MRN to UUID

gistfile1.txt

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.util.UUID;

public class MRNToUUID {
    public static UUID createUUIDFromMRN(String mrn) throws Exception {
        // Normalize the MRN
        String normMRN = mrn.toLowerCase();

        // Hash the MRN using SHA-256
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        byte[] hash = digest.digest(normMRN.getBytes(StandardCharsets.UTF_8));

        // A UUIDv8 accordingly to RFC 9562:

        // Most significant bits: custom_a (48 bits) + version (4 bits) + custom_b (12 bits)
        long mostSigBits = ((hash[0] & 0xFFL) << 40) | ((hash[1] & 0xFFL) << 32) |
                           ((hash[2] & 0xFFL) << 24) | ((hash[3] & 0xFFL) << 16) |
                           ((hash[4] & 0xFFL) << 8) | (hash[5] & 0xFFL);
        mostSigBits = (mostSigBits << 4) | 0x8; // Add version (4 bits: 0b1000 for UUIDv8)
        mostSigBits = (mostSigBits << 12) | ((hash[6] & 0xFFL) << 4) | ((hash[7] >> 4) & 0xF); // Add custom_b (12 bits)

        // Least significant bits: variant (2 bits) + custom_c (62 bits)
        long leastSigBits = ((hash[7] & 0x0FL) << 60) | ((hash[8] & 0xFFL) << 52) |
                            ((hash[9] & 0xFFL) << 44) | ((hash[10] & 0xFFL) << 36) |
                            ((hash[11] & 0xFFL) << 28) | ((hash[12] & 0xFFL) << 20) |
                            ((hash[13] & 0xFFL) << 12) | ((hash[14] & 0xFFL) << 4) | ((hash[15] >> 4) & 0xF);
        leastSigBits &= 0x3FFFFFFFFFFFFFFFL; // Clear variant bits
        leastSigBits |= 0x8000000000000000L; // Set variant to 0b10


        return new UUID(mostSigBits, leastSigBits);
    }

    public static void main(String[] args) throws Exception {
        String mrn = "urn:mrn:dk:atons:some-dataset";
        UUID uuid = createUUIDFromMRN(mrn);
        System.out.println("MRN: " + mrn);
        System.out.println("UUID: " + uuid.toString());
    }
}