Initial revision

From-SVN: r102074

libjava/classpath/java/security/Permissions.java

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+/* Permissions.java -- a collection of permission collections
+   Copyright (C) 1998, 2001, 2002, 2004, 2005  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.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 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
+combination.
+
+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
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+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
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.security;
+
+import java.io.Serializable;
+import java.util.Enumeration;
+import java.util.Hashtable;
+import java.util.NoSuchElementException;
+
+/**
+ * This class is a heterogeneous collection of permissions.  It is
+ * organized as a collection of <code>PermissionCollection</code>'s stored
+ * in a hashtable.  Each individual <code>PermissionCollection</code>
+ * contains permissions of a single type.  If a specific type of
+ * <code>Permission</code> does not provide a collection type to use
+ * via its <code>newPermissionCollection</code> method, then a default
+ * collection type which stores its permissions in a hash table will be
+ * used.
+ *
+ * @author Aaron M. Renn (arenn@urbanophile.com)
+ * @author Eric Blake (ebb9@email.byu.edu)
+ * @since 1.1
+ */
+public final class Permissions extends PermissionCollection
+  implements Serializable
+{
+  /**
+   * Compatible with JDK 1.1+.
+   */
+  private static final long serialVersionUID = 4858622370623524688L;
+
+  /**
+   * Holds instances of <code>AllPermission</code>.
+   *
+   * @serial the permission collection for AllPermission
+   */
+  private PermissionCollection allPermission;
+
+  // Package-private to avoid a trampoline.
+  /**
+   * This is the <code>Hashtable</code> that contains our collections.
+   *
+   * @serial maps Class to PermissionCollection
+   */
+  final Hashtable perms = new Hashtable();
+
+  /**
+   * This method initializes a new instance of <code>Permissions</code>.
+   */
+  public Permissions()
+  {
+  }
+
+  /**
+   * This method adds a new <code>Permission</code> to this collection.  It
+   * will be stored in a <code>PermissionCollection</code> of the appropriate
+   * type, as determined by calling <code>newPermissionCollection</code> on
+   * the specified permission (if an appropriate collection does not already
+   * exist). If this object does not specify a particular type of collection,
+   * a default collection, which stores in permissions in a hash table, will
+   * be used.
+   *
+   * @param perm the <code>Permission</code> to add
+   * @throws SecurityException if this collection is marked as read only
+   */
+  public void add(Permission perm)
+  {
+    if (isReadOnly())
+      throw new SecurityException("PermissionCollection is read only");
+    if (perm instanceof AllPermission)
+      {
+        if (allPermission == null)
+          {
+            allPermission = perm.newPermissionCollection();
+            allPermission.add(perm);
+            perms.put(perm.getClass(), allPermission);
+          }
+      }
+    else
+      {
+        PermissionCollection pc
+          = (PermissionCollection) perms.get(perm.getClass());
+        if (pc == null)
+          {
+            pc = perm.newPermissionCollection();
+            if (pc == null)
+              pc = new PermissionsHash();
+            perms.put(perm.getClass(), pc);
+          }
+        pc.add(perm);
+      }
+  }
+
+  /**
+   * This method tests whether or not the specified <code>Permission</code>
+   * is implied by this <code>PermissionCollection</code>.
+   *
+   * @param perm the <code>Permission</code> to test
+   * @return true if the specified permission is implied by this
+   */
+  public boolean implies(Permission perm)
+  {
+    if (allPermission != null)
+      return true;
+    PermissionCollection pc
+      = (PermissionCollection) perms.get(perm.getClass());
+    return pc == null ? false : pc.implies(perm);
+  }
+
+  /**
+   * This method returns an <code>Enumeration</code> which contains a
+   * list of all <code>Permission</code> objects contained in this
+   * collection.
+   *
+   * @return an <code>Enumeration</code> of this collection's elements
+   */
+  public Enumeration elements()
+  {
+    return new Enumeration()
+    {
+      Enumeration main_enum = perms.elements();
+      Enumeration sub_enum;
+
+      public boolean hasMoreElements()
+      {
+        if (sub_enum == null)
+          {
+            if (main_enum == null)
+              return false;
+            if (! main_enum.hasMoreElements())
+              {
+                main_enum = null;
+                return false;
+              }
+            PermissionCollection pc =
+              (PermissionCollection) main_enum.nextElement();
+            sub_enum = pc.elements();
+          }
+        if (! sub_enum.hasMoreElements())
+          {
+            sub_enum = null;
+            return hasMoreElements();
+          }
+        return true;
+      }
+
+      public Object nextElement()
+      {
+        if (! hasMoreElements())
+          throw new NoSuchElementException();
+        return sub_enum.nextElement();
+      }
+    };
+  }
+
+  /**
+   * Implements the permission collection for all permissions without one of
+   * their own, and obeys serialization of JDK.
+   *
+   * @author Eric Blake (ebb9@email.byu.edu)
+   */
+  private static final class PermissionsHash extends PermissionCollection
+  {
+    /**
+     * Compatible with JDK 1.1+.
+     */
+    private static final long serialVersionUID = -8491988220802933440L;
+
+    /**
+     * Hashtable where we store permissions.
+     *
+     * @serial the stored permissions, both as key and value
+     */
+    private final Hashtable perms = new Hashtable();
+
+    /**
+     * Add a permission. We don't need to check for read-only, as this
+     * collection is never exposed outside of Permissions, which has already
+     * done that check.
+     *
+     * @param perm the permission to add
+     */
+    public void add(Permission perm)
+    {
+      perms.put(perm, perm);
+    }
+
+    /**
+     * Returns true if perm is in the collection.
+     *
+     * @param perm the permission to check
+     * @return true if it is implied
+     */
+    // FIXME: Should this method be synchronized?
+    public boolean implies(Permission perm)
+    {
+      Enumeration elements = elements();
+      
+      while (elements.hasMoreElements())
+	{
+	  Permission p = (Permission)elements.nextElement();
+	  if (p.implies(perm))
+	    return true;
+	}
+      return false;
+    }
+
+    /**
+     * Return the elements.
+     *
+     * @return the elements
+     */
+    public Enumeration elements()
+    {
+      return perms.elements();
+    }
+  } // class PermissionsHash
+} // class Permissions