Java example source code file (PerfDataEntry.java)

This example Java source code file (PerfDataEntry.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

data_type_size, data_unit_size, data_var_size, flags, flags_size, instrumentationexception, invalid, name_offset, name_offset_size, nio, perfdataentry, sizeof_byte, sizeof_int, string, vector_length_size

The PerfDataEntry.java Java example source code

/*
 * Copyright (c) 2003, 2011, 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.counter.perf;

import sun.management.counter.*;
import java.nio.*;
import java.io.UnsupportedEncodingException;

class PerfDataEntry {
    private class EntryFieldOffset {
        private final static int SIZEOF_BYTE = 1;
        private final static int SIZEOF_INT  = 4;
        private final static int SIZEOF_LONG = 8;

        private final static int ENTRY_LENGTH_SIZE    = SIZEOF_INT;
        private final static int NAME_OFFSET_SIZE     = SIZEOF_INT;
        private final static int VECTOR_LENGTH_SIZE   = SIZEOF_INT;
        private final static int DATA_TYPE_SIZE       = SIZEOF_BYTE;
        private final static int FLAGS_SIZE           = SIZEOF_BYTE;
        private final static int DATA_UNIT_SIZE       = SIZEOF_BYTE;
        private final static int DATA_VAR_SIZE        = SIZEOF_BYTE;
        private final static int DATA_OFFSET_SIZE     = SIZEOF_INT;

        final static int ENTRY_LENGTH  = 0;
        final static int NAME_OFFSET   = ENTRY_LENGTH + ENTRY_LENGTH_SIZE;
        final static int VECTOR_LENGTH = NAME_OFFSET + NAME_OFFSET_SIZE;;
        final static int DATA_TYPE     = VECTOR_LENGTH + VECTOR_LENGTH_SIZE;
        final static int FLAGS         = DATA_TYPE + DATA_TYPE_SIZE;
        final static int DATA_UNIT     = FLAGS + FLAGS_SIZE;
        final static int DATA_VAR      = DATA_UNIT + DATA_UNIT_SIZE;
        final static int DATA_OFFSET   = DATA_VAR + DATA_VAR_SIZE;
    }

    private String       name;
    private int          entryStart;
    private int          entryLength;
    private int          vectorLength;
    private PerfDataType dataType;
    private int          flags;
    private Units        unit;
    private Variability  variability;
    private int          dataOffset;
    private int          dataSize;
    private ByteBuffer   data;

    PerfDataEntry(ByteBuffer b) {
        entryStart = b.position();
        entryLength = b.getInt();

        // check for valid entry length
        if (entryLength <= 0 || entryLength > b.limit()) {
            throw new InstrumentationException("Invalid entry length: " +
                                               " entryLength = " + entryLength);
        }
        // check if last entry occurs before the eof.
        if ((entryStart + entryLength) > b.limit()) {
            throw new InstrumentationException("Entry extends beyond end of buffer: " +
                                               " entryStart = " + entryStart +
                                               " entryLength = " + entryLength +
                                               " buffer limit = " + b.limit());
        }

        b.position(entryStart + EntryFieldOffset.NAME_OFFSET);
        int nameOffset = b.getInt();

        if ((entryStart + nameOffset) > b.limit()) {
            throw new InstrumentationException("Invalid name offset: " +
                                               " entryStart = " + entryStart +
                                               " nameOffset = " + nameOffset +
                                               " buffer limit = " + b.limit());
        }


        b.position(entryStart + EntryFieldOffset.VECTOR_LENGTH);
        vectorLength = b.getInt();

        b.position(entryStart + EntryFieldOffset.DATA_TYPE);
        dataType = PerfDataType.toPerfDataType(b.get());

        b.position(entryStart + EntryFieldOffset.FLAGS);
        flags = b.get();

        b.position(entryStart + EntryFieldOffset.DATA_UNIT);
        unit = Units.toUnits(b.get());

        b.position(entryStart + EntryFieldOffset.DATA_VAR);
        variability = Variability.toVariability(b.get());

        b.position(entryStart + EntryFieldOffset.DATA_OFFSET);
        dataOffset = b.getInt();

        // read in the perfData item name, casting bytes to chars. skip the
        // null terminator
        b.position(entryStart + nameOffset);
        // calculate the length of the name
        int nameLength = 0;
        byte c;
        for (; (c = b.get()) != (byte)0; nameLength++);

        byte[] symbolBytes = new byte[nameLength];
        b.position(entryStart + nameOffset);
        for (int i = 0; i < nameLength; i++) {
            symbolBytes[i] = b.get();
        }

        // convert name into a String
        try {
            name = new String(symbolBytes, "UTF-8");
        }
        catch (UnsupportedEncodingException e) {
            // should not reach here
            // "UTF-8" is always a known encoding
            throw new InternalError(e.getMessage(), e);
        }

        if (variability == Variability.INVALID) {
            throw new InstrumentationException("Invalid variability attribute:" +
                                               " name = " + name);
        }
        if (unit == Units.INVALID) {
            throw new InstrumentationException("Invalid units attribute: " +
                                               " name = " + name);
        }

        if (vectorLength > 0) {
            dataSize = vectorLength * dataType.size();
        } else {
            dataSize = dataType.size();
        }

        // check if data beyond the eof.
        if ((entryStart + dataOffset + dataSize) > b.limit()) {
            throw new InstrumentationException("Data extends beyond end of buffer: " +
                                               " entryStart = " + entryStart +
                                               " dataOffset = " + dataOffset+
                                               " dataSize = " + dataSize +
                                               " buffer limit = " + b.limit());
        }
        // Construct a ByteBuffer for the data
        b.position(entryStart + dataOffset);
        data = b.slice();
        data.order(b.order());
        data.limit(dataSize);
    }


    public int size() {
        return entryLength;
    }

    public String name() {
        return name;
    }

    public PerfDataType type() {
        return dataType;
    }

    public Units units() {
        return unit;
    }

    public int flags() {
        return flags;
    }

    /**
     * Returns the number of elements in the data.
     */
    public int vectorLength() {
        return vectorLength;
    }

    public Variability variability() {
        return variability;
    }

    public ByteBuffer byteData() {
        data.position(0);
        assert data.remaining() == vectorLength();
        return data.duplicate();
    }

    public LongBuffer longData() {
        LongBuffer lb = data.asLongBuffer();
        return lb;
    }
}