AccessControlContext.java   [plain text]

/* AccessControlContext.java --- Access Control Context Class
   Copyright (C) 1999, 2004 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
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
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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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or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
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exception statement from your version. */

package java.security;

/**
 * AccessControlContext makes system resource access decsion 
 * based on permission rights.  
 *
 * It is used for a specific context and has only one method
 * checkPermission. It is similar to AccessController except
 * that it makes decsions based on the current context instead
 * of the the current thread.
 *
 * It is created by call AccessController.getContext method.
 *
 * @author Mark Benvenuto
 * @since 1.2
 */
public final class AccessControlContext
{
  private ProtectionDomain protectionDomain[];
  private DomainCombiner combiner;

  /**
   * Construct a new AccessControlContext with the specified
   * ProtectionDomains. <code>context</code> must not be 
   * null and duplicates will be removed.
   *
   * @param context The ProtectionDomains to use
   */
  public AccessControlContext(ProtectionDomain[]context)
  {
    int i, j, k, count = context.length, count2 = 0;
    for (i = 0, j = 0; i < count; i++)
      {
	for (k = 0; k < i; k++)
	  if (context[k] == protectionDomain[i])
	    break;
	if (k != i)		//it means previous loop did not complete
	  continue;

	count2++;
      }

    protectionDomain = new ProtectionDomain[count2];
    for (i = 0, j = 0; i < count2; i++)
      {
	for (k = 0; k < i; k++)
	  if (context[k] == protectionDomain[i])
	    break;
	if (k != i)		//it means previous loop did not complete
	  continue;

	protectionDomain[j++] = context[i];
      }
  }

  /**
   * Construct a new AccessControlContext with the specified
   * ProtectionDomains and DomainCombiner
   *
   * @since 1.3
   */
  public AccessControlContext(AccessControlContext acc,
			      DomainCombiner combiner)
  {
    this(acc.protectionDomain);
    this.combiner = combiner;
  }

  /**
   * Returns the Domain Combiner associated with the AccessControlContext
   *
   * @return the DomainCombiner
   */
  public DomainCombiner getDomainCombiner()
  {
    return combiner;
  }

  /**
   * Determines whether or not the specific permission is granted
   * depending on the context it is within. 
   *
   * @param perm a permission to check
   *
   * @throws AccessControlException if the permssion is not permitted
   */
  public void checkPermission(Permission perm) throws AccessControlException
  {
    for (int i = 0; i < protectionDomain.length; i++)
      if (protectionDomain[i].implies(perm) == true)
	return;

    throw new AccessControlException("Permission not granted");
  }

  /**
   * Checks if two AccessControlContexts are equal.
   *
   * It first checks if obj is an AccessControlContext class, and
   * then checks if each ProtectionDomain matches.
   *
   * @param obj The object to compare this class to
   *
   * @return true if equal, false otherwise
   */
  public boolean equals(Object obj)
  {
    if (obj instanceof AccessControlContext)
      {
	AccessControlContext acc = (AccessControlContext) obj;

	if (acc.protectionDomain.length != protectionDomain.length)
	  return false;

	for (int i = 0; i < protectionDomain.length; i++)
	  if (acc.protectionDomain[i] != protectionDomain[i])
	    return false;
	return true;
      }
    return false;
  }

  /**
   * Computes a hash code of this class
   *
   * @return a hash code representing this class
   */
  public int hashCode()
  {
    int h = 0;
    for (int i = 0; i < protectionDomain.length; i++)
      h ^= protectionDomain[i].hashCode();

    return h;
  }
}