, 0x5DFD,
        0xB58B, 0xA402, 0x9699, 0x8710, 0xF3AF, 0xE226, 0xD0BD, 0xC134,
        0x39C3, 0x284A, 0x1AD1, 0x0B58, 0x7FE7, 0x6E6E, 0x5CF5, 0x4D7C,
        0xC60C, 0xD785, 0xE51E, 0xF497, 0x8028, 0x91A1, 0xA33A, 0xB2B3,
        0x4A44, 0x5BCD, 0x6956, 0x78DF, 0x0C60, 0x1DE9, 0x2F72, 0x3EFB,
        0xD68D, 0xC704, 0xF59F, 0xE416, 0x90A9, 0x8120, 0xB3BB, 0xA232,
        0x5AC5, 0x4B4C, 0x79D7, 0x685E, 0x1CE1, 0x0D68, 0x3FF3, 0x2E7A,
        0xE70E, 0xF687, 0xC41C, 0xD595, 0xA12A, 0xB0A3, 0x8238, 0x93B1,
        0x6B46, 0x7ACF, 0x4854, 0x59DD, 0x2D62, 0x3CEB, 0x0E70, 0x1FF9,
        0xF78F, 0xE606, 0xD49D, 0xC514, 0xB1AB, 0xA022, 0x92B9, 0x8330,
        0x7BC7, 0x6A4E, 0x58D5, 0x495C, 0x3DE3, 0x2C6A, 0x1EF1, 0x0F78,};

    public short get() {
        short c;
        int y;
        y = ~crc;
        c = (short) y;
        return c;
    }

    public void set(byte[] bytes) {
        crc = 0xffff;
        for (byte b : bytes) {
            crc = (crc >>> 8) ^ table[(crc ^ b) & 0xff];
        }
    }

}

Incoming data string comes in following format

    Example of data packet sent by the terminal 78 78 0D 01 01 23 45 67 89 01 23 45 00 01 8C DD 0D 0A

    Explanation

    Start Bit - 0x78 0x78
    Length - 0x0D
    Protocol - 0x01
    Terminal ID - 0x01 0x23 0x45 0x67 0x89 0x01 0x23 0x45
    Serial No - 0x00 0x01
    Error - 0x8C 0xDD
    Stop Bit - 0x0D 0x0A

我正在这样做更新代码。

ByteArrayOutputStream bytearrypacket = new ByteArrayOutputStream();
        DataOutputStream responce = new DataOutputStream(bytearrypacket);
        responce.writeByte(0x0D);
        responce.writeByte(1);
        responce.writeByte(0x03);
        responce.writeByte(0x53);
        responce.writeByte(0x49);
        responce.writeByte(0x20);
        responce.writeByte(0x49);
        responce.writeByte(0x00);
        responce.writeByte(0x05);
        responce.writeByte(0x34);
        responce.writeShort(2);
        NewClass cl = new NewClass();
        cl.set(bytearrypacket.toByteArray());
        System.out.println("cl = " + cl.get());
        System.out.println("hexhexhex = " + Integer.toHexString(cl.get()));
        responce.writeShort(cl.get());

        byte[] res = bytearrypacket.toByteArray();
        for (byte b : res) {
            System.out.println("b = " + b);
        }

