# AssociatedThread.java

    /*
    ** Module   : AssociatedThread.java
    ** Abstract : a new thread which inherits the security context of the creating thread
    **
    ** Copyright (c) 2011-2023, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- -----------------------Description------------------------
    ** 001 GES 20111109 First version.
    ** 002 GES 20200204 Refactored some logic into a base class.
    ** 003 GBB 20230825 SecurityManager context methods calls updated.
    */

    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program 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 Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
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    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
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    **
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    */

    package com.goldencode.p2j.security;

    /**
     * Provides a thread which automatically inherits the security context of the thread that
     * instantiates it.  This means that the SAME context is used on both the instantiating thread
     * and the new thread.  All context-local data is accessible to both threads.  When the thread
     * exits, it will automatically cleanup the context (decrementing the reference counts and so
     * forth). This makes it easy to implement additional threads which all share the same
     * context, which means they have the same rights and have the same context-local data.
     * <p>
     * <b>WARNING:</b> Be very careful using this mechanism.  Much (if not all of) the context-local
     * data may not be thread-safe.  Any data sharing between threads sharing a context must be made
     * safe by the caller.
     */
    public class AssociatedThread
    extends ContextAwareThread
    {
       /** Any pending security context switch or {@code null}. */
       private SecurityContext context = null;

       /**
        * Constructor which allows the core logic to be specified.
        *
        * @param    core
        *           The logic to execute when the thread is started.  Must not be {@code null}.
        *
        * @throws   NullPointerException
        *           If the instantiating thread has no security context or if {@code core} is
        *           {@code null}.
        */
       public AssociatedThread(Runnable core)
       throws NullPointerException
       {
          // duplicate the current context stack (which has both the initial and optionally an
          // effective context assigned)
          super(core, sm.isServer() ? SecurityContextStack.getContext().duplicate() : null);
       }

       /**
        * Save the given context as a pending context switch which will be
        * processed later by the key reading thread.
        *
        * @param    context
        *           The security context to switch to (if non-null).
        */
       public synchronized void setPendingContextSwitch(Object context)
       {
          if (context != null && context instanceof SecurityContext)
          {
             this.context = (SecurityContext) context;
          }
       }

       /**
        * Switch security contexts on the current thread if a switch is pending.
        */
       public synchronized void morphContextIfNeeded()
       {
          if (context != null)
          {
             if (sm.isServer())
             {
                try
                {
                   sm.contextSm.pushContextWorker(context);
                }

                catch (RestrictedUseException rue)
                {
                   // should not happen
                }
             }

             context = null;
          }
       }
    }