/* * Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */  /* * The Original Code is HAT. The Initial Developer of the * Original Code is Bill Foote, with contributions from others * at JavaSoft/Sun. */ package com.sun.tools.hat.internal.parser; import java.io.IOException;import java.io.RandomAccessFile;import java.nio.MappedByteBuffer;import java.nio.channels.FileChannel; /** * Implementation of ReadBuffer using mapped file buffer * * @author A. Sundararajan */class MappedReadBuffer implements ReadBuffer {    private MappedByteBuffer buf;     MappedReadBuffer(MappedByteBuffer buf) {        this.buf = buf;    }     // factory method to create correct ReadBuffer for a given file    static ReadBuffer create(RandomAccessFile file) throws IOException {        FileChannel ch = file.getChannel();        long size = ch.size();        // if file size is more than 2 GB and when file mapping is        // configured (default), use mapped file reader        if (canUseFileMap() && (size <= Integer.MAX_VALUE)) {            MappedByteBuffer buf;            try {                buf = ch.map(FileChannel.MapMode.READ_ONLY, 0, size);                ch.close();                return new MappedReadBuffer(buf);            } catch (IOException exp) {                exp.printStackTrace();                System.err.println("File mapping failed, will use direct read");                // fall through            }        } // else fall through        return new FileReadBuffer(file);    }     private static boolean canUseFileMap() {        // set jhat.disableFileMap to any value other than "false"        // to disable file mapping        String prop = System.getProperty("jhat.disableFileMap");        return prop == null || prop.equals("false");    }     private void seek(long pos) throws IOException {        assert pos <= Integer.MAX_VALUE :  "position overflow";        buf.position((int)pos);    }     public synchronized void get(long pos, byte[] res) throws IOException {        seek(pos);        buf.get(res);    }     public synchronized char getChar(long pos) throws IOException {        seek(pos);        return buf.getChar();    }     public synchronized byte getByte(long pos) throws IOException {        seek(pos);        return buf.get();    }     public synchronized short getShort(long pos) throws IOException {        seek(pos);        return buf.getShort();    }     public synchronized int getInt(long pos) throws IOException {        seek(pos);        return buf.getInt();    }     public synchronized long getLong(long pos) throws IOException {        seek(pos);        return buf.getLong();    }}