source: josm/trunk/src/org/openstreetmap/josm/tools/WindowsShortcut.java @ 13692

Last change on this file since 13692 was 13692, checked in by Don-vip, 7 months ago

see #16243 - do not rely on internal JDK classes, not available on Linux

  • Property svn:eol-style set to native
File size: 8.4 KB
Line 
1// License: GPL. For details, see LICENSE file.
2package org.openstreetmap.josm.tools;
3
4import java.io.ByteArrayOutputStream;
5import java.io.File;
6import java.io.FileInputStream;
7import java.io.IOException;
8import java.io.InputStream;
9import java.text.ParseException;
10
11/**
12 * Represents a Windows shortcut (typically visible to Java only as a '.lnk' file).
13 *
14 * Retrieved 2011-09-23 from http://stackoverflow.com/questions/309495/windows-shortcut-lnk-parser-in-java/672775#672775
15 *
16 * Written by: (the stack overflow users, obviously!)
17 *   Apache Commons VFS dependency removed by crysxd (why were we using that!?) https://github.com/crysxd
18 *   Headerified, refactored and commented by Code Bling http://stackoverflow.com/users/675721/code-bling
19 *   Network file support added by Stefan Cordes http://stackoverflow.com/users/81330/stefan-cordes
20 *   Adapted by Sam Brightman http://stackoverflow.com/users/2492/sam-brightman
21 *   Based on information in 'The Windows Shortcut File Format' by Jesse Hager <jessehager@iname.com>
22 *   And somewhat based on code from the book 'Swing Hacks: Tips and Tools for Killer GUIs'
23 *     by Joshua Marinacci and Chris Adamson
24 *     ISBN: 0-596-00907-0
25 *     http://www.oreilly.com/catalog/swinghks/
26 * @since 13692
27 */
28public class WindowsShortcut {
29    private boolean isDirectory;
30    private boolean isLocal;
31    private String realFile;
32
33    /**
34     * Provides a quick test to see if this could be a valid link !
35     * If you try to instantiate a new WindowShortcut and the link is not valid,
36     * Exceptions may be thrown and Exceptions are extremely slow to generate,
37     * therefore any code needing to loop through several files should first check this.
38     *
39     * @param file the potential link
40     * @return true if may be a link, false otherwise
41     * @throws IOException if an IOException is thrown while reading from the file
42     */
43    public static boolean isPotentialValidLink(File file) throws IOException {
44        final int minimum_length = 0x64;
45        boolean isPotentiallyValid = false;
46        try (InputStream fis = new FileInputStream(file)) {
47            isPotentiallyValid = file.isFile()
48                && file.getName().toLowerCase().endsWith(".lnk")
49                && fis.available() >= minimum_length
50                && isMagicPresent(getBytes(fis, 32));
51        }
52        return isPotentiallyValid;
53    }
54
55    /**
56     * Constructs a new {@code WindowsShortcut}
57     * @param file file
58     * @throws IOException if an I/O error occurs
59     * @throws ParseException if a parsing error occurs
60     */
61    public WindowsShortcut(File file) throws IOException, ParseException {
62        try (InputStream in = new FileInputStream(file)) {
63            parseLink(getBytes(in));
64        }
65    }
66
67    /**
68     * @return the name of the filesystem object pointed to by this shortcut
69     */
70    public String getRealFilename() {
71        return realFile;
72    }
73
74    /**
75     * Tests if the shortcut points to a local resource.
76     * @return true if the 'local' bit is set in this shortcut, false otherwise
77     */
78    public boolean isLocal() {
79        return isLocal;
80    }
81
82    /**
83     * Tests if the shortcut points to a directory.
84     * @return true if the 'directory' bit is set in this shortcut, false otherwise
85     */
86    public boolean isDirectory() {
87        return isDirectory;
88    }
89
90    /**
91     * Gets all the bytes from an InputStream
92     * @param in the InputStream from which to read bytes
93     * @return array of all the bytes contained in 'in'
94     * @throws IOException if an IOException is encountered while reading the data from the InputStream
95     */
96    private static byte[] getBytes(InputStream in) throws IOException {
97        return getBytes(in, null);
98    }
99
100    /**
101     * Gets up to max bytes from an InputStream
102     * @param in the InputStream from which to read bytes
103     * @param max maximum number of bytes to read
104     * @return array of all the bytes contained in 'in'
105     * @throws IOException if an IOException is encountered while reading the data from the InputStream
106     */
107    private static byte[] getBytes(InputStream in, Integer max) throws IOException {
