1 /*
   2  * Copyright (c) 1997, 2015, 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 jdk.test.lib.hprof.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     private RandomAccessFile file;
  48 
  49     MappedReadBuffer(RandomAccessFile file, MappedByteBuffer buf) {
  50         this.file = file;
  51         this.buf = buf;
  52     }
  53 
  54     /**
  55      * Factory method to create correct ReadBuffer for a given file.
  56      *
  57      * The initial purpose of this method was to choose how to read hprof file for parsing
  58      * depending on the size of the file and the system property 'jhat.disableFileMap':
  59      * "If file size is more than 2 GB and when file mapping is configured (default),
  60      * use mapped file reader".
  61      *
  62      * However, it has been discovered a problem with this approach.
  63      * Creating java.nio.MappedByteBuffer from inside the test leads to hprof file
  64      * is locked on Windows until test process dies since there is no good way to
  65      * release this resource.
  66      *
  67      * java.nio.MappedByteBuffer will be used only if 'jhat.enableFileMap' is set to true.
  68      * Per default 'jhat.enableFileMap' is not set.
  69      */
  70     static ReadBuffer create(RandomAccessFile file) throws IOException {
  71         if (canUseFileMap()) {
  72             MappedByteBuffer buf;
  73             try {
  74                 FileChannel ch = file.getChannel();
  75                 long size = ch.size();
  76                 buf = ch.map(FileChannel.MapMode.READ_ONLY, 0, size);
  77                 ch.close();
  78                 return new MappedReadBuffer(file, buf);
  79             } catch (IOException exp) {
  80                 exp.printStackTrace();
  81                 System.err.println("File mapping failed, will use direct read");
  82                 // fall through
  83             }
  84         } // else fall through
  85         return new FileReadBuffer(file);
  86     }
  87 
  88     /**
  89      * Set system property 'jhat.enableFileMap' to 'true' to enable file mapping.
  90      */
  91     private static boolean canUseFileMap() {
  92         String prop = System.getProperty("jhat.enableFileMap");
  93         return prop != null && prop.equals("true");
  94     }
  95 
  96     private void seek(long pos) throws IOException {
  97         assert pos <= Integer.MAX_VALUE :  "position overflow";
  98         buf.position((int)pos);
  99     }
 100 
 101     public synchronized void get(long pos, byte[] res) throws IOException {
 102         seek(pos);
 103         buf.get(res);
 104     }
 105 
 106     public synchronized char getChar(long pos) throws IOException {
 107         seek(pos);
 108         return buf.getChar();
 109     }
 110 
 111     public synchronized byte getByte(long pos) throws IOException {
 112         seek(pos);
 113         return buf.get();
 114     }
 115 
 116     public synchronized short getShort(long pos) throws IOException {
 117         seek(pos);
 118         return buf.getShort();
 119     }
 120 
 121     public synchronized int getInt(long pos) throws IOException {
 122         seek(pos);
 123         return buf.getInt();
 124     }
 125 
 126     public synchronized long getLong(long pos) throws IOException {
 127         seek(pos);
 128         return buf.getLong();
 129     }
 130 
 131     @Override
 132     public void close() throws Exception {
 133         file.close();
 134     }
 135 
 136 }