/*

 * 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

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 */

package jdk.internal.jimage.decompressor;

import java.nio.ByteBuffer;

import java.nio.ByteOrder;

import java.util.Objects;

import jdk.internal.jimage.decompressor.ResourceDecompressor.StringsProvider;

/**

 *

 * A resource header for compressed resource. This class is handled internally,

 * you don't have to add header to the resource, headers are added automatically

 * for compressed resources.

 *

 * @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 CompressedResourceHeader {

    private static final int SIZE = 29;

    public static final int MAGIC = 0xCAFEFAFA;

    private final long uncompressedSize;

    private final long compressedSize;

    private final int decompressorNameOffset;

    private final int contentOffset;

    private final boolean isTerminal;

    public CompressedResourceHeader(long compressedSize,

            long uncompressedSize, int decompressorNameOffset, int contentOffset,

            boolean isTerminal) {

        this.compressedSize = compressedSize;

        this.uncompressedSize = uncompressedSize;

        this.decompressorNameOffset = decompressorNameOffset;

        this.contentOffset = contentOffset;

        this.isTerminal = isTerminal;

    }

    public boolean isTerminal() {

        return isTerminal;

    }

    public int getDecompressorNameOffset() {

        return decompressorNameOffset;

    }

    public int getContentOffset() {

        return contentOffset;

    }

    public String getStoredContent(StringsProvider provider) {

        Objects.requireNonNull(provider);

        if(contentOffset == -1) {

            return null;

        }

        return provider.getString(contentOffset);

    }

    public long getUncompressedSize() {

        return uncompressedSize;

    }

    public long getResourceSize() {

        return compressedSize;

    }

    public byte[] getBytes(ByteOrder order) {

        Objects.requireNonNull(order);

        ByteBuffer buffer = ByteBuffer.allocate(SIZE);

        buffer.order(order);

        buffer.putInt(MAGIC);

        buffer.putLong(compressedSize);

        buffer.putLong(uncompressedSize);

        buffer.putInt(decompressorNameOffset);

        buffer.putInt(contentOffset);

        buffer.put(isTerminal ? (byte)1 : (byte)0);

        return buffer.array();

    }

    public static int getSize() {

        return SIZE;

    }

    public static CompressedResourceHeader readFromResource(ByteOrder order,

            byte[] resource) {

        Objects.requireNonNull(order);

        Objects.requireNonNull(resource);

        if (resource.length < getSize()) {

            return null;

        }

        ByteBuffer buffer = ByteBuffer.wrap(resource, 0, SIZE);

        buffer.order(order);

        int magic = buffer.getInt();

        if(magic != MAGIC) {

            return null;

        }

        long size = buffer.getLong();

        long uncompressedSize = buffer.getLong();

        int decompressorNameOffset = buffer.getInt();

        int contentIndex = buffer.getInt();

        byte isTerminal = buffer.get();

        return new CompressedResourceHeader(size, uncompressedSize,

                decompressorNameOffset, contentIndex, isTerminal == 1);

    }

}