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	/*
	* Copyright (c) 2002, 2006, 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 sun.misc;

	import java.nio.ByteBuffer;
	import java.security.Permission;
	import java.security.PrivilegedAction;
	import java.io.IOException;
	import java.io.UnsupportedEncodingException;

	/**
	* The Perf class provides the ability to attach to an instrumentation
	* buffer maintained by a Java virtual machine. The instrumentation
	* buffer may be for the Java virtual machine running the methods of
	* this class or it may be for another Java virtual machine on the
	* same system.
	* <p>
	* In addition, this class provides methods to create instrumentation
	* objects in the instrumentation buffer for the Java virtual machine
	* that is running these methods. It also contains methods for acquiring
	* the value of a platform specific high resolution clock for time
	* stamp and interval measurement purposes.
	*
	* @author Brian Doherty
	* @since 1.4.2
	* @see #getPerf
	* @see sun.misc.Perf$GetPerfAction
	* @see java.nio.ByteBuffer
	*/
	public final class Perf {

	private static Perf instance;

	private static final int PERF_MODE_RO = 0;
	private static final int PERF_MODE_RW = 1;

	private Perf() { } // prevent instantiation

	/**
	* The GetPerfAction class is a convenience class for acquiring access
	* to the singleton Perf instance using the
	* <code>AccessController.doPrivileged()</code> method.
	* <p>
	* An instance of this class can be used as the argument to
	* <code>AccessController.doPrivileged(PrivilegedAction)</code>.
	* <p> Here is a suggested idiom for use of this class:
	*
	* <blockquote><pre>
	* class MyTrustedClass {
	* private static final Perf perf =
	* AccessController.doPrivileged(new Perf.GetPerfAction<Perf>());
	* ...
	* }
	* </pre></blockquote>
	* <p>
	* In the presence of a security manager, the <code>MyTrustedClass</code>
	* class in the above example will need to be granted the
	* <em>"sun.misc.Perf.getPerf"</em> <code>RuntimePermission</code>
	* permission in order to successfully acquire the singleton Perf instance.
	* <p>
	* Please note that the <em>"sun.misc.Perf.getPerf"</em> permission
	* is not a JDK specified permission.
	*
	* @see java.security.AccessController#doPrivileged(PrivilegedAction)
	* @see java.lang.RuntimePermission
	*/
	public static class GetPerfAction implements PrivilegedAction<Perf>
	{
	/**
	* Run the <code>Perf.getPerf()</code> method in a privileged context.
	*
	* @see #getPerf
	*/
	public Perf run() {
	return getPerf();
	}
	}

	/**
	* Return a reference to the singleton Perf instance.
	* <p>
	* The getPerf() method returns the singleton instance of the Perf
	* class. The returned object provides the caller with the capability
	* for accessing the instrumentation buffer for this or another local
	* Java virtual machine.
	* <p>
	* If a security manager is installed, its <code>checkPermission</code>
	* method is called with a <code>RuntimePermission</code> with a target
	* of <em>"sun.misc.Perf.getPerf"</em>. A security exception will result
	* if the caller has not been granted this permission.
	* <p>
	* Access to the returned <code>Perf</code> object should be protected
	* by its caller and not passed on to untrusted code. This object can
	* be used to attach to the instrumentation buffer provided by this Java
	* virtual machine or for those of other Java virtual machines running
	* on the same system. The instrumentation buffer may contain senstitive
	* information. API's built on top of this interface may want to provide
	* finer grained access control to the contents of individual
	* instrumentation objects contained within the buffer.
	* <p>
	* Please note that the <em>"sun.misc.Perf.getPerf"</em> permission
	* is not a JDK specified permission.
	*
	* @return A reference to the singleton Perf instance.
	* @throws AccessControlException if a security manager exists and
	* its <code>checkPermission</code> method doesn't allow
	* access to the <em>"sun.misc.Perf.getPerf"</em> target.
	* @see java.lang.RuntimePermission
	* @see #attach
	*/
	public static Perf getPerf()
	{
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	Permission perm = new RuntimePermission("sun.misc.Perf.getPerf");
	security.checkPermission(perm);
	}

