/*
 * Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.security.acls.model;

import java.io.Serializable;

/**
 * Represents a permission granted to a <tt>Sid</tt> for a given domain object.
 *
 * @author Ben Alex
 */
public interface Permission extends Serializable {
	// ~ Static fields/initializers
	// =====================================================================================

	char RESERVED_ON = '~';
	char RESERVED_OFF = '.';
	String THIRTY_TWO_RESERVED_OFF = "................................";

	// ~ Methods
	// ========================================================================================================

	/**
	 * Returns the bits that represents the permission.
	 *
	 * @return the bits that represent the permission
	 */
	int getMask();

	/**
	 * Returns a 32-character long bit pattern <code>String</code> representing this
	 * permission.
	 * <p>
	 * Implementations are free to format the pattern as they see fit, although under no
	 * circumstances may {@link #RESERVED_OFF} or {@link #RESERVED_ON} be used within the
	 * pattern. An exemption is in the case of {@link #RESERVED_OFF} which is used to
	 * denote a bit that is off (clear). Implementations may also elect to use
	 * {@link #RESERVED_ON} internally for computation purposes, although this method may
	 * not return any <code>String</code> containing {@link #RESERVED_ON}.
	 * <p>
	 * The returned String must be 32 characters in length.
	 * <p>
	 * This method is only used for user interface and logging purposes. It is not used in
	 * any permission calculations. Therefore, duplication of characters within the output
	 * is permitted.
	 *
	 * @return a 32-character bit pattern
	 */
	String getPattern();
}
