1 /*

     2  * Copyright (c) 2004, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package sun.jvmstat.perfdata.monitor;

    27 

    28 import sun.jvmstat.monitor.*;

    29 import java.nio.ByteOrder;

    30 import java.nio.ByteBuffer;

    31 import java.nio.IntBuffer;

    32 

    33 /**

    34  * Abstraction representing the HotSpot PerfData instrumentation buffer

    35  * header. This class represents only the fixed portion of the header.

    36  * Version specific classes represent the portion of the header that

    37  * may change from release to release.

    38  * <p>

    39  * The PerfDataBufferProlog class supports parsing of the following

    40  * C structure:

    41  * <pre>

    42  * typedef struct {

    43  *   jint magic;             // magic number - 0xcafec0c0

    44  *   jbyte byte_order;       // byte order of the buffer

    45  *   jbyte major_version;    // major and minor version numbers

    46  *   jbyte minor_version;

    47  *   jbyte reserved_byte1;   // reserved - see concrete implementations for

    48  *                           // possible definition.

    49  *   ...                     // remainder is handled by the subclasses.

    50  * } PerfDataPrologue

    51  * </pre>

    52  *

    53  * @author Brian Doherty

    54  * @since 1.5

    55  */

    56 public abstract class AbstractPerfDataBufferPrologue {

    57 

    58     protected ByteBuffer byteBuffer;

    59 

    60     /*

    61      * the following constants must match the field offsets and sizes

    62      * in the PerfDataPrologue structure in perfMemory.hpp

    63      */

    64     final static int PERFDATA_PROLOG_OFFSET=0;

    65     final static int PERFDATA_PROLOG_MAGIC_OFFSET=0;

    66     final static int PERFDATA_PROLOG_BYTEORDER_OFFSET=4;

    67     final static int PERFDATA_PROLOG_BYTEORDER_SIZE=1;         // sizeof(byte)

    68     final static int PERFDATA_PROLOG_MAJOR_OFFSET=5;

    69     final static int PERFDATA_PROLOG_MAJOR_SIZE=1;             // sizeof(byte)

    70     final static int PERFDATA_PROLOG_MINOR_OFFSET=6;

    71     final static int PERFDATA_PROLOG_MINOR_SIZE=1;             // sizeof(byte)

    72     final static int PERFDATA_PROLOG_RESERVEDB1_OFFSET=7;

    73     final static int PERFDATA_PROLOG_RESERVEDB1_SIZE=1;        // sizeof(byte)

    74 

    75     final static int PERFDATA_PROLOG_SIZE=8;   // sizeof(struct PerfDataProlog)

    76 

    77     // these constants should match their #define counterparts in perfMemory.hpp

    78     final static byte PERFDATA_BIG_ENDIAN=0;

    79     final static byte PERFDATA_LITTLE_ENDIAN=1;

    80     final static int  PERFDATA_MAGIC = 0xcafec0c0;

    81 

    82     // names for counters that expose the prolog fields

    83     public final static String PERFDATA_MAJOR_NAME =

    84             "sun.perfdata.majorVersion";

    85     public final static String PERFDATA_MINOR_NAME =

    86             "sun.perfdata.minorVersion";

    87 

    88     /**

    89      * Construct a PerfDataBufferPrologue instance.

    90      *

    91      * @param byteBuffer buffer containing the instrumentation data

    92      */

    93     public AbstractPerfDataBufferPrologue(ByteBuffer byteBuffer)

    94            throws MonitorException  {

    95         this.byteBuffer = byteBuffer.duplicate();

    96 

    97         // the magic number is always stored in big-endian format

    98         if (getMagic() != PERFDATA_MAGIC) {

    99             throw new MonitorVersionException(

   100                     "Bad Magic: " + Integer.toHexString(getMagic()));

   101         }

   102 

   103         // set the byte order

   104         this.byteBuffer.order(getByteOrder());

   105     }

   106 

   107     /**

   108      * Get the magic number.

   109      *

   110      * @return int - the magic number

   111      */

   112     public int getMagic() {

   113         // the magic number is always stored in big-endian format

   114         ByteOrder order = byteBuffer.order();

   115         byteBuffer.order(ByteOrder.BIG_ENDIAN);

   116 

   117         // get the magic number

   118         byteBuffer.position(PERFDATA_PROLOG_MAGIC_OFFSET);

   119         int magic = byteBuffer.getInt();

   120 

   121         // restore the byte order

   122         byteBuffer.order(order);

   123         return magic;

   124     }

   125 

   126     /**

   127      * Get the byte order.

   128      *

   129      * @return int - the byte order of the instrumentation buffer

   130      */

   131     public ByteOrder getByteOrder() {

   132         // byte order field is byte order independent

   133         byteBuffer.position(PERFDATA_PROLOG_BYTEORDER_OFFSET);

   134 

   135         byte byte_order = byteBuffer.get();

   136 

   137         if (byte_order == PERFDATA_BIG_ENDIAN) {

   138             return ByteOrder.BIG_ENDIAN;

   139         } else {

   140             return ByteOrder.LITTLE_ENDIAN;

   141         }

   142     }

   143 

   144     /**

   145      * Get the major version.

