MappedReadBuffer.java revision 2224:2a8815d86b93
1/* 2 * Copyright (c) 1997, 2016, 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 33package jdk.test.lib.hprof.parser; 34 35import java.io.IOException; 36import java.io.RandomAccessFile; 37import java.nio.MappedByteBuffer; 38import java.nio.channels.FileChannel; 39 40/** 41 * Implementation of ReadBuffer using mapped file buffer 42 * 43 * @author A. Sundararajan 44 */ 45class 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} 137