1 /*

     2  * Copyright (c) 1997, 2008, 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 

    27 /*

    28  * The Original Code is HAT. The Initial Developer of the

    29  * Original Code is Bill Foote, with contributions from others

    30  * at JavaSoft/Sun.

    31  */

    32 

    33 package com.sun.tools.hat.internal.parser;

    34 

    35 import java.io.IOException;

    36 import java.io.RandomAccessFile;

    37 import java.nio.MappedByteBuffer;

    38 import java.nio.channels.FileChannel;

    39 

    40 /**

    41  * Implementation of ReadBuffer using mapped file buffer

    42  *

    43  * @author A. Sundararajan

    44  */

    45 class MappedReadBuffer implements ReadBuffer {

    46     private MappedByteBuffer buf;

    47 

    48     MappedReadBuffer(MappedByteBuffer buf) {

    49         this.buf = buf;

    50     }

    51 

    52     // factory method to create correct ReadBuffer for a given file

    53     static ReadBuffer create(RandomAccessFile file) throws IOException {

    54         FileChannel ch = file.getChannel();

    55         long size = ch.size();

    56         // if file size is more than 2 GB and when file mapping is

    57         // configured (default), use mapped file reader

    58         if (canUseFileMap() && (size <= Integer.MAX_VALUE)) {

    59             MappedByteBuffer buf;

    60             try {

    61                 buf = ch.map(FileChannel.MapMode.READ_ONLY, 0, size);

    62                 ch.close();

    63                 return new MappedReadBuffer(buf);

    64             } catch (IOException exp) {

    65                 exp.printStackTrace();

    66                 System.err.println("File mapping failed, will use direct read");

    67                 // fall through

    68             }

    69         } // else fall through

    70         return new FileReadBuffer(file);

    71     }

    72 

    73     private static boolean canUseFileMap() {

    74         // set jhat.disableFileMap to any value other than "false"

    75         // to disable file mapping

    76         String prop = System.getProperty("jhat.disableFileMap");

    77         return prop == null || prop.equals("false");

    78     }

    79 

    80     private void seek(long pos) throws IOException {

    81         assert pos <= Integer.MAX_VALUE :  "position overflow";

    82         buf.position((int)pos);

    83     }

    84 

    85     public synchronized void get(long pos, byte[] res) throws IOException {

    86         seek(pos);

    87         buf.get(res);

    88     }

    89 

    90     public synchronized char getChar(long pos) throws IOException {

    91         seek(pos);

    92         return buf.getChar();

    93     }

    94 

    95     public synchronized byte getByte(long pos) throws IOException {

    96         seek(pos);

    97         return buf.get();

    98     }

    99 

   100     public synchronized short getShort(long pos) throws IOException {

   101         seek(pos);

   102         return buf.getShort();

   103     }

   104 

   105     public synchronized int getInt(long pos) throws IOException {

   106         seek(pos);

   107         return buf.getInt();

   108     }

   109 

   110     public synchronized long getLong(long pos) throws IOException {

   111         seek(pos);

   112         return buf.getLong();

   113     }

   114 }