108        // read the entire file into a byte buffer
109        ByteArrayOutputStream bout = new ByteArrayOutputStream();
110        byte[] buff = new byte[256];
111        while (max == null || max > 0) {
112            int n = in.read(buff);
113            if (n == -1) {
114                break;
115            }
116            bout.write(buff, 0, n);
117            if (max != null)
118                max -= n;
119        }
120        in.close();
121        return bout.toByteArray();
122    }
123
124    private static boolean isMagicPresent(byte[] link) {
125        final int magic = 0x0000004C;
126        final int magic_offset = 0x00;
127        return link.length >= 32 && bytesToDword(link, magic_offset) == magic;
128    }
129
130    /**
131     * Gobbles up link data by parsing it and storing info in member fields
132     * @param link all the bytes from the .lnk file
133     * @throws ParseException if a parsing error occurs
134     */
135    private void parseLink(byte[] link) throws ParseException {
136        try {
137            if (!isMagicPresent(link))
138                throw new ParseException("Invalid shortcut; magic is missing", 0);
139
140            // get the flags byte
141            byte flags = link[0x14];
142
143            // get the file attributes byte
144            final int file_atts_offset = 0x18;
145            byte file_atts = link[file_atts_offset];
146            byte is_dir_mask = (byte) 0x10;
147            if ((file_atts & is_dir_mask) > 0) {
148                isDirectory = true;
149            } else {
150                isDirectory = false;
151            }
152
153            // if the shell settings are present, skip them
154            final int shell_offset = 0x4c;
155            final byte has_shell_mask = (byte) 0x01;
156            int shell_len = 0;
157            if ((flags & has_shell_mask) > 0) {
158                // the plus 2 accounts for the length marker itself
159                shell_len = bytesToWord(link, shell_offset) + 2;
160            }
161
162            // get to the file settings
163            int file_start = 0x4c + shell_len;
164
165            final int file_location_info_flag_offset_offset = 0x08;
166            int file_location_info_flag = link[file_start + file_location_info_flag_offset_offset];
167            isLocal = (file_location_info_flag & 2) == 0;
168            // get the local volume and local system values
169            //final int localVolumeTable_offset_offset = 0x0C;
170            final int basename_offset_offset = 0x10;
171            final int networkVolumeTable_offset_offset = 0x14;
172            final int finalname_offset_offset = 0x18;
173            int finalname_offset = link[file_start + finalname_offset_offset] + file_start;
174            String finalname = getNullDelimitedString(link, finalname_offset);
175            if (isLocal) {
176                int basename_offset = link[file_start + basename_offset_offset] + file_start;
177                String basename = getNullDelimitedString(link, basename_offset);
178                realFile = basename + finalname;
179            } else {
180                int networkVolumeTable_offset = link[file_start + networkVolumeTable_offset_offset] + file_start;
181                int shareName_offset_offset = 0x08;
182                int shareName_offset = link[networkVolumeTable_offset + shareName_offset_offset]
183                    + networkVolumeTable_offset;
184                String shareName = getNullDelimitedString(link, shareName_offset);
185                realFile = shareName + "\\" + finalname;
186            }
187        } catch (ArrayIndexOutOfBoundsException e) {
188            ParseException ex = new ParseException("Could not be parsed, probably not a valid WindowsShortcut", 0);
189            ex.initCause(e);
190            throw ex;
191        }
192    }
193
194    private static String getNullDelimitedString(byte[] bytes, int off) {
195        int len = 0;
196        // count bytes until the null character (0)
197        while (true) {
198            if (bytes[off + len] == 0) {
199                break;
200            }
201            len++;
202        }
203        return new String(bytes, off, len);
204    }
205
206    /*
207     * convert two bytes into a short note, this is little endian because it's for an Intel only OS.
208     */
209    private static int bytesToWord(byte[] bytes, int off) {
210        return ((bytes[off + 1] & 0xff) << 8) | (bytes[off] & 0xff);
211    }
212
213    private static int bytesToDword(byte[] bytes, int off) {
214        return (bytesToWord(bytes, off + 2) << 16) | bytesToWord(bytes, off);
215    }
216}
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