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 
  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 }