1/*
2 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package java.util.jar;
27
28import java.util.zip.*;
29import java.io.*;
30
31/**
32 * The <code>JarOutputStream</code> class is used to write the contents
33 * of a JAR file to any output stream. It extends the class
34 * <code>java.util.zip.ZipOutputStream</code> with support
35 * for writing an optional <code>Manifest</code> entry. The
36 * <code>Manifest</code> can be used to specify meta-information about
37 * the JAR file and its entries.
38 *
39 * @author  David Connelly
40 * @see     Manifest
41 * @see     java.util.zip.ZipOutputStream
42 * @since   1.2
43 */
44public
45class JarOutputStream extends ZipOutputStream {
46    private static final int JAR_MAGIC = 0xCAFE;
47
48    /**
49     * Creates a new <code>JarOutputStream</code> with the specified
50     * <code>Manifest</code>. The manifest is written as the first
51     * entry to the output stream.
52     *
53     * @param out the actual output stream
54     * @param man the optional <code>Manifest</code>
55     * @exception IOException if an I/O error has occurred
56     */
57    public JarOutputStream(OutputStream out, Manifest man) throws IOException {
58        super(out);
59        if (man == null) {
60            throw new NullPointerException("man");
61        }
62        ZipEntry e = new ZipEntry(JarFile.MANIFEST_NAME);
63        putNextEntry(e);
64        man.write(new BufferedOutputStream(this));
65        closeEntry();
66    }
67
68    /**
69     * Creates a new <code>JarOutputStream</code> with no manifest.
70     * @param out the actual output stream
71     * @exception IOException if an I/O error has occurred
72     */
73    public JarOutputStream(OutputStream out) throws IOException {
74        super(out);
75    }
76
77    /**
78     * Begins writing a new JAR file entry and positions the stream
79     * to the start of the entry data. This method will also close
80     * any previous entry. The default compression method will be
81     * used if no compression method was specified for the entry.
82     * The current time will be used if the entry has no set modification
83     * time.
84     *
85     * @param ze the ZIP/JAR entry to be written
86     * @exception ZipException if a ZIP error has occurred
87     * @exception IOException if an I/O error has occurred
88     */
89    public void putNextEntry(ZipEntry ze) throws IOException {
90        if (firstEntry) {
91            // Make sure that extra field data for first JAR
92            // entry includes JAR magic number id.
93            byte[] edata = ze.getExtra();
94            if (edata == null || !hasMagic(edata)) {
95                if (edata == null) {
96                    edata = new byte[4];
97                } else {
98                    // Prepend magic to existing extra data
99                    byte[] tmp = new byte[edata.length + 4];
100                    System.arraycopy(edata, 0, tmp, 4, edata.length);
101                    edata = tmp;
102                }
103                set16(edata, 0, JAR_MAGIC); // extra field id
104                set16(edata, 2, 0);         // extra field size
105                ze.setExtra(edata);
106            }
107            firstEntry = false;
108        }
109        super.putNextEntry(ze);
110    }
111
112    private boolean firstEntry = true;
113
114    /*
115     * Returns true if specified byte array contains the
116     * jar magic extra field id.
117     */
118    private static boolean hasMagic(byte[] edata) {
119        try {
120            int i = 0;
121            while (i < edata.length) {
122                if (get16(edata, i) == JAR_MAGIC) {
123                    return true;
124                }
125                i += get16(edata, i + 2) + 4;
126            }
127        } catch (ArrayIndexOutOfBoundsException e) {
128            // Invalid extra field data
129        }
130        return false;
131    }
132
133    /*
134     * Fetches unsigned 16-bit value from byte array at specified offset.
135     * The bytes are assumed to be in Intel (little-endian) byte order.
136     */
137    private static int get16(byte[] b, int off) {
138        return Byte.toUnsignedInt(b[off]) | ( Byte.toUnsignedInt(b[off+1]) << 8);
139    }
140
141    /*
142     * Sets 16-bit value at specified offset. The bytes are assumed to
143     * be in Intel (little-endian) byte order.
144     */
145    private static void set16(byte[] b, int off, int value) {
146        b[off+0] = (byte)value;
147        b[off+1] = (byte)(value >> 8);
148    }
149}
150