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	/*
	* Copyright (c) 1996, 2020, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code 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
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package jdk.internal.misc;

	import static java.lang.Thread.State.*;

	import java.text.NumberFormat;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.List;
	import java.util.Map;

	import jdk.internal.access.SharedSecrets;

	import sun.nio.ch.FileChannelImpl;

	public class VM {

	// the init level when the VM is fully initialized
	private static final int JAVA_LANG_SYSTEM_INITED = 1;
	private static final int MODULE_SYSTEM_INITED = 2;
	private static final int SYSTEM_LOADER_INITIALIZING = 3;
	private static final int SYSTEM_BOOTED = 4;
	private static final int SYSTEM_SHUTDOWN = 5;

	// 0, 1, 2, ...
	private static volatile int initLevel;
	private static final Object lock = new Object();

	/**
	* Sets the init level.
	*
	* @see java.lang.System#initPhase1
	* @see java.lang.System#initPhase2
	* @see java.lang.System#initPhase3
	*/
	public static void initLevel(int value) {
	synchronized (lock) {
	if (value <= initLevel \|\| value > SYSTEM_SHUTDOWN)
	throw new InternalError("Bad level: " + value);
	initLevel = value;
	lock.notifyAll();
	}
	}

	/**
	* Returns the current init level.
	*/
	public static int initLevel() {
	return initLevel;
	}

	/**
	* Waits for the init level to get the given value.
	*
	* @see java.lang.ref.Finalizer
	*/
	public static void awaitInitLevel(int value) throws InterruptedException {
	synchronized (lock) {
	while (initLevel < value) {
	lock.wait();
	}
	}
	}

	/**
	* Returns {@code true} if the module system has been initialized.
	* @see java.lang.System#initPhase2
	*/
	public static boolean isModuleSystemInited() {
	return VM.initLevel() >= MODULE_SYSTEM_INITED;
	}

	/**
	* Returns {@code true} if the VM is fully initialized.
	*/
	public static boolean isBooted() {
	return initLevel >= SYSTEM_BOOTED;
	}

	/**
	* Set shutdown state. Shutdown completes when all registered shutdown
	* hooks have been run.
	*
	* @see java.lang.Shutdown
	*/
	public static void shutdown() {
	initLevel(SYSTEM_SHUTDOWN);
	}

	/**
	* Returns {@code true} if the VM has been shutdown
	*/
	public static boolean isShutdown() {
	return initLevel == SYSTEM_SHUTDOWN;
	}

	// A user-settable upper limit on the maximum amount of allocatable direct
	// buffer memory. This value may be changed during VM initialization if
	// "java" is launched with "-XX:MaxDirectMemorySize=<size>".
	//
	// The initial value of this field is arbitrary; during JRE initialization
	// it will be reset to the value specified on the command line, if any,
	// otherwise to Runtime.getRuntime().maxMemory().
	//
	private static long directMemory = 64 * 1024 * 1024;

	// Returns the maximum amount of allocatable direct buffer memory.
	// The directMemory variable is initialized during system initialization
	// in the saveAndRemoveProperties method.
	//
	public static long maxDirectMemory() {
	return directMemory;
	}

	// User-controllable flag that determines if direct buffers should be page
	// aligned. The "-XX:+PageAlignDirectMemory" option can be used to force
	// buffers, allocated by ByteBuffer.allocateDirect, to be page aligned.
	private static boolean pageAlignDirectMemory;

	// Returns {@code true} if the direct buffers should be page aligned. This
	// variable is initialized by saveAndRemoveProperties.
	public static boolean isDirectMemoryPageAligned() {
	return pageAlignDirectMemory;
	}

	private static int classFileMajorVersion;
	private static int classFileMinorVersion;
	private static final int PREVIEW_MINOR_VERSION = 65535;

	/**
	* Tests if the given version is a supported {@code class}
	* file version.
	*
	* A {@code class} file depends on the preview features of Java SE {@code N}
	* if the major version is {@code N} and the minor version is 65535.
	* This method returns {@code true} if the given version is a supported
	* {@code class} file version regardless of whether the preview features
	* are enabled or not.
	*
	* @jvms 4.1 Table 4.1-A. class file format major versions
	*/
	public static boolean isSupportedClassFileVersion(int major, int minor) {
	if (major < 45 \|\| major > classFileMajorVersion) return false;
	// for major version is between 45 and 55 inclusive, the minor version may be any value
	if (major < 56) return true;
	// otherwise, the minor version must be 0 or 65535
	return minor == 0 \|\| minor == PREVIEW_MINOR_VERSION;
	}

	/**
	* Tests if the given version is a supported {@code class}
	* file version for module descriptor.
	*
	* major.minor version >= 53.0
	*/
	public static boolean isSupportedModuleDescriptorVersion(int major, int minor) {
	if (major < 53 \|\| major > classFileMajorVersion) return false;
	// for major version is between 45 and 55 inclusive, the minor version may be any value
	if (major < 56) return true;
	// otherwise, the minor version must be 0 or 65535
	// preview features do not apply to module-info.class but JVMS allows it
	return minor == 0 \|\| minor == PREVIEW_MINOR_VERSION;
	}

