/*

 * Copyright (c) 2015, 2016, 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.

 */

package jdk.internal.jimage;

import java.io.IOException;

import java.io.UncheckedIOException;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.util.concurrent.ConcurrentHashMap;

import java.util.Map;

import java.util.Objects;

import java.util.function.Function;

/**

 * Factory to get ImageReader

 *

 * @implNote This class needs to maintain JDK 8 source compatibility.

 *

 * It is used internally in the JDK to implement jimage/jrtfs access,

 * but also compiled and delivered as part of the jrtfs.jar to support access

 * to the jimage file provided by the shipped JDK by tools running on JDK 8.

 */

public class ImageReaderFactory {

    private ImageReaderFactory() {}

    private static final String JAVA_HOME = System.getProperty("java.home");

    private static final Path BOOT_MODULES_JIMAGE =

        Paths.get(JAVA_HOME, "lib", "modules");

    private static final Map<Path, ImageReader> readers = new ConcurrentHashMap<>();

    /**

     * Returns an {@code ImageReader} to read from the given image file

     */

    public static ImageReader get(Path jimage) throws IOException {

        Objects.requireNonNull(jimage);

        try {

            return readers.computeIfAbsent(jimage, OPENER);

        } catch (UncheckedIOException io) {

            throw io.getCause();

        }

    }

    private static Function<Path, ImageReader> OPENER = new Function<Path, ImageReader>() {

        public ImageReader apply(Path path) {

            try {

                return ImageReader.open(path);

            } catch (IOException io) {

                throw new UncheckedIOException(io);

            }

        }

    };

    /**

     * Returns the {@code ImageReader} to read the image file in this

     * run-time image.

     *

     * @throws UncheckedIOException if an I/O error occurs

     */

    public static ImageReader getImageReader() {

        try {

            return get(BOOT_MODULES_JIMAGE);

        } catch (IOException ioe) {

            throw new UncheckedIOException(ioe);

        }

    }

}