Source Home >> Java Source 1.6.0 >> java.util.jar.JarOutputStream V 0.09

001/*
002 * @(#)JarOutputStream.java	1.24 07/01/09
003 *
004 * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
005 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
006 */
007
008package java.util.jar;
009
010import java.util.zip.*;
011import java.io.*;
012
013/**
014 * The <code>JarOutputStream</code> class is used to write the contents
015 * of a JAR file to any output stream. It extends the class
016 * <code>java.util.zip.ZipOutputStream</code> with support
017 * for writing an optional <code>Manifest</code> entry. The
018 * <code>Manifest</code> can be used to specify meta-information about
019 * the JAR file and its entries.
020 *
021 * @author  David Connelly
022 * @version 1.24, 01/09/07
023 * @see	    Manifest
024 * @see	    java.util.zip.ZipOutputStream
025 * @since   1.2
026 */
027public
028class JarOutputStream extends ZipOutputStream {
029    private static final int JAR_MAGIC = 0xCAFE;
030
031    /**
032     * Creates a new <code>JarOutputStream</code> with the specified
033     * <code>Manifest</code>. The manifest is written as the first
034     * entry to the output stream.
035     *
036     * @param out the actual output stream
037     * @param man the optional <code>Manifest</code>
038     * @exception IOException if an I/O error has occurred
039     */
040    public JarOutputStream(OutputStream out, Manifest man) throws IOException {
041	super(out);
042	if (man == null) {
043	    throw new NullPointerException("man");
044	}
045	ZipEntry e = new ZipEntry(JarFile.MANIFEST_NAME);
046	putNextEntry(e);
047	man.write(new BufferedOutputStream(this));
048	closeEntry();
049    }
050
051    /**
052     * Creates a new <code>JarOutputStream</code> with no manifest.
053     * @param out the actual output stream
054     * @exception IOException if an I/O error has occurred
055     */
056    public JarOutputStream(OutputStream out) throws IOException {
057	super(out);
058    }
059
060    /**
061     * Begins writing a new JAR file entry and positions the stream
062     * to the start of the entry data. This method will also close
063     * any previous entry. The default compression method will be
064     * used if no compression method was specified for the entry.
065     * The current time will be used if the entry has no set modification
066     * time.
067     *
068     * @param ze the ZIP/JAR entry to be written
069     * @exception ZipException if a ZIP error has occurred
070     * @exception IOException if an I/O error has occurred
071     */
072    public void putNextEntry(ZipEntry ze) throws IOException {
073	if (firstEntry) {
074	    // Make sure that extra field data for first JAR
075	    // entry includes JAR magic number id.
076	    byte[] edata = ze.getExtra();
077            if (edata == null || !hasMagic(edata)) {
078                if (edata == null) {
079                    edata = new byte[4];
080                } else {
081                    // Prepend magic to existing extra data
082                    byte[] tmp = new byte[edata.length + 4];
083                    System.arraycopy(edata, 0, tmp, 4, edata.length);
084                    edata = tmp;
085                }
086                set16(edata, 0, JAR_MAGIC); // extra field id
087                set16(edata, 2, 0);         // extra field size
088                ze.setExtra(edata);
089	    }
090	    firstEntry = false;
091	}
092	super.putNextEntry(ze);
093    }
094
095    private boolean firstEntry = true;
096
097    /*
098     * Returns true if specified byte array contains the
099     * jar magic extra field id.
100     */
101    private static boolean hasMagic(byte[] edata) {
102	try {
103	    int i = 0;
104	    while (i < edata.length) {
105		if (get16(edata, i) == JAR_MAGIC) {
106		    return true;
107		}
108		i += get16(edata, i + 2) + 4;
109	    }
110	} catch (ArrayIndexOutOfBoundsException e) {
111	    // Invalid extra field data
112	}
113	return false;
114    }
115
116    /*
117     * Fetches unsigned 16-bit value from byte array at specified offset.
118     * The bytes are assumed to be in Intel (little-endian) byte order.
119     */
120    private static int get16(byte[] b, int off) {
121	return (b[off] & 0xff) | ((b[off+1] & 0xff) << 8);
122    }
123
124    /*
125     * Sets 16-bit value at specified offset. The bytes are assumed to
126     * be in Intel (little-endian) byte order.
127     */
128    private static void set16(byte[] b, int off, int value) {
129	b[off+0] = (byte)value;
130	b[off+1] = (byte)(value >> 8);
131    }
132}