/*

 * Copyright (c) 2014, 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.nio.ByteBuffer;

import java.nio.IntBuffer;

import java.util.Objects;

/**

 * @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 final class ImageHeader {

    public static final int MAGIC = 0xCAFEDADA;

    public static final int MAJOR_VERSION = 1;

    public static final int MINOR_VERSION = 0;

    private static final int HEADER_SLOTS = 7;

    private final int magic;

    private final int majorVersion;

    private final int minorVersion;

    private final int flags;

    private final int resourceCount;

    private final int tableLength;

    private final int locationsSize;

    private final int stringsSize;

    public ImageHeader(int resourceCount, int tableCount,

            int locationsSize, int stringsSize) {

        this(MAGIC, MAJOR_VERSION, MINOR_VERSION, 0, resourceCount,

                tableCount, locationsSize, stringsSize);

    }

    public ImageHeader(int magic, int majorVersion, int minorVersion,

                int flags, int resourceCount,

                int tableLength, int locationsSize, int stringsSize)

    {

        this.magic = magic;

        this.majorVersion = majorVersion;

        this.minorVersion = minorVersion;

        this.flags = flags;

        this.resourceCount = resourceCount;

        this.tableLength = tableLength;

        this.locationsSize = locationsSize;

        this.stringsSize = stringsSize;

    }

    public static int getHeaderSize() {

       return HEADER_SLOTS * 4;

    }

    static ImageHeader readFrom(IntBuffer buffer) {

        Objects.requireNonNull(buffer);

        if (buffer.capacity() != HEADER_SLOTS) {

            throw new InternalError(

                "jimage header not the correct size: " + buffer.capacity());

        }

        int magic = buffer.get(0);

        int version = buffer.get(1);

        int majorVersion = version >>> 16;

        int minorVersion = version & 0xFFFF;

        int flags = buffer.get(2);

        int resourceCount = buffer.get(3);

        int tableLength = buffer.get(4);

        int locationsSize = buffer.get(5);

        int stringsSize = buffer.get(6);

        return new ImageHeader(magic, majorVersion, minorVersion, flags,

            resourceCount, tableLength, locationsSize, stringsSize);

    }

    public void writeTo(ImageStream stream) {

        Objects.requireNonNull(stream);

        stream.ensure(getHeaderSize());

        writeTo(stream.getBuffer());

    }

    public void writeTo(ByteBuffer buffer) {

        Objects.requireNonNull(buffer);

        buffer.putInt(magic);

        buffer.putInt(majorVersion << 16 | minorVersion);

        buffer.putInt(flags);

        buffer.putInt(resourceCount);

        buffer.putInt(tableLength);

        buffer.putInt(locationsSize);

        buffer.putInt(stringsSize);

    }

    public int getMagic() {

        return magic;

    }

    public int getMajorVersion() {

        return majorVersion;

    }

    public int getMinorVersion() {

        return minorVersion;

    }

    public int getFlags() {

        return flags;

    }

    public int getResourceCount() {

        return resourceCount;

    }

    public int getTableLength() {

        return tableLength;

    }

    public int getRedirectSize() {

        return tableLength * 4;

    }

    public int getOffsetsSize() {

        return tableLength * 4;

    }

    public int getLocationsSize() {

        return locationsSize;

    }

    public int getStringsSize() {

        return stringsSize;

    }

    public int getIndexSize() {

        return getHeaderSize() +

               getRedirectSize() +

               getOffsetsSize() +

               getLocationsSize() +

               getStringsSize();

    }

    int getRedirectOffset() {

        return getHeaderSize();

    }

    int getOffsetsOffset() {

        return getRedirectOffset() +

               getRedirectSize();

    }

    int getLocationsOffset() {

        return getOffsetsOffset() +

               getOffsetsSize();

    }

    int getStringsOffset() {

        return getLocationsOffset() +

               getLocationsSize();

    }

}