SquirrelJME/SquirrelJME

// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// 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 java.lang;

import cc.squirreljme.jvm.mle.DebugShelf;
import cc.squirreljme.jvm.mle.RuntimeShelf;
import cc.squirreljme.jvm.mle.brackets.TracePointBracket;
import cc.squirreljme.jvm.mle.constants.StandardPipeType;
import cc.squirreljme.jvm.mle.constants.VMStatisticType;
import cc.squirreljme.runtime.cldc.annotation.Api;
import cc.squirreljme.runtime.cldc.debug.CallTraceUtils;
import cc.squirreljme.runtime.cldc.debug.Debugging;
import cc.squirreljme.runtime.cldc.io.ConsoleOutputStream;
import cc.squirreljme.runtime.cldc.io.NonClosedOutputStream;
import java.io.PrintStream;
import org.jetbrains.annotations.Contract;

/**
 * This class contains information about the host memory environment along
 * with providing methods to perform garbage collection and exit the
 * virtual machine.
 *
 * @since 2018/10/14
 */
@Api
public class Runtime
{
    /** There is only a single instance of the run-time. */
    private static final Runtime _INSTANCE =
        new Runtime();
    
    /**
     * Not used.
     *
     * @since 2018/10/14
     */
    private Runtime()
    {
    }
    
    /**
     * Indicates that the application exits with the given code.
     *
     * @param __v The exit code, the value of this code may change according
     * to the host operating system and the resulting process might not exit
     * with the given code.
     * @throws SecurityException If exiting is not permitted.
     * @since 2017/02/08
     */
    @Api
    @Contract("_ -> fail")
    public void exit(int __v)
        throws SecurityException
    {
        // Check that we can exit
        System.getSecurityManager().checkExit(__v);
        
        // Indicate that the VM is exiting
        try
        {
            Debugging.debugNote("Exiting VM with %d...", __v);
            
            // Print the trace where this exit is for debugging
            if (__v != 0)
            {
                TracePointBracket[] trace = DebugShelf.traceStack();
                CallTraceUtils.printStackTrace(new PrintStream(
                        new NonClosedOutputStream(
                            new ConsoleOutputStream(StandardPipeType.STDERR,
                                true))),
                    "EXIT", trace,
                    null, null, 0);
            }
        }
        catch (Throwable ignored)
        {
        }
        
        // Then do the exit if no exception was thrown
        RuntimeShelf.exit(__v);
    }
    
    /**
     * Returns the amount of memory that is free for the JVM to use.
     *
     * @return The amount of free memory.
     * @since 2018/10/14
     */
    @Api
    public long freeMemory()
    {
        return RuntimeShelf.vmStatistic(VMStatisticType.MEM_FREE);
    }
    
    /**
     * Indicates that the application should have garbage collection be
     * performed. It is unspecified when garbage collection occurs.
     *
     * @since 2017/02/08
     */
    @Api
    public void gc()
    {
        RuntimeShelf.garbageCollect();
    }
    
    /**
     * Returns the maximum amount of memory that the virtual machine will
     * attempt to use, if there is no limit then {@link Long#MAX_VALUE} will
     * be used.
     *
     * @return The maximum amount of memory available to the virtual machine.
     * @since 2018/10/14
     */
    @Api
    public long maxMemory()
    {
        return RuntimeShelf.vmStatistic(VMStatisticType.MEM_MAX);
    }
    
    /**
     * Returns the total amount of memory that is being used by the virtual
     * machine. This is a count of all the memory claimed by the virtual
     * machine itself for its memory pools and such.
     *
     * @return The amount of memory being used by the virtual machine.
     * @since 2018/10/14
     */
    @Api
    public long totalMemory()
    {
        return RuntimeShelf.vmStatistic(VMStatisticType.MEM_USED);
    }
    
    /**
     * Returns the single instance of this class.
     *
     * Only a single runtime is valid and there will only be one.
     *
     * @return The current run-time.
     * @since 2018/03/01
     */
    @Api
    public static Runtime getRuntime()
    {
        return Runtime._INSTANCE;
    }
}