CRC16.java

package com.eveningoutpost.dexdrip.ImportedLibraries.dexcom;

// This code and this particular library are from the NightScout android uploader
// Check them out here: https://github.com/nightscout/android-uploader
// Some of this code may have been modified for use in this project

public class CRC16 {
    public static byte[] calculate(byte[] buff, int start, int end) {
        int crcShort = 0;
        for (int i = start; i < end; i++) {
            crcShort = ((crcShort  >>> 8) | (crcShort  << 8) )& 0xffff;
            crcShort ^= (buff[i] & 0xff);
            crcShort ^= ((crcShort & 0xff) >> 4);
            crcShort ^= (crcShort << 12) & 0xffff;
            crcShort ^= ((crcShort & 0xFF) << 5) & 0xffff;
        }
        crcShort &= 0xffff;
        return new byte[] {(byte) (crcShort & 0xff), (byte) ((crcShort >> 8) & 0xff)};
    }
}