JDK8/Java8源码在线阅读

/*
 * Copyright (c) 2003, 2012, 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.management;

import java.lang.management.GarbageCollectorMXBean;
import java.lang.management.MemoryUsage;
import javax.management.openmbean.OpenType;
import javax.management.openmbean.SimpleType;
import javax.management.openmbean.TabularType;
import javax.management.openmbean.TabularData;
import javax.management.openmbean.TabularDataSupport;
import javax.management.openmbean.CompositeType;
import javax.management.openmbean.CompositeData;
import javax.management.openmbean.CompositeDataSupport;
import javax.management.openmbean.OpenDataException;
import com.sun.management.GcInfo;

/**
 * Helper class to build composite data.
 */
public class GcInfoBuilder {
    private final GarbageCollectorMXBean gc;
    private final String[] poolNames;
    private String[] allItemNames;

    // GC-specific composite type:
    // Each GarbageCollectorMXBean may have different GC-specific attributes
    // the CompositeType for the GcInfo could be different.
    private CompositeType gcInfoCompositeType;

    // GC-specific items
    private final int gcExtItemCount;
    private final String[] gcExtItemNames;
    private final String[] gcExtItemDescs;
    private final char[] gcExtItemTypes;

    GcInfoBuilder(GarbageCollectorMXBean gc, String[] poolNames) {
        this.gc = gc;
        this.poolNames = poolNames;
        this.gcExtItemCount = getNumGcExtAttributes(gc);
        this.gcExtItemNames = new String[gcExtItemCount];
        this.gcExtItemDescs = new String[gcExtItemCount];
        this.gcExtItemTypes = new char[gcExtItemCount];

        // Fill the information about extension attributes
        fillGcAttributeInfo(gc, gcExtItemCount, gcExtItemNames,
                            gcExtItemTypes, gcExtItemDescs);

        // lazily build the CompositeType for the GcInfo
        // including the GC-specific extension attributes
        this.gcInfoCompositeType = null;
    }

    GcInfo getLastGcInfo() {
        MemoryUsage[] usageBeforeGC = new MemoryUsage[poolNames.length];
        MemoryUsage[] usageAfterGC = new MemoryUsage[poolNames.length];
        Object[] values = new Object[gcExtItemCount];

        return getLastGcInfo0(gc, gcExtItemCount, values, gcExtItemTypes,
                              usageBeforeGC, usageAfterGC);
    }

    public String[] getPoolNames() {
        return poolNames;
    }

    int getGcExtItemCount() {
        return gcExtItemCount;
    }

    // Returns the CompositeType for the GcInfo including
    // the extension attributes
    synchronized CompositeType getGcInfoCompositeType() {
        if (gcInfoCompositeType != null)
            return gcInfoCompositeType;

        // First, fill with the attributes in the GcInfo
        String[] gcInfoItemNames = GcInfoCompositeData.getBaseGcInfoItemNames();
        OpenType[] gcInfoItemTypes = GcInfoCompositeData.getBaseGcInfoItemTypes();
        int numGcInfoItems = gcInfoItemNames.length;

        int itemCount = numGcInfoItems + gcExtItemCount;
        allItemNames = new String[itemCount];
        String[] allItemDescs = new String[itemCount];
        OpenType<?>[] allItemTypes = new OpenType<?>[itemCount];

        System.arraycopy(gcInfoItemNames, 0, allItemNames, 0, numGcInfoItems);
        System.arraycopy(gcInfoItemNames, 0, allItemDescs, 0, numGcInfoItems);
        System.arraycopy(gcInfoItemTypes, 0, allItemTypes, 0, numGcInfoItems);

        // Then fill with the extension GC-specific attributes, if any.
        if (gcExtItemCount > 0) {
            fillGcAttributeInfo(gc, gcExtItemCount, gcExtItemNames,
                                gcExtItemTypes, gcExtItemDescs);
            System.arraycopy(gcExtItemNames, 0, allItemNames,
                             numGcInfoItems, gcExtItemCount);
            System.arraycopy(gcExtItemDescs, 0, allItemDescs,
                             numGcInfoItems, gcExtItemCount);
            for (int i = numGcInfoItems, j = 0; j < gcExtItemCount; i++, j++) {
                switch (gcExtItemTypes[j]) {
                    case 'Z':
                        allItemTypes[i] = SimpleType.BOOLEAN;
                        break;
                    case 'B':
                        allItemTypes[i] = SimpleType.BYTE;
                        break;
                    case 'C':
                        allItemTypes[i] = SimpleType.CHARACTER;
                        break;
                    case 'S':
                        allItemTypes[i] = SimpleType.SHORT;
                        break;
                    case 'I':
                        allItemTypes[i] = SimpleType.INTEGER;
                        break;
                    case 'J':
                        allItemTypes[i] = SimpleType.LONG;
                        break;
                    case 'F':
                        allItemTypes[i] = SimpleType.FLOAT;
                        break;
                    case 'D':
                        allItemTypes[i] = SimpleType.DOUBLE;
                        break;
                    default:
                        throw new AssertionError(
                            "Unsupported type [" + gcExtItemTypes[i] + "]");
                }
            }
        }

        CompositeType gict = null;
        try {
            final String typeName =
                "sun.management." + gc.getName() + ".GcInfoCompositeType";

            gict = new CompositeType(typeName,
                                     "CompositeType for GC info for " +
                                         gc.getName(),
                                     allItemNames,
                                     allItemDescs,
                                     allItemTypes);
        } catch (OpenDataException e) {
            // shouldn't reach here
            throw Util.newException(e);
        }
        gcInfoCompositeType = gict;

        return gcInfoCompositeType;
    }

    synchronized String[] getItemNames() {
        if (allItemNames == null) {
            // initialize when forming the composite type
            getGcInfoCompositeType();
        }
        return allItemNames;
    }

    // Retrieve information about extension attributes
    private native int getNumGcExtAttributes(GarbageCollectorMXBean gc);
    private native void fillGcAttributeInfo(GarbageCollectorMXBean gc,
                                            int numAttributes,
                                            String[] attributeNames,

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