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/*-
 * Copyright (C) 2011, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This file was distributed by Oracle as part of a version of Oracle NoSQL
 * Database made available at:
 *
 * http://www.oracle.com/technetwork/database/database-technologies/nosqldb/downloads/index.html
 *
 * Please see the LICENSE file included in the top-level directory of the
 * appropriate version of Oracle NoSQL Database for a copy of the license and
 * additional information.
 */

package oracle.kv;

import static oracle.kv.impl.util.ObjectUtil.checkNull;
import static oracle.kv.impl.util.SerializationUtil.readNonNullSequenceLength;
import static oracle.kv.impl.util.SerializationUtil.readNonNullString;
import static oracle.kv.impl.util.SerializationUtil.writeNonNullSequenceLength;
import static oracle.kv.impl.util.SerializationUtil.writeNonNullString;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.Arrays;

import oracle.kv.impl.util.FastExternalizable;
import oracle.kv.impl.util.SerializationUtil;

/**
 * Username/password credentials.  This class provides the standard mechanism
 * for an application to authenticate as a particular user when accessing a
 * KVStore instance.  The object contains sensitive information and should be
 * kept private.  When no longer needed the user should call clear() to erase
 * the internal password information.
 *
 * @hiddensee {@link #writeFastExternal FastExternalizable format}
 * @since 3.0
 */
public class PasswordCredentials
        implements FastExternalizable, LoginCredentials, Serializable {
    private static final long serialVersionUID = 1L;
    private String username;
    private char[] password;

    /**
     * Creates a username/password credential set.   The password passed in is
     * copied internal to the object.  For maximum security, it is recommended
     * that you call the {@link #clear()} method when you are done with the
     * object to avoid have the password being present in the Java memory heap.
     *
     * @param username the name of the user
     * @param password the password of the user
     * @throws IllegalArgumentException if either username or password
     * have null values.
     */
    public PasswordCredentials(String username, char[] password)
        throws IllegalArgumentException {

        if (username == null) {
            throw new IllegalArgumentException(
                "The username argument must not be null");
        }
        if (password == null) {
            throw new IllegalArgumentException(
                "The password argument must not be null");
        }
        this.username = username;
        this.password = Arrays.copyOf(password, password.length);
    }

    /**
     * Creates an instance from the input stream.
     *
     * @hidden For internal use only
     */
    public PasswordCredentials(DataInput in, short serialVersion)
        throws IOException {

        username = readNonNullString(in, serialVersion);
        password = new char[readNonNullSequenceLength(in)];
        for (int i = 0; i < password.length; i++) {
            password[i] = in.readChar();
        }
    }

    /**
     * Writes the fields of this object to the output stream.  Format:
     * 
     *  ({@link SerializationUtil#writeNonNullString non-null String})
     *      {@link #getUsername username}
     * 
 ({@link SerializationUtil#writeNonNullSequenceLength non-null
     *      sequence length}) password length
     * 
 For each character in {@link #getPassword password}:
     *    
     *     ({@link DataOutput#writeChar char}) password char
     *    
     * 
     *
     * @hidden For internal use only
     */
    @Override
    public void writeFastExternal(DataOutput out, short serialVersion)
        throws IOException {

        writeNonNullString(out, serialVersion, username);
        writeNonNullSequenceLength(out, password.length);
        for (final char c : password) {
            out.writeChar(c);
        }
    }

    /**
     * @see LoginCredentials#getUsername()
     */
    @Override
    public String getUsername() {
        return username;
    }

    /**
     * Gets the password. This returns a copy of the password. The caller should
     * clear the returned memory when the value is no longer needed.
     *
     * @return The password for the user.
     */
    public char[] getPassword() {
        return Arrays.copyOf(password, password.length);
    }

    /**
     * Wipes out the password storage to ensure it does not hang around in the
     * Java VM memory space.
     */
    public void clear() {
        Arrays.fill(password, ' ');
    }

    /** Check for valid fields. */
    private void readObject(ObjectInputStream in)
        throws ClassNotFoundException, IOException {

        in.defaultReadObject();
        try {
            checkNull("username", username);
            checkNull("password", password);
        } catch (IllegalArgumentException e) {
            throw new IOException("Invalid field: " + e.getMessage(), e);
        }
    }
}