SquirrelJME/SquirrelJME

// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// Multi-Phasic Applications: SquirrelJME
//     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
// ---------------------------------------------------------------------------
// SquirrelJME is under the Mozilla Public License Version 2.0.
// See license.mkd for licensing and copyright information.
// ---------------------------------------------------------------------------

package javax.microedition.lcdui;

import cc.squirreljme.runtime.cldc.debug.Debugging;

/**
 * Lock for the layout.
 *
 * @since 2022/07/20
 */
final class __LayoutLock__
    implements AutoCloseable
{
    /** The thread that is locking. */
    private volatile Thread _thread;
    
    /** The number of usages. */
    private volatile int _useCount; 
    
    /**
     * Locks the layout.
     * 
     * @since 2022/07/20
     */
    public void lock()
    {
        Thread current = Thread.currentThread();
        synchronized (this)
        {
            for (;;)
            {
                Thread thread = this._thread;
                
                // Do nothing if we locked it
                if (thread == current)
                    return;
                
                // Claim it if it is free
                else if (thread == null)
                {
                    this._thread = current;
                    return;
                }
                
                // Otherwise, wait until it gets free
                try
                {
                    this.wait(1000);
                }
                catch (InterruptedException ignored)
                {
                }
            }
        }
    }
    
    /**
     * {@inheritDoc}
     * @since 2022/07/20
     */
    @Override
    public void close()
    {
        // Performs the opposite of utilize
        synchronized (this)
        {
            /* {@squirreljme.error EB35 Form layout update called outside
            permitted method.} */
            if (this._thread != Thread.currentThread())
                throw new IllegalStateException("EB35");
            
            // Utilize down
            this._useCount = Math.max(0, this._useCount - 1);
        }
    }
    
    /**
     * Utilizes the lock.
     * 
     * @throws IllegalStateException If this was called outside of the
     * permitted methods.
     * @since 2022/07/20
     */
    public __LayoutLock__ utilize()
        throws IllegalStateException
    {
        synchronized (this)
        {
            /* {@squirreljme.error EB34 Form layout update called outside
            permitted method.} */
            if (this._thread != Thread.currentThread())
                throw new IllegalStateException("EB34");
            
            // Utilize up
            this._useCount++;
        }
        
        // Self always
        return this;
    } 
    
    /**
     * Unlocks the layout.
     * 
     * @since 2022/07/20
     */
    public void unlock()
    {
        Thread current = Thread.currentThread();
        synchronized (this)
        {
            Thread thread = this._thread;
            
            // Ignore if not our own thread
            if (thread != current)
                return;
            
            // Otherwise, reset it
            this._thread = null;
            this._useCount = 0;
            
            // Notify anything waiting for an unlock that it actually
            // happened!
            this.notifyAll();
        }
    }
}