Answer 1

这里是计算CRC的代码

公开课 CRCITUUtil {

private static int[] crcItuTable = {
    0X0000, 0X1189, 0X2312, 0X329B, 0X4624, 0X57AD, 0X6536, 0X74BF,
    0X8C48, 0X9DC1, 0XAF5A, 0XBED3, 0XCA6C, 0XDBE5, 0XE97E, 0XF8F7,
    0X1081, 0X0108, 0X3393, 0X221A, 0X56A5, 0X472C, 0X75B7, 0X643E,
    0X9CC9, 0X8D40, 0XBFDB, 0XAE52, 0XDAED, 0XCB64, 0XF9FF, 0XE876,
    0X2102, 0X308B, 0X0210, 0X1399, 0X6726, 0X76AF, 0X4434, 0X55BD,
    0XAD4A, 0XBCC3, 0X8E58, 0X9FD1, 0XEB6E, 0XFAE7, 0XC87C, 0XD9F5,
    0X3183, 0X200A, 0X1291, 0X0318, 0X77A7, 0X662E, 0X54B5, 0X453C,
    0XBDCB, 0XAC42, 0X9ED9, 0X8F50, 0XFBEF, 0XEA66, 0XD8FD, 0XC974,
    0X4204, 0X538D, 0X6116, 0X709F, 0X0420, 0X15A9, 0X2732, 0X36BB,
    0XCE4C, 0XDFC5, 0XED5E, 0XFCD7, 0X8868, 0X99E1, 0XAB7A, 0XBAF3,
    0X5285, 0X430C, 0X7197, 0X601E, 0X14A1, 0X0528, 0X37B3, 0X263A,
    0XDECD, 0XCF44, 0XFDDF, 0XEC56, 0X98E9, 0X8960, 0XBBFB, 0XAA72,
    0X6306, 0X728F, 0X4014, 0X519D, 0X2522, 0X34AB, 0X0630, 0X17B9,
    0XEF4E, 0XFEC7, 0XCC5C, 0XDDD5, 0XA96A, 0XB8E3, 0X8A78, 0X9BF1,
    0X7387, 0X620E, 0X5095, 0X411C, 0X35A3, 0X242A, 0X16B1, 0X0738,
    0XFFCF, 0XEE46, 0XDCDD, 0XCD54, 0XB9EB, 0XA862, 0X9AF9, 0X8B70,
    0X8408, 0X9581, 0XA71A, 0XB693, 0XC22C, 0XD3A5, 0XE13E, 0XF0B7,
    0X0840, 0X19C9, 0X2B52, 0X3ADB, 0X4E64, 0X5FED, 0X6D76, 0X7CFF,
    0X9489, 0X8500, 0XB79B, 0XA612, 0XD2AD, 0XC324, 0XF1BF, 0XE036,
    0X18C1, 0X0948, 0X3BD3, 0X2A5A, 0X5EE5, 0X4F6C, 0X7DF7, 0X6C7E,
    0XA50A, 0XB483, 0X8618, 0X9791, 0XE32E, 0XF2A7, 0XC03C, 0XD1B5,
    0X2942, 0X38CB, 0X0A50, 0X1BD9, 0X6F66, 0X7EEF, 0X4C74, 0X5DFD,
    0XB58B, 0XA402, 0X9699, 0X8710, 0XF3AF, 0XE226, 0XD0BD, 0XC134,
    0X39C3, 0X284A, 0X1AD1, 0X0B58, 0X7FE7, 0X6E6E, 0X5CF5, 0X4D7C,
    0XC60C, 0XD785, 0XE51E, 0XF497, 0X8028, 0X91A1, 0XA33A, 0XB2B3,
    0X4A44, 0X5BCD, 0X6956, 0X78DF, 0X0C60, 0X1DE9, 0X2F72, 0X3EFB,
    0XD68D, 0XC704, 0XF59F, 0XE416, 0X90A9, 0X8120, 0XB3BB, 0XA232,
    0X5AC5, 0X4B4C, 0X79D7, 0X685E, 0X1CE1, 0X0D68, 0X3FF3, 0X2E7A,
    0XE70E, 0XF687, 0XC41C, 0XD595, 0XA12A, 0XB0A3, 0X8238, 0X93B1,
    0X6B46, 0X7ACF, 0X4854, 0X59DD, 0X2D62, 0X3CEB, 0X0E70, 0X1FF9,
    0XF78F, 0XE606, 0XD49D, 0XC514, 0XB1AB, 0XA022, 0X92B9, 0X8330,
    0X7BC7, 0X6A4E, 0X58D5, 0X495C, 0X3DE3, 0X2C6A, 0X1EF1, 0X0F78,
};

public static byte[] getByteArrayFromInt(int value) {
    byte[] result = new byte[4];
    result[0] = (byte) (value >>> 24);
    result[1] = (byte) (value >>> 16);
    result[2] = (byte) (value >>> 8);
    result[3] = (byte) value;
    return result;
}

public static byte[] getCRCITU(byte[] data) {
    int crc = 0xffff;
    for (byte b : data) {
        crc = (crc >>> 8) ^ crcItuTable[(crc ^ b) & 0xff];
    }
    crc = ~crc;
    return getByteArrayFromInt(crc);
}
public static void main(String[] args) {
    byte[] bytes = CRCITUUtil
            .getCRCITU(new byte[] {0x0D, 0x01, 0x01, 0x23, 0x45, 0x67, (byte) 0x89, 0x01, 0x23, 0x45, 0x00, 0x01});
    System.out.println("CRCUIT:"+ Integer.toHexString(0xff & bytes[2]) + " " +  Integer.toHexString(0xff & bytes[3]));
}

这将打印

CRCUIT:8c dd