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  1. /* package whatever; // don't place package name! */
  2.  
  3. /* The class name doesn't have to be Main, as long as the class is not public. */
  4. class Main
  5. {
  6.   private static int crc16(final byte[] buffer) {
  7.     int crc = 0xFFFF;
  8.  
  9.     for (int j = 0; j < buffer.length ; j++) {
  10.         crc = ((crc  >>> 8) | (crc  << 8) )& 0xffff;
  11.         crc ^= (buffer[j] & 0xff);//byte to int, trunc sign
  12.         crc ^= ((crc & 0xff) >> 4);
  13.         crc ^= (crc << 12) & 0xffff;
  14.         crc ^= ((crc & 0xFF) << 5) & 0xffff;
  15.     }
  16.     crc &= 0xffff;
  17.     return crc;
  18.  
  19.   }
  20.   // Compute the MODBUS RTU CRC
  21.   private static int ModRTU_CRC(byte[] buf, int len)
  22.   {
  23.     int crc = 0xFFFF;
  24.  
  25.     for (int pos = 0; pos < len; pos++) {
  26.       crc ^= (int)buf[pos];          // XOR byte into least sig. byte of crc
  27.  
  28.       for (int i = 8; i != 0; i--) {    // Loop over each bit
  29.         if ((crc & 0x0001) != 0) {      // If the LSB is set
  30.           crc >>= 1;                    // Shift right and XOR 0xA001
  31.           crc ^= 0xA001;
  32.         }
  33.         else                            // Else LSB is not set
  34.           crc >>= 1;                    // Just shift right
  35.       }
  36.     }
  37.     // Note, this number has low and high bytes swapped, so use it accordingly (or swap bytes)
  38.     return crc;  
  39.   }
  40.   public static void main (String[] args) throws java.lang.Exception
  41.   {
  42.      byte[] buf = new byte[] { (byte) 0x01, (byte) 0x04, (byte)0x00, (byte)0x01,(byte)0x00, (byte) 0x01};
  43.      int crc = ModRTU_CRC(buf, 6);
  44.      //java.io.BufferedReader r = new java.io.BufferedReader (new java.io.InputStreamReader (System.in));
  45.      System.out.println(crc);
  46.      crc = crc16(buf);
  47.      System.out.println(crc);
  48.  
  49.      //while (!(s=r.readLine()).startsWith("42")) System.out.print(crc);
  50.   }
  51. }
  52.  
  53.  
Success #stdin #stdout 0.07s 381248KB
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stdin
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1
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42
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stdout
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2656
58791
https://ideone.com/PrBXVh
language:
Java (HotSpot 12)
created:
11 years ago
visibility:
secret

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