   146      *

   147      * @return int - the major version

   148      */

   149     public int getMajorVersion() {

   150         // major version field is byte order independent

   151         byteBuffer.position(PERFDATA_PROLOG_MAJOR_OFFSET);

   152         return (int)byteBuffer.get();

   153     }

   154 

   155     /**

   156      * Get the minor version.

   157      *

   158      * @return int - the minor version

   159      */

   160     public int getMinorVersion() {

   161         // minor version field is byte order independent

   162         byteBuffer.position(PERFDATA_PROLOG_MINOR_OFFSET);

   163         return (int)byteBuffer.get();

   164     }

   165 

   166     /**

   167      * Get the accessible flag. If supported, it indicates that the shared

   168      * memory region is sufficiently initialized for client acccess.

   169      *

   170      * @return boolean - the initialized status

   171      * @see #supportsAccessible()

   172      */

   173     public abstract boolean isAccessible();

   174 

   175     /**

   176      * Test if the accessible flag is supported by this version of

   177      * the PerfDataBufferPrologue. Although not an abstract method, this

   178      * method should be overridden by version specific subclasses.

   179      *

   180      * @return boolean - the initialized flag support status.

   181      * @see #isAccessible()

   182      */

   183     public abstract boolean supportsAccessible();

   184 

   185     /**

   186      * Get the size of the header portion of the instrumentation buffer.

   187      *

   188      * @return int - the size of the header

   189      */

   190     public int getSize() {

   191         return PERFDATA_PROLOG_SIZE;  // sizeof(struct PerfDataProlog)

   192     }

   193 

   194     /**

   195      * Return an IntBuffer that accesses the major version number.

   196      * This is used to create a Monitor object for this value.

   197      *

   198      * @return IntBuffer - a ByteBuffer that accesses the major version number

   199      *                     in the instrumentation buffer header.

   200      */

   201     public IntBuffer majorVersionBuffer() {

   202         int[] holder = new int[1];

   203         holder[0] = getMajorVersion();

   204         IntBuffer ib = IntBuffer.wrap(holder);

   205         ib.limit(1);

   206         return ib;

   207       }

   208 

   209     /**

   210      * Return an IntBuffer that accesses the minor version number.

   211      * This is used to create a Monitor object for this value.

   212      *

   213      * @return IntBuffer - a ByteBuffer that accesses the minor version number

   214      *                     in the instrumentation buffer header.

   215      */

   216     public IntBuffer minorVersionBuffer() {

   217         int[] holder = new int[1];

   218         holder[0] = getMinorVersion();

   219         IntBuffer ib = IntBuffer.wrap(holder);

   220         ib.limit(1);

   221         return ib;

   222     }

   223 

   224     /**

   225      * Get the magic number from the given byteBuffer.

   226      *

   227      * @return int - the magic number

   228      */

   229     public static int getMagic(ByteBuffer bb) {

   230         // save buffer state

   231         int position = bb.position();

   232         ByteOrder order = bb.order();

   233 

   234         // the magic number is always stored in big-endian format

   235         bb.order(ByteOrder.BIG_ENDIAN);

   236         bb.position(PERFDATA_PROLOG_MAGIC_OFFSET);

   237         int magic = bb.getInt();

   238 

   239         // restore buffer state.

   240         bb.order(order);

   241         bb.position(position);

   242 

   243         return magic;

   244     }

   245 

   246     /**

   247      * Get the major version number from the given ByteBuffer.

   248      *

   249      * @return int - the major version

   250      */

   251     public static int getMajorVersion(ByteBuffer bb) {

   252         // save buffer state

   253         int position = bb.position();

   254 

   255         bb.position(PERFDATA_PROLOG_MAJOR_OFFSET);

   256         int major = (int) bb.get();

   257 

   258         // restore buffer state.

   259         bb.position(position);

   260 

   261         return major;

   262     }

   263 

   264     /**

   265      * Get the minor version number from the given ByteBuffer.

   266      *

   267      * @return int - the minor version

   268      */

   269     public static int getMinorVersion(ByteBuffer bb) {

   270         // save buffer state

   271         int position = bb.position();

   272 

   273         bb.position(PERFDATA_PROLOG_MINOR_OFFSET);

   274         int minor = (int)bb.get();

   275 

   276         // restore buffer state.

   277         bb.position(position);

   278 

   279         return minor;

   280     }

   281 

   282     /**

   283      * Get the byte order for the given ByteBuffer.

   284      *

   285      * @return int - the byte order of the instrumentation buffer

   286      */

   287     public static ByteOrder getByteOrder(ByteBuffer bb) {

   288         // save buffer state

   289         int position = bb.position();

   290 

   291         bb.position(PERFDATA_PROLOG_BYTEORDER_OFFSET);

   292         ByteOrder order = (bb.get() == PERFDATA_BIG_ENDIAN)

   293                           ? ByteOrder.BIG_ENDIAN

   294                           : ByteOrder.LITTLE_ENDIAN;

   295 

   296         // restore buffer state.

   297         bb.position(position);

   298         return order;

   299     }

   300 }