	return instance;
	}

	/**
	* Attach to the instrumentation buffer for the specified Java virtual
	* machine.
	* <p>
	* This method will attach to the instrumentation buffer for the
	* specified virtual machine. It returns a <code>ByteBuffer</code> object
	* that is initialized to access the instrumentation buffer for the
	* indicated Java virtual machine. The <code>lvmid</code> parameter is
	* a integer value that uniquely identifies the target local Java virtual
	* machine. It is typically, but not necessarily, the process id of
	* the target Java virtual machine.
	* <p>
	* If the <code>lvmid</code> identifies a Java virtual machine different
	* from the one running this method, then the coherency characteristics
	* of the buffer are implementation dependent. Implementations that do
	* not support named, coherent, shared memory may return a
	* <code>ByteBuffer</code> object that contains only a snap shot of the
	* data in the instrumentation buffer. Implementations that support named,
	* coherent, shared memory, may return a <code>ByteBuffer</code> object
	* that will be changing dynamically over time as the target Java virtual
	* machine updates its mapping of this buffer.
	* <p>
	* If the <code>lvmid</code> is 0 or equal to the actual <code>lvmid</code>
	* for the Java virtual machine running this method, then the returned
	* <code>ByteBuffer</code> object will always be coherent and dynamically
	* changing.
	* <p>
	* The attach mode specifies the access permissions requested for the
	* instrumentation buffer of the target virtual machine. The permitted
	* access permissions are:
	* <p>
	* <bl>
	* <li>"r" - Read only access. This Java virtual machine has only
	* read access to the instrumentation buffer for the target Java
	* virtual machine.
	* <li>"rw" - Read/Write access. This Java virtual machine has read and
	* write access to the instrumentation buffer for the target Java virtual
	* machine. This mode is currently not supported and is reserved for
	* future enhancements.
	* </bl>
	*
	* @param lvmid an integer that uniquely identifies the
	* target local Java virtual machine.
	* @param mode a string indicating the attach mode.
	* @return ByteBuffer a direct allocated byte buffer
	* @throws IllegalArgumentException The lvmid or mode was invalid.
	* @throws IOException An I/O error occurred while trying to acquire
	* the instrumentation buffer.
	* @throws OutOfMemoryError The instrumentation buffer could not be mapped
	* into the virtual machine's address space.
	* @see java.nio.ByteBuffer
	*/
	public ByteBuffer attach(int lvmid, String mode)
	throws IllegalArgumentException, IOException
	{
	if (mode.compareTo("r") == 0) {
	return attachImpl(null, lvmid, PERF_MODE_RO);
	}
	else if (mode.compareTo("rw") == 0) {
	return attachImpl(null, lvmid, PERF_MODE_RW);
	}
	else {
	throw new IllegalArgumentException("unknown mode");
	}
	}

	/**
	* Attach to the instrumentation buffer for the specified Java virtual
	* machine owned by the given user.
	* <p>
	* This method behaves just as the <code>attach(int lvmid, String mode)
	* </code> method, except that it only searches for Java virtual machines
	* owned by the specified user.
	*
	* @param user A <code>String</code> object containing the
	* name of the user that owns the target Java
	* virtual machine.
	* @param lvmid an integer that uniquely identifies the
	* target local Java virtual machine.
	* @param mode a string indicating the attach mode.
	* @return ByteBuffer a direct allocated byte buffer
	* @throws IllegalArgumentException The lvmid or mode was invalid.
	* @throws IOException An I/O error occurred while trying to acquire
	* the instrumentation buffer.
	* @throws OutOfMemoryError The instrumentation buffer could not be mapped
	* into the virtual machine's address space.
	* @see java.nio.ByteBuffer
	*/
	public ByteBuffer attach(String user, int lvmid, String mode)
	throws IllegalArgumentException, IOException
	{
	if (mode.compareTo("r") == 0) {
	return attachImpl(user, lvmid, PERF_MODE_RO);
	}
	else if (mode.compareTo("rw") == 0) {
	return attachImpl(user, lvmid, PERF_MODE_RW);
	}
	else {
	throw new IllegalArgumentException("unknown mode");
	}
	}

	/**
	* Call the implementation specific attach method.
	* <p>
	* This method calls into the Java virtual machine to perform the platform
	* specific attach method. Buffers returned from this method are
	* internally managed as <code>PhantomRefereces</code> to provide for
	* guaranteed, secure release of the native resources.
	*
	* @param user A <code>String</code> object containing the
	* name of the user that owns the target Java
	* virtual machine.
	* @param lvmid an integer that uniquely identifies the
	* target local Java virtual machine.
	* @param mode a string indicating the attach mode.
	* @return ByteBuffer a direct allocated byte buffer
	* @throws IllegalArgumentException The lvmid or mode was invalid.
	* @throws IOException An I/O error occurred while trying to acquire
	* the instrumentation buffer.
	* @throws OutOfMemoryError The instrumentation buffer could not be mapped
	* into the virtual machine's address space.
	*/
	private ByteBuffer attachImpl(String user, int lvmid, int mode)
	throws IllegalArgumentException, IOException
	{
	final ByteBuffer b = attach(user, lvmid, mode);

	if (lvmid == 0) {
	// The native instrumentation buffer for this Java virtual
	// machine is never unmapped.
	return b;
	}
	else {
	// This is an instrumentation buffer for another Java virtual
	// machine with native resources that need to be managed. We
	// create a duplicate of the native ByteBuffer and manage it
	// with a Cleaner object (PhantomReference). When the duplicate
	// becomes only phantomly reachable, the native resources will
	// be released.

