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