	/**
	* Returns true if the given class loader is the bootstrap class loader
	* or the platform class loader.
	*/
	public static boolean isSystemDomainLoader(ClassLoader loader) {
	return loader == null \|\| loader == ClassLoader.getPlatformClassLoader();
	}

	/**
	* Returns the system property of the specified key saved at
	* system initialization time. This method should only be used
	* for the system properties that are not changed during runtime.
	*
	* Note that the saved system properties do not include
	* the ones set by java.lang.VersionProps.init().
	*/
	public static String getSavedProperty(String key) {
	if (savedProps == null)
	throw new IllegalStateException("Not yet initialized");

	return savedProps.get(key);
	}

	/**
	* Gets an unmodifiable view of the system properties saved at system
	* initialization time. This method should only be used
	* for the system properties that are not changed during runtime.
	*
	* Note that the saved system properties do not include
	* the ones set by java.lang.VersionProps.init().
	*/
	public static Map<String, String> getSavedProperties() {
	if (savedProps == null)
	throw new IllegalStateException("Not yet initialized");

	return Collections.unmodifiableMap(savedProps);
	}

	private static Map<String, String> savedProps;

	// Save a private copy of the system properties and remove
	// the system properties that are not intended for public access.
	//
	// This method can only be invoked during system initialization.
	public static void saveProperties(Map<String, String> props) {
	if (initLevel() != 0)
	throw new IllegalStateException("Wrong init level");

	// only main thread is running at this time, so savedProps and
	// its content will be correctly published to threads started later
	if (savedProps == null) {
	savedProps = props;
	}

	// Set the maximum amount of direct memory. This value is controlled
	// by the vm option -XX:MaxDirectMemorySize=<size>.
	// The maximum amount of allocatable direct buffer memory (in bytes)
	// from the system property sun.nio.MaxDirectMemorySize set by the VM.
	// If not set or set to -1, the max memory will be used
	// The system property will be removed.
	String s = props.get("sun.nio.MaxDirectMemorySize");
	if (s == null \|\| s.isEmpty() \|\| s.equals("-1")) {
	// -XX:MaxDirectMemorySize not given, take default
	directMemory = Runtime.getRuntime().maxMemory();
	} else {
	long l = Long.parseLong(s);
	if (l > -1)
	directMemory = l;
	}

	// Check if direct buffers should be page aligned
	s = props.get("sun.nio.PageAlignDirectMemory");
	if ("true".equals(s))
	pageAlignDirectMemory = true;

	s = props.get("java.class.version");
	int index = s.indexOf('.');
	try {
	classFileMajorVersion = Integer.valueOf(s.substring(0, index));
	classFileMinorVersion = Integer.valueOf(s.substring(index+1, s.length()));
	} catch (NumberFormatException e) {
	throw new InternalError(e);
	}
	}

	// Initialize any miscellaneous operating system settings that need to be
	// set for the class libraries.
	//
	public static void initializeOSEnvironment() {
	if (initLevel() == 0) {
	OSEnvironment.initialize();
	}
	}

	/* Current count of objects pending for finalization */
	private static volatile int finalRefCount;

	/* Peak count of objects pending for finalization */
	private static volatile int peakFinalRefCount;

	/*
	* Gets the number of objects pending for finalization.
	*
	* @return the number of objects pending for finalization.
	*/
	public static int getFinalRefCount() {
	return finalRefCount;
	}

	/*
	* Gets the peak number of objects pending for finalization.
	*
	* @return the peak number of objects pending for finalization.
	*/
	public static int getPeakFinalRefCount() {
	return peakFinalRefCount;
	}

	/*
	* Add {@code n} to the objects pending for finalization count.
	*
	* @param n an integer value to be added to the objects pending
	* for finalization count
	*/
	public static void addFinalRefCount(int n) {
	// The caller must hold lock to synchronize the update.

	finalRefCount += n;
	if (finalRefCount > peakFinalRefCount) {
	peakFinalRefCount = finalRefCount;
	}
	}

	/**
	* Returns Thread.State for the given threadStatus
	*/
	public static Thread.State toThreadState(int threadStatus) {
	if ((threadStatus & JVMTI_THREAD_STATE_RUNNABLE) != 0) {
	return RUNNABLE;
	} else if ((threadStatus & JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER) != 0) {
	return BLOCKED;
	} else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_INDEFINITELY) != 0) {
	return WAITING;
	} else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT) != 0) {
	return TIMED_WAITING;
	} else if ((threadStatus & JVMTI_THREAD_STATE_TERMINATED) != 0) {
	return TERMINATED;
	} else if ((threadStatus & JVMTI_THREAD_STATE_ALIVE) == 0) {
	return NEW;
	} else {
	return RUNNABLE;
	}
	}