	final ByteBuffer dup = b.duplicate();
	Cleaner.create(dup, new Runnable() {
	public void run() {
	try {
	instance.detach(b);
	}
	catch (Throwable th) {
	// avoid crashing the reference handler thread,
	// but provide for some diagnosability
	assert false : th.toString();
	}
	}
	});
	return dup;
	}
	}

	/**
	* Native method to perform the implementation specific attach mechanism.
	* <p>
	* The implementation of this method may return distinct or identical
	* <code>ByteBuffer</code> objects for two distinct calls requesting
	* attachment to the same Java virtual machine.
	* <p>
	* For the Sun HotSpot JVM, two distinct calls to attach to the same
	* target Java virtual machine will result in two distinct ByteBuffer
	* objects returned by this method. This may change in a future release.
	*
	* @param user A <code>String</code> object containing the
	* name of the user that owns the target Java
	* virtual machine.
	* @param lvmid an integer that uniquely identifies the
	* target local Java virtual machine.
	* @param mode a string indicating the attach mode.
	* @return ByteBuffer a direct allocated byte buffer
	* @throws IllegalArgumentException The lvmid or mode was invalid.
	* @throws IOException An I/O error occurred while trying to acquire
	* the instrumentation buffer.
	* @throws OutOfMemoryError The instrumentation buffer could not be mapped
	* into the virtual machine's address space.
	*/
	private native ByteBuffer attach(String user, int lvmid, int mode)
	throws IllegalArgumentException, IOException;

	/**
	* Native method to perform the implementation specific detach mechanism.
	* <p>
	* If this method is passed a <code>ByteBuffer</code> object that is
	* not created by the <code>attach</code> method, then the results of
	* this method are undefined, with unpredictable and potentially damaging
	* effects to the Java virtual machine. To prevent accidental or malicious
	* use of this method, all native ByteBuffer created by the <code>
	* attach</code> method are managed internally as PhantomReferences
	* and resources are freed by the system.
	* <p>
	* If this method is passed a <code>ByteBuffer</code> object created
	* by the <code>attach</code> method with a lvmid for the Java virtual
	* machine running this method (lvmid=0, for example), then the detach
	* request is silently ignored.
	*
	* @param ByteBuffer A direct allocated byte buffer created by the
	* <code>attach</code> method.
	* @see java.nio.ByteBuffer
	* @see #attach
	*/
	private native void detach(ByteBuffer bb);

	/**
	* Create a <code>long</code> scalar entry in the instrumentation buffer
	* with the given variability characteristic, units, and initial value.
	* <p>
	* Access to the instrument is provided through the returned <code>
	* ByteBuffer</code> object. Typically, this object should be wrapped
	* with <code>LongBuffer</code> view object.
	*
	* @param variability the variability characteristic for this entry.
	* @param units the units for this entry.
	* @param name the name of this entry.
	* @param value the initial value for this entry.
	* @return ByteBuffer a direct allocated ByteBuffer object that
	* allows write access to a native memory location
	* containing a <code>long</code> value.
	*
	* see sun.misc.perf.Variability
	* see sun.misc.perf.Units
	* @see java.nio.ByteBuffer
	*/
	public native ByteBuffer createLong(String name, int variability,
	int units, long value);

	/**
	* Create a <code>String</code> entry in the instrumentation buffer with
	* the given variability characteristic, units, and initial value.
	* <p>
	* The maximum length of the <code>String</code> stored in this string
	* instrument is given in by <code>maxLength</code> parameter. Updates
	* to this instrument with <code>String</code> values with lengths greater
	* than <code>maxLength</code> will be truncated to <code>maxLength</code>.
	* The truncated value will be terminated by a null character.
	* <p>
	* The underlying implementation may further limit the length of the
	* value, but will continue to preserve the null terminator.
	* <p>
	* Access to the instrument is provided through the returned <code>
	* ByteBuffer</code> object.
	*
	* @param variability the variability characteristic for this entry.
	* @param units the units for this entry.
	* @param name the name of this entry.
	* @param value the initial value for this entry.
	* @param maxLength the maximum string length for this string
	* instrument.
	* @return ByteBuffer a direct allocated ByteBuffer that allows
	* write access to a native memory location
	* containing a <code>long</code> value.
	*
	* see sun.misc.perf.Variability
	* see sun.misc.perf.Units
	* @see java.nio.ByteBuffer
	*/
	public ByteBuffer createString(String name, int variability,
	int units, String value, int maxLength)
	{
	byte[] v = getBytes(value);
	byte[] v1 = new byte[v.length+1];
	System.arraycopy(v, 0, v1, 0, v.length);
	v1[v.length] = '\0';
	return createByteArray(name, variability, units, v1, Math.max(v1.length, maxLength));
	}

