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package net.sf.jrtps.message.parameter;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

import net.sf.jrtps.transport.RTPSByteBuffer;

/**
 * see 8.7.9 Key Hash, 9.6.3.3
 * 
 * @author mcr70
 * 
 */
public class KeyHash extends Parameter implements InlineQoS {

    private static MessageDigest md5 = null;
    private static NoSuchAlgorithmException noSuchAlgorithm = null;
    static {
        try {
            md5 = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            noSuchAlgorithm = e; // Actual usage might not even need it.
        }
    }    

    private byte[] bytes;
    

    KeyHash() {
        super(ParameterId.PID_KEY_HASH);
    }
    
    public KeyHash(byte[] bytes) {
        super(ParameterId.PID_KEY_HASH);
        this.bytes = prepareKey(bytes);
    }

    @Override
    public byte[] getBytes() {
        return bytes;
    }
    
    /**
     * Get the key hash. Key hash is always of length 16;
     * 
     * @return Key hash as byte array
     */
    public byte[] getKeyHash() {
        return bytes;
    }

    @Override
    public void read(RTPSByteBuffer bb, int length) {
        this.bytes = new byte[16];
        bb.read(bytes);
    }

    @Override
    public void writeTo(RTPSByteBuffer bb) {
        bb.write(bytes);
    }
    
    public boolean equals(Object other) {
        if (other instanceof KeyHash) {
            return Arrays.equals(getKeyHash(), ((KeyHash)other).getKeyHash());
        }
        
        return false;
    }
    
    public int hashCode() {
        return Arrays.hashCode(getKeyHash());
    }
    
    
    public String toString() {
        return "KeyHash" + Arrays.toString(bytes);
    }

    private byte[] prepareKey(byte[] key) {        
        if (key == null) {
            key = new byte[0];
        }
        
        byte[] bytes = null;
        if (key.length <= 16) {
            bytes = new byte[16];
            System.arraycopy(key, 0, bytes, 0, key.length);
        } else {
            if (md5 == null) {
                throw new RuntimeException(noSuchAlgorithm);
            }

            synchronized (md5) {
                bytes = md5.digest(key);
                md5.reset();                
            }
        }

        return bytes;
    }
}