/*

 * 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.model;

import java.io.File;

import java.io.FileInputStream;

import java.io.InputStreamReader;

import java.io.Reader;

import java.io.BufferedReader;

import java.io.IOException;

import java.util.Hashtable;

/**

 * This represents a set of data members that should be excluded from the

 * reachable objects query.

 * This is useful to exclude observers from the

 * transitive closure of objects reachable from a given object, allowing

 * some kind of real determination of the "size" of that object.

 *

 * @author      Bill Foote

 */

public class ReachableExcludesImpl implements ReachableExcludes {

    private File excludesFile;

    private long lastModified;

    private Hashtable methods;  // Hashtable<String, String>, used as a bag

    /**

     * Create a new ReachableExcludesImpl over the given file.  The file will be

     * re-read whenever the timestamp changes.

     */

    public ReachableExcludesImpl(File excludesFile) {

        this.excludesFile = excludesFile;

        readFile();

    }

    private void readFileIfNeeded() {

        if (excludesFile.lastModified() != lastModified) {

            synchronized(this) {

                if (excludesFile.lastModified() != lastModified) {

                    readFile();

                }

            }

        }

    }

    private void readFile() {

        long lm = excludesFile.lastModified();

        Hashtable<String, String> m = new Hashtable<String, String>();

        try {

            BufferedReader r = new BufferedReader(new InputStreamReader(

                                    new FileInputStream(excludesFile)));

            String method;

            while ((method = r.readLine()) != null) {

                m.put(method, method);

            }

            lastModified = lm;

            methods = m;        // We want this to be atomic

        } catch (IOException ex) {

            System.out.println("Error reading " + excludesFile + ":  " + ex);

        }

    }

    /**

     * @return true iff the given field is on the histlist of excluded

     *          fields.

     */

    public boolean isExcluded(String fieldName) {

        readFileIfNeeded();

        return methods.get(fieldName) != null;

    }

}