	/**
	* Create a <code>String</code> entry in the instrumentation buffer with
	* the given variability characteristic, units, and initial value.
	* <p>
	* The maximum length of the <code>String</code> stored in this string
	* instrument is implied by the length of the <code>value</code> parameter.
	* Subsequent updates to the value of this instrument will be truncated
	* to this implied maximum length. The truncated value will be terminated
	* by a null character.
	* <p>
	* The underlying implementation may further limit the length of the
	* initial or subsequent value, but will continue to preserve the null
	* terminator.
	* <p>
	* Access to the instrument is provided through the returned <code>
	* ByteBuffer</code> object.
	*
	* @param variability the variability characteristic for this entry.
	* @param units the units for this entry.
	* @param name the name of this entry.
	* @param value the initial value for this entry.
	* @return ByteBuffer a direct allocated ByteBuffer that allows
	* write access to a native memory location
	* containing a <code>long</code> value.
	*
	* see sun.misc.perf.Variability
	* see sun.misc.perf.Units
	* @see java.nio.ByteBuffer
	*/
	public ByteBuffer createString(String name, int variability,
	int units, String value)
	{
	byte[] v = getBytes(value);
	byte[] v1 = new byte[v.length+1];
	System.arraycopy(v, 0, v1, 0, v.length);
	v1[v.length] = '\0';
	return createByteArray(name, variability, units, v1, v1.length);
	}

	/**
	* Create a <code>byte</code> vector entry in the instrumentation buffer
	* with the given variability characteristic, units, and initial value.
	* <p>
	* The <code>maxLength</code> parameter limits the size of the byte
	* array instrument such that the initial or subsequent updates beyond
	* this length are silently ignored. No special handling of truncated
	* updates is provided.
	* <p>
	* The underlying implementation may further limit the length of the
	* length of the initial or subsequent value.
	* <p>
	* Access to the instrument is provided through the returned <code>
	* ByteBuffer</code> object.
	*
	* @param variability the variability characteristic for this entry.
	* @param units the units for this entry.
	* @param name the name of this entry.
	* @param value the initial value for this entry.
	* @param maxLength the maximum length of this byte array.
	* @return ByteBuffer a direct allocated byte buffer that allows
	* write access to a native memory location
	* containing a <code>long</code> value.
	*
	* see sun.misc.perf.Variability
	* see sun.misc.perf.Units
	* @see java.nio.ByteBuffer
	*/
	public native ByteBuffer createByteArray(String name, int variability,
	int units, byte[] value,
	int maxLength);


	/**
	* convert string to an array of UTF-8 bytes
	*/
	private static byte[] getBytes(String s)
	{
	byte[] bytes = null;

	try {
	bytes = s.getBytes("UTF-8");
	}
	catch (UnsupportedEncodingException e) {
	// ignore, UTF-8 encoding is always known
	}

	return bytes;
	}

	/**
	* Return the value of the High Resolution Counter.
	*
	* The High Resolution Counter returns the number of ticks since
	* since the start of the Java virtual machine. The resolution of
	* the counter is machine dependent and can be determined from the
	* value return by the {@link #highResFrequency} method.
	*
	* @return the number of ticks of machine dependent resolution since
	* the start of the Java virtual machine.
	*
	* @see #highResFrequency
	* @see java.lang.System#currentTimeMillis()
	*/
	public native long highResCounter();

	/**
	* Returns the frequency of the High Resolution Counter, in ticks per
	* second.
	*
	* This value can be used to convert the value of the High Resolution
	* Counter, as returned from a call to the {@link #highResCounter} method,
	* into the number of seconds since the start of the Java virtual machine.
	*
	* @return the frequency of the High Resolution Counter.
	* @see #highResCounter
	*/
	public native long highResFrequency();

	private static native void registerNatives();

	static {
	registerNatives();
	instance = new Perf();
	}
	}

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