gcc/libjava/java/security/BasicPermission.java

/* BasicPermission.java -- Implements a simple named permission.
   Copyright (C) 1998, 1999 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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General Public License for more details.

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02111-1307 USA.

Linking this library statically or dynamically with other modules is
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */

package java.security;

import java.io.Serializable;
import java.util.Hashtable;
import java.util.Enumeration;

/**
 * This class implements a simple model for named permissions without an
 * associated action list.  That is, either the named permission is granted
 * or it is not.  
 * <p>
 * It also supports trailing wildcards to allow the
 * easy granting of permissions in a hierarchical fashion.  (For example,
 * the name "org.gnu.*" might grant all permissions under the "org.gnu"
 * permissions hierarchy).  The only valid wildcard character is a '*'
 * which matches anything.  It must be the rightmost element in the
 * permission name and must follow a '.' or else the Permission name must
 * consist of only a '*'.  Any other occurrence of a '*' is not valid.
 * <p>
 * This class ignores the action list.  Subclasses can choose to implement
 * actions on top of this class if desired.
 *
 * @version 0.1
 *
 * @author Aaron M. Renn (arenn@urbanophile.com)
 */
public abstract class BasicPermission extends Permission implements
  Serializable
{
  /**
   * This method initializes a new instance of <code>BasicPermission</code>
   * with the specified name.  If the name contains an illegal wildcard
   * character, an exception is thrown.
   *
   * @param name The name of this permission.
   *
   * @exception IllegalArgumentException If the name contains an invalid wildcard character
   * @exception NullPointerException If the name is null
   */
  public BasicPermission(String name) 
    throws IllegalArgumentException, NullPointerException
  {
    super(name);

    if (name.indexOf("*") != -1)
      {
	if (!name.endsWith(".*") && !name.equals("*"))
	  throw new IllegalArgumentException("Bad wildcard: " + name);

	if (name.indexOf("*") != name.lastIndexOf("*"))
	  throw new IllegalArgumentException("Bad wildcard: " + name);
      }
  }

  /**
   * This method initializes a new instance of <code>BasicPermission</code>
   * with the specified name.  If the name contains an illegal wildcard
   * character, an exception is thrown.  The action list passed to this
   * form of the constructor is ignored.
   *
   * @param name The name of this permission.
   * @param actions The list of actions for this permission - ignored in this class.
   *
   * @exception IllegalArgumentException If the name contains an invalid wildcard character
   * @exception NullPointerException If the name is null
   */
  public BasicPermission(String name, String actions) 
    throws IllegalArgumentException, NullPointerException
  {
    // ignore actions
    this(name);
  }

  /**
   * This method tests to see if the specified permission is implied by 
   * this permission.  This will be true if the following conditions are met:
   * <p>
   * <ul>
   * <li>The specified object is an instance of <code>BasicPermission</code>, 
   * or a subclass.
   * <li>The name of the specified permission is identical to this permission's
   * name or the name of the specified permission satisfies a wildcard match 
   * on this permission.
   * </ul>
   *
   * @param perm The <code>Permission</code> object to test against.
   *
   * @return <code>true</code> if the specified permission is implied by this one or <code>false</code> otherwise.
   */
  public boolean implies(Permission perm)
  {
    if (!(perm instanceof BasicPermission))
      return false;

    String otherName = perm.getName();
    String name = getName();

    if (name.equals(otherName))
      return true;

    int last = name.length() - 1;
    if (name.charAt(last) == '*'
	&& otherName.startsWith(name.substring(0, last)))
      return true;

    return false;
  }

  /**
   * This method tests to see if this object is equal to the specified
   * <code>Object</code>.  This will be true if and only if the specified
   * object meets the following conditions:
   * <p>
   * <ul>
   * <li>It is an instance of <code>BasicPermission</code>, or a subclass.
   * <li>It has the same name as this permission.
   * </ul>
   *
   * @param obj The <code>Object</code> to test for equality against this object
   *
   * @return <code>true</code> if the specified <code>Object</code> is equal to this object or <code>false</code> otherwise.
   */
  public boolean equals(Object obj)
  {
    if (!(obj instanceof BasicPermission))
      return (false);

    if (!getName().equals(((BasicPermission) obj).getName()))
      return (false);

    return (true);
  }

  /**
   * This method returns a hash code for this permission object.  The hash
   * code returned is the value returned by calling the <code>hashCode</code>
   * method on the <code>String</code> that is the name of this permission.
   *
   * @return A hash value for this object
   */
  public int hashCode()
  {
    return (getName().hashCode());
  }

  /**
   * This method returns a list of the actions associated with this 
   * permission.  This method always returns the empty string ("") since
   * this class ignores actions.
   *
   * @return The action list.
   */
  public String getActions()
  {
    return ("");
  }

  /**
   * This method returns an instance of <code>PermissionCollection</code>
   * suitable for storing <code>BasicPermission</code> objects.  This returns
   * be a sub class of <code>PermissionCollection</code>
   * that allows for an efficient and consistent implementation of
   * the <code>implies</code> method.  The collection doesn't handle subclasses
   * of BasicPermission correctly; they must override this method. 
   *
   * @return A new empty <code>PermissionCollection</code> object.
   */
  public PermissionCollection newPermissionCollection()
  {
    return new PermissionCollection()
    {
      Hashtable permissions = new Hashtable();
      boolean allAllowed = false;

      public void add(Permission permission)
      {
	if (isReadOnly())
	  throw new IllegalStateException("readonly");

	BasicPermission bp = (BasicPermission) permission;
	String name = bp.getName();
	if (name.equals("*"))
	  allAllowed = true;
	permissions.put(name, bp);
      }

      public boolean implies(Permission permission)
      {
	if (!(permission instanceof BasicPermission))
	  return false;

	if (allAllowed)
	  return true;

	BasicPermission toImply = (BasicPermission) permission;
	String name = toImply.getName();
	if (name.equals("*"))
	  return false;

	int prefixLength = name.length();
	if (name.endsWith("*"))
	  prefixLength -= 2;

	while (true)
	  {
	    if (permissions.get(name) != null)
	      return true;

	    prefixLength = name.lastIndexOf('.', prefixLength);
	    if (prefixLength < 0)
	      return false;
	    name = name.substring(0, prefixLength + 1) + '*';
	  }
      }

      public Enumeration elements()
      {
	return permissions.elements();
      }
    };
  }
}