/*

 * Copyright (c) 1997, 2019, 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 java.util.jar;

import java.util.zip.*;

import java.io.*;

/**

 * The {@code JarOutputStream} class is used to write the contents

 * of a JAR file to any output stream. It extends the class

 * {@code java.util.zip.ZipOutputStream} with support

 * for writing an optional {@code Manifest} entry. The

 * {@code Manifest} can be used to specify meta-information about

 * the JAR file and its entries.

 *

 * @author  David Connelly

 * @see     Manifest

 * @see     java.util.zip.ZipOutputStream

 * @since   1.2

 */

public class JarOutputStream extends ZipOutputStream {

    private static final int JAR_MAGIC = 0xCAFE;

    /**

     * Creates a new {@code JarOutputStream} with the specified

     * {@code Manifest}. The manifest is written as the first

     * entry to the output stream.

     *

     * @param out the actual output stream

     * @param man the optional {@code Manifest}

     * @throws    IOException if an I/O error has occurred

     */

    public JarOutputStream(OutputStream out, Manifest man) throws IOException {

        super(out);

        if (man == null) {

            throw new NullPointerException("man");

        }

        ZipEntry e = new ZipEntry(JarFile.MANIFEST_NAME);

        putNextEntry(e);

        man.write(new BufferedOutputStream(this));

        closeEntry();

    }

    /**

     * Creates a new {@code JarOutputStream} with no manifest.

     * @param out the actual output stream

     * @throws    IOException if an I/O error has occurred

     */

    public JarOutputStream(OutputStream out) throws IOException {

        super(out);

    }

    /**

     * Begins writing a new JAR file entry and positions the stream

     * to the start of the entry data. This method will also close

     * any previous entry.

     * <p>

     * The default compression method will be used if no compression

     * method was specified for the entry. When writing a compressed

     * (DEFLATED) entry, and the compressed size has not been explicitly

     * set with the {@link ZipEntry#setCompressedSize(long)} method,

     * then the compressed size will be set to the actual compressed

     * size after deflation.

     * <p>

     * The current time will be used if the entry has no set modification

     * time.

     *

     * @param ze the ZIP/JAR entry to be written

     * @throws    ZipException if a ZIP error has occurred

     * @throws    IOException if an I/O error has occurred

     */

    public void putNextEntry(ZipEntry ze) throws IOException {

        if (firstEntry) {

            // Make sure that extra field data for first JAR

            // entry includes JAR magic number id.

            byte[] edata = ze.getExtra();

            if (edata == null || !hasMagic(edata)) {

                if (edata == null) {

                    edata = new byte[4];

                } else {

                    // Prepend magic to existing extra data

                    byte[] tmp = new byte[edata.length + 4];

                    System.arraycopy(edata, 0, tmp, 4, edata.length);

                    edata = tmp;

                }

                set16(edata, 0, JAR_MAGIC); // extra field id

                set16(edata, 2, 0);         // extra field size

                ze.setExtra(edata);

            }

            firstEntry = false;

        }

        super.putNextEntry(ze);

    }

    private boolean firstEntry = true;

    /*

     * Returns true if specified byte array contains the

     * jar magic extra field id.

     */

    private static boolean hasMagic(byte[] edata) {

        try {

            int i = 0;

            while (i < edata.length) {

                if (get16(edata, i) == JAR_MAGIC) {

                    return true;

                }

                i += get16(edata, i + 2) + 4;

            }

        } catch (ArrayIndexOutOfBoundsException e) {

            // Invalid extra field data

        }

        return false;

    }

    /*

     * Fetches unsigned 16-bit value from byte array at specified offset.

     * The bytes are assumed to be in Intel (little-endian) byte order.

     */

    private static int get16(byte[] b, int off) {

        return Byte.toUnsignedInt(b[off]) | ( Byte.toUnsignedInt(b[off+1]) << 8);

    }

    /*

     * Sets 16-bit value at specified offset. The bytes are assumed to

     * be in Intel (little-endian) byte order.

     */

    private static void set16(byte[] b, int off, int value) {

        b[off+0] = (byte)value;

        b[off+1] = (byte)(value >> 8);

    }

}