/* * Copyright (c) 2004, 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.jvmstat.perfdata.monitor; import sun.jvmstat.monitor.*; import java.nio.ByteOrder; import java.nio.ByteBuffer; import java.nio.IntBuffer; /** * Abstraction representing the HotSpot PerfData instrumentation buffer * header. This class represents only the fixed portion of the header. * Version specific classes represent the portion of the header that * may change from release to release. *

* The PerfDataBufferProlog class supports parsing of the following * C structure: *

 * typedef struct {
 *   jint magic;             // magic number - 0xcafec0c0
 *   jbyte byte_order;       // byte order of the buffer
 *   jbyte major_version;    // major and minor version numbers
 *   jbyte minor_version;
 *   jbyte reserved_byte1;   // reserved - see concrete implementations for
 *                           // possible definition.
 *   ...                     // remainder is handled by the subclasses.
 * } PerfDataPrologue
 * 
* * @author Brian Doherty * @since 1.5 */ public abstract class AbstractPerfDataBufferPrologue { protected ByteBuffer byteBuffer; /* * the following constants must match the field offsets and sizes * in the PerfDataPrologue structure in perfMemory.hpp */ final static int PERFDATA_PROLOG_OFFSET=0; final static int PERFDATA_PROLOG_MAGIC_OFFSET=0; final static int PERFDATA_PROLOG_BYTEORDER_OFFSET=4; final static int PERFDATA_PROLOG_BYTEORDER_SIZE=1; // sizeof(byte) final static int PERFDATA_PROLOG_MAJOR_OFFSET=5; final static int PERFDATA_PROLOG_MAJOR_SIZE=1; // sizeof(byte) final static int PERFDATA_PROLOG_MINOR_OFFSET=6; final static int PERFDATA_PROLOG_MINOR_SIZE=1; // sizeof(byte) final static int PERFDATA_PROLOG_RESERVEDB1_OFFSET=7; final static int PERFDATA_PROLOG_RESERVEDB1_SIZE=1; // sizeof(byte) final static int PERFDATA_PROLOG_SIZE=8; // sizeof(struct PerfDataProlog) // these constants should match their #define counterparts in perfMemory.hpp final static byte PERFDATA_BIG_ENDIAN=0; final static byte PERFDATA_LITTLE_ENDIAN=1; final static int PERFDATA_MAGIC = 0xcafec0c0; // names for counters that expose the prolog fields public final static String PERFDATA_MAJOR_NAME = "sun.perfdata.majorVersion"; public final static String PERFDATA_MINOR_NAME = "sun.perfdata.minorVersion"; /** * Construct a PerfDataBufferPrologue instance. * * @param byteBuffer buffer containing the instrumentation data */ public AbstractPerfDataBufferPrologue(ByteBuffer byteBuffer) throws MonitorException { this.byteBuffer = byteBuffer.duplicate(); // the magic number is always stored in big-endian format if (getMagic() != PERFDATA_MAGIC) { throw new MonitorVersionException( "Bad Magic: " + Integer.toHexString(getMagic())); } // set the byte order this.byteBuffer.order(getByteOrder()); } /** * Get the magic number. * * @return int - the magic number */ public int getMagic() { // the magic number is always stored in big-endian format ByteOrder order = byteBuffer.order(); byteBuffer.order(ByteOrder.BIG_ENDIAN); // get the magic number byteBuffer.position(PERFDATA_PROLOG_MAGIC_OFFSET); int magic = byteBuffer.getInt(); // restore the byte order byteBuffer.order(order); return magic; } /** * Get the byte order. * * @return int - the byte order of the instrumentation buffer */ public ByteOrder getByteOrder() { // byte order field is byte order independent byteBuffer.position(PERFDATA_PROLOG_BYTEORDER_OFFSET); byte byte_order = byteBuffer.get(); if (byte_order == PERFDATA_BIG_ENDIAN) { return ByteOrder.BIG_ENDIAN; } else { return ByteOrder.LITTLE_ENDIAN; } } /** * Get the major version. * * @return int - the major version */ public int getMajorVersion() { // major version field is byte order independent byteBuffer.position(PERFDATA_PROLOG_MAJOR_OFFSET); return (int)byteBuffer.get(); } /** * Get the minor version. * * @return int - the minor version */ public int getMinorVersion() { // minor version field is byte order independent byteBuffer.position(PERFDATA_PROLOG_MINOR_OFFSET); return (int)byteBuffer.get(); } /** * Get the accessible flag. If supported, it indicates that the shared * memory region is sufficiently initialized for client acccess. * * @return boolean - the initialized status * @see #supportsAccessible() */ public abstract boolean isAccessible(); /** * Test if the accessible flag is supported by this version of * the PerfDataBufferPrologue. Although not an abstract method, this * method should be overridden by version specific subclasses. * * @return boolean - the initialized flag support status. * @see #isAccessible() */ public abstract boolean supportsAccessible(); /** * Get the size of the header portion of the instrumentation buffer. * * @return int - the size of the header */ public int getSize() { return PERFDATA_PROLOG_SIZE; // sizeof(struct PerfDataProlog) } /** * Return an IntBuffer that accesses the major version number. * This is used to create a Monitor object for this value. * * @return IntBuffer - a ByteBuffer that accesses the major version number * in the instrumentation buffer header. */ public IntBuffer majorVersionBuffer() { int[] holder = new int[1]; holder[0] = getMajorVersion(); IntBuffer ib = IntBuffer.wrap(holder); ib.limit(1); return ib; } /** * Return an IntBuffer that accesses the minor version number. * This is used to create a Monitor object for this value. * * @return IntBuffer - a ByteBuffer that accesses the minor version number * in the instrumentation buffer header. */ public IntBuffer minorVersionBuffer() { int[] holder = new int[1]; holder[0] = getMinorVersion(); IntBuffer ib = IntBuffer.wrap(holder); ib.limit(1); return ib; } /** * Get the magic number from the given byteBuffer. * * @return int - the magic number */ public static int getMagic(ByteBuffer bb) { // save buffer state int position = bb.position(); ByteOrder order = bb.order(); // the magic number is always stored in big-endian format bb.order(ByteOrder.BIG_ENDIAN); bb.position(PERFDATA_PROLOG_MAGIC_OFFSET); int magic = bb.getInt(); // restore buffer state. bb.order(order); bb.position(position); return magic; } /** * Get the major version number from the given ByteBuffer. * * @return int - the major version */ public static int getMajorVersion(ByteBuffer bb) { // save buffer state int position = bb.position(); bb.position(PERFDATA_PROLOG_MAJOR_OFFSET); int major = (int) bb.get(); // restore buffer state. bb.position(position); return major; } /** * Get the minor version number from the given ByteBuffer. * * @return int - the minor version */ public static int getMinorVersion(ByteBuffer bb) { // save buffer state int position = bb.position(); bb.position(PERFDATA_PROLOG_MINOR_OFFSET); int minor = (int)bb.get(); // restore buffer state. bb.position(position); return minor; } /** * Get the byte order for the given ByteBuffer. * * @return int - the byte order of the instrumentation buffer */ public static ByteOrder getByteOrder(ByteBuffer bb) { // save buffer state int position = bb.position(); bb.position(PERFDATA_PROLOG_BYTEORDER_OFFSET); ByteOrder order = (bb.get() == PERFDATA_BIG_ENDIAN) ? ByteOrder.BIG_ENDIAN : ByteOrder.LITTLE_ENDIAN; // restore buffer state. bb.position(position); return order; } }