	/* The threadStatus field is set by the VM at state transition
	* in the hotspot implementation. Its value is set according to
	* the JVM TI specification GetThreadState function.
	*/
	private static final int JVMTI_THREAD_STATE_ALIVE = 0x0001;
	private static final int JVMTI_THREAD_STATE_TERMINATED = 0x0002;
	private static final int JVMTI_THREAD_STATE_RUNNABLE = 0x0004;
	private static final int JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER = 0x0400;
	private static final int JVMTI_THREAD_STATE_WAITING_INDEFINITELY = 0x0010;
	private static final int JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT = 0x0020;

	/*
	* Returns the first user-defined class loader up the execution stack,
	* or the platform class loader if only code from the platform or
	* bootstrap class loader is on the stack.
	*/
	public static ClassLoader latestUserDefinedLoader() {
	ClassLoader loader = latestUserDefinedLoader0();
	return loader != null ? loader : ClassLoader.getPlatformClassLoader();
	}

	/*
	* Returns the first user-defined class loader up the execution stack,
	* or null if only code from the platform or bootstrap class loader is
	* on the stack. VM does not keep a reference of platform loader and so
	* it returns null.
	*
	* This method should be replaced with StackWalker::walk and then we can
	* remove the logic in the VM.
	*/
	private static native ClassLoader latestUserDefinedLoader0();

	/**
	* Returns {@code true} if we are in a set UID program.
	*/
	public static boolean isSetUID() {
	long uid = getuid();
	long euid = geteuid();
	long gid = getgid();
	long egid = getegid();
	return uid != euid \|\| gid != egid;
	}

	/**
	* Returns the real user ID of the calling process,
	* or -1 if the value is not available.
	*/
	public static native long getuid();

	/**
	* Returns the effective user ID of the calling process,
	* or -1 if the value is not available.
	*/
	public static native long geteuid();

	/**
	* Returns the real group ID of the calling process,
	* or -1 if the value is not available.
	*/
	public static native long getgid();

	/**
	* Returns the effective group ID of the calling process,
	* or -1 if the value is not available.
	*/
	public static native long getegid();

	/**
	* Get a nanosecond time stamp adjustment in the form of a single long.
	*
	* This value can be used to create an instant using
	* {@link java.time.Instant#ofEpochSecond(long, long)
	* java.time.Instant.ofEpochSecond(offsetInSeconds,
	* getNanoTimeAdjustment(offsetInSeconds))}.
	* <p>
	* The value returned has the best resolution available to the JVM on
	* the current system.
	* This is usually down to microseconds - or tenth of microseconds -
	* depending on the OS/Hardware and the JVM implementation.
	*
	* @param offsetInSeconds The offset in seconds from which the nanosecond
	* time stamp should be computed.
	*
	* @apiNote The offset should be recent enough - so that
	* {@code offsetInSeconds} is within {@code +/- 2^32} seconds of the
	* current UTC time. If the offset is too far off, {@code -1} will be
	* returned. As such, {@code -1} must not be considered as a valid
	* nano time adjustment, but as an exception value indicating
	* that an offset closer to the current time should be used.
	*
	* @return A nanosecond time stamp adjustment in the form of a single long.
	* If the offset is too far off the current time, this method returns -1.
	* In that case, the caller should call this method again, passing a
	* more accurate offset.
	*/
	public static native long getNanoTimeAdjustment(long offsetInSeconds);

	/**
	* Returns the VM arguments for this runtime environment.
	*
	* @implNote
	* The HotSpot JVM processes the input arguments from multiple sources
	* in the following order:
	* 1. JAVA_TOOL_OPTIONS environment variable
	* 2. Options from JNI Invocation API
	* 3. _JAVA_OPTIONS environment variable
	*
	* If VM options file is specified via -XX:VMOptionsFile, the vm options
	* file is read and expanded in place of -XX:VMOptionFile option.
	*/
	public static native String[] getRuntimeArguments();

	static {
	initialize();
	}
	private static native void initialize();

	/**
	* Provides access to information on buffer usage.
	*/
	public interface BufferPool {
	String getName();
	long getCount();
	long getTotalCapacity();
	long getMemoryUsed();
	}

	private static class BufferPoolsHolder {
	static final List<BufferPool> BUFFER_POOLS;

	static {
	ArrayList<BufferPool> bufferPools = new ArrayList<>(3);
	bufferPools.add(SharedSecrets.getJavaNioAccess().getDirectBufferPool());
	bufferPools.add(FileChannelImpl.getMappedBufferPool());
	bufferPools.add(FileChannelImpl.getSyncMappedBufferPool());

	BUFFER_POOLS = Collections.unmodifiableList(bufferPools);
	}
	}

	/**
	* @return the list of buffer pools.
	*/
	public static List<BufferPool> getBufferPools() {
	return BufferPoolsHolder.BUFFER_POOLS;
	}
	}

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