/*
* Copyright (c) 2008 Nokia Corporation and/or its subsidiary(-ies).
* All rights reserved.
* This component and the accompanying materials are made available
* under the terms of "Eclipse Public License v1.0"
* which accompanies this distribution, and is available
* at the URL "http://www.eclipse.org/legal/epl-v10.html".
*
* Initial Contributors:
* Nokia Corporation - initial contribution.
*
* Contributors:
*
* Description:
*
*/

package javax.microedition.io;

import java.security.Permission;
import java.security.PermissionCollection;

/**
 * This class represents access rights to connections via the "datagram"
 * protocol. A DatagramProtocolPermission consists of a URI string but
 * no actions list.
 * <p>
 * The URI string specifies a connection for sending and receiving datagrams.
 * It takes the following general form:
 * <p>
 * datagram://{host}:{portspec} | datagram://[:{portspec}]
 * <p>
 * The exact syntax for the DatagramProtocolPermission URI is provided by this
 * BNF. The value of the {host} field must be a symbolic hostname, a literal
 * IPv4 address or a literal IPv6 address, as specified by RFC 3986. The {host}
 * field is omitted to indicate an inbound, "server mode" connection.
 * Server-mode URIs may also omit the {portspec} field to request a
 * system-assigned port number. In such a case, the DatagramProtocolPermission
 * is normalized to the equivalent URI "datagram://:1024-65535".
 * <p>
 * If the {host} string is a DNS name, an asterisk may appear in the leftmost
 * position to indicate a match of 1 or more entire domain labels. Partial
 * domain label matches are not permitted, therefore "*.sun.com" is valid,
 * but "*sun.com" is not. An asterisk by itself matches all hosts in outbound,
 * "client-mode" connections.
 * <p>
 * The {portspec} string takes the following form:
 * <p>
 * portnumber | -portnumber | portnumber-[portnumber] | "*"
 * <p>
 * A {portspec} specification of the form "N-" (where N is a port number)
 * signifies all ports numbered N and above, while a specification of the form
 * "-N" indicates all ports numbered N and below. A single asterisk in the
 * place of the {portspec} field matches all ports. Therefore, the URI
 * "datagram://:*" matches server-mode datagram connections to all ports,
 * and the URI "datagram://*:*" matches client-mode datagram connections to
 * all hosts on all ports.
 *
 * @see DatagramConnection
 * @see Connector.open(java.lang.String)
 * @see "javax.microedition.io.UDPDatagramConnection" in MIDP 3.0 Specification
 *
 * @author Nokia Corporation
 * @version 1.0
 */
public final class DatagramProtocolPermission
        extends GCFPermission
{
    /**
     * Creates a new DatagramProtocolPermission with the specified URI as
     * its name. The URI string must conform to the specification given
     * above, and is normalized  to facilitate subsequent comparisons.
     *
     * @param uri the URI string
     * @throws IllegalArgumentException - if uri is malformed.
     * @throws NullPointerException - if uri is null.
     */
    public DatagramProtocolPermission(String uri)
    {
        super(uri);
    }

    /**
     * Checks if this DatagramProtocolPermission object "implies" the
     * specified permission.
     * <p>
     * Because the {host} field of the permission URI may indicate an
     * individual host by means of either a symbolic hostname or an IP
     * address, a thorough evaluation of the implies relation between
     * two DatagramProtocolPermission objects requires the underlying
     * platform to be able to transform symbolic hostnames into IP addresses
     * (via address lookup) and vice-versa (via name lookup). Either service
     * may be unavailable on a given platform. As a result, the comparison
     * of URI strings from two permissions can only be best-effort. For each
     * DatagramProtocolPermission constructed with a URI that contains a
     * {host} field, the implementation will attempt to determine both the
     * fully-qualified domain name (the "canonical name") and the IP
     * address(es) of the host. However, either value may be unknown.
     * <p>
     * To determine whether this object implies another permission, p, this
     * method first ensures that all of the following are true
     * (and returns false if any of them are not):
     * <ul>
     * <li>p is an instanceof DatagramProtocolPermission, and</li>
     * <li>p's port range is included in this port range.</li>
     * </ul>
     * Then implies checks each of the following, in order, and for each
     * returns true if the stated condition is true:
     * <ul>
     * <li>If both this object and p lack the {host}  field.</li>
     * <li>If this object has a single IP address and one of p's IP
     * addresses is equal to this object's IP address.</li>
     * <li>If this object has a wildcard domain (such as *.sun.com),
     * and p's absolute name (the name with any preceding * removed) ends
     * with this object's aboslute name. For example,
     * *.sun.com implies *.eng.sun.com.</li>
     * <li>If this object has multiple IP addresses, and one of this object's
     * IP addresses equals one of p's IP addresses.</li>
     * <li>If this object's canonical name equals p's canonical name.</li>
     * </ul>
     * If none of the above are true, implies returns false.
     *
     * @param p the permission to check against.
     * @return true if the specified permission is implied by this object,
     *        false if not.
     */
    public boolean implies(Permission p)
    {
        if (p instanceof DatagramProtocolPermission)
        {
            return true;
        }
        return false;
    }

    /**
     * Checks two DatagramProtocolPermission objects for equality.
     *
     * @param obj the object we are testing for equality with this object.
     * @return true if obj is a DatagramProtocolPermission and has the
     *         same URI string as this DatagramProtocolPermission object.
     */
    public boolean equals(Object obj)
    {
        return true;
    }

    /**
     * Returns the hash code value for this object.
     *
     * @return a hash code value for this object.
     */
    public int hashCode()
    {
        return 0;
    }

    /**
     * Returns the canonical string representation of the actions,
     * which currently is the empty string "", since there are no
     * actions defined for DatagramProtocolPermission.
     *
     * @return the empty string "".
     */
    public String getActions()
    {
        return "";
    }

    /**
     * Returns a new PermissionCollection for storing
     * DatagramProtocolPermission objects.
     * <p>
     * DatagramProtocolPermission objects must be stored in a manner that
     * allows them to be inserted into the collection in any order, but
     * that also enables the PermissionCollection implies method to be
     * implemented in an efficient (and consistent) manner.
     *
     * @return a new PermissionCollection object suitable for storing
     *         DatagramProtocolPermission objects.
     */
    public PermissionCollection newPermissionCollection()
    {
        return null;
    }
}