/*
 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package java.util.jar;

import java.util.zip.*;
import java.io.*;

/**
 * The <code>JarOutputStream</code> class is used to write the contents
 * of a JAR file to any output stream. It extends the class
 * <code>java.util.zip.ZipOutputStream</code> with support
 * for writing an optional <code>Manifest</code> entry. The
 * <code>Manifest</code> 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</code> with the specified
 * <code>Manifest</code>. The manifest is written as the first
 * entry to the output stream.
 *
 * @param out the actual output stream
 * @param man the optional <code>Manifest</code>
 * @exception 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</code> with no manifest.
 * @param out the actual output stream
 * @exception 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. The default compression method will be
 * used if no compression method was specified for the entry.
 * The current time will be used if the entry has no set modification
 * time.
 *
 * @param ze the ZIP/JAR entry to be written
 * @exception ZipException if a ZIP error has occurred
 * @exception 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);
 }
}