StringDataItem.java revision 1f29ee7351fd7fb48bb093b39b5f9ffddb34a3ea 
1/*
2 * [The "BSD licence"]
3 * Copyright (c) 2010 Ben Gruver (JesusFreke)
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. The name of the author may not be used to endorse or promote products
15 *    derived from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29package org.jf.dexlib;
30
31import org.jf.dexlib.Util.*;
32
33public class StringDataItem extends Item<StringDataItem> {
34    private int hashCode = 0;
35
36    private String stringValue;
37
38    /**
39     * Creates a new uninitialized <code>StringDataItem</code>
40     * @param dexFile The <code>DexFile</code> that this item belongs to
41     */
42    protected StringDataItem(DexFile dexFile) {
43        super(dexFile);
44    }
45
46    /**
47     * Creates a new <code>StringDataItem</code> for the given string
48     * @param dexFile The <code>DexFile</code> that this item belongs to
49     * @param stringValue The string value that this item represents
50     */
51    private StringDataItem(DexFile dexFile, String stringValue) {
52        super(dexFile);
53
54        this.stringValue = stringValue;
55    }
56
57    /**
58     * Returns a <code>StringDataItem</code> for the given values, and that has been interned into
59     * the given <code>DexFile</code>
60     * @param dexFile The <code>DexFile</code> that this item belongs to
61     * @param value The string value that this item represents
62     * @return a <code>StringDataItem</code> for the given values, and that has been interned into
63     * the given <code>DexFile</code>
64     */
65    public static StringDataItem internStringDataItem(DexFile dexFile, String value) {
66        StringDataItem StringDataItem = new StringDataItem(dexFile, value);
67        return dexFile.StringDataSection.intern(StringDataItem);
68    }
69
70    /**
71     * Looks up the <code>StringDataItem</code> from the given <code>DexFile</code> for the given
72     * string value
73     * @param dexFile the <code>Dexfile</code> to find the string value in
74     * @param value The string value to look up
75     * @return a <code>StringDataItem</code> from the given <code>DexFile</code> for the given
76     * string value, or null if it doesn't exist
77     **/
78    public static StringDataItem lookupStringDataItem(DexFile dexFile, String value) {
79        StringDataItem StringDataItem = new StringDataItem(dexFile, value);
80        return dexFile.StringDataSection.getInternedItem(StringDataItem);
81    }
82
83    /** {@inheritDoc} */
84    protected void readItem(Input in, ReadContext readContext) {
85        in.readUnsignedLeb128(); //string length
86        stringValue = in.realNullTerminatedUtf8String();
87    }
88
89    /** {@inheritDoc} */
90    protected int placeItem(int offset) {
91        return offset + Leb128Utils.unsignedLeb128Size(stringValue.length()) +
92                Utf8Utils.stringToUtf8Bytes(stringValue).length + 1;
93    }
94
95    /** {@inheritDoc} */
96    protected void writeItem(AnnotatedOutput out) {
97        byte[] encodedValue = Utf8Utils.stringToUtf8Bytes(stringValue);
98        if (out.annotates()) {
99            out.annotate("string_size: 0x" + Integer.toHexString(stringValue.length()) + " (" + stringValue.length() +
100                    ")");
101            out.writeUnsignedLeb128(stringValue.length());
102
103            out.annotate(encodedValue.length + 1, "string_data: \"" + Utf8Utils.escapeString(stringValue) + "\"");
104        } else {
105            out.writeUnsignedLeb128(stringValue.length());
106        }
107        out.write(encodedValue);
108        out.writeByte(0);
109    }
110
111    /** {@inheritDoc} */
112    public ItemType getItemType() {
113        return ItemType.TYPE_STRING_DATA_ITEM;
114    }
115
116    /** {@inheritDoc} */
117    public String getConciseIdentity() {
118        return "string_data_item: \"" + Utf8Utils.escapeString(getStringValue()) + "\"";
119    }
120
121    /** {@inheritDoc} */
122    public int compareTo(StringDataItem o) {
123        return getStringValue().compareTo(o.getStringValue());
124    }
125
126    /**
127     * Get the string value of this item as a <code>String</code>
128     * @return the string value of this item as a String
129     */
130    public String getStringValue() {
131        return stringValue;
132    }
133
134    /**
135     * calculate and cache the hashcode
136     */
137    private void calcHashCode() {
138        hashCode = getStringValue().hashCode();
139    }
140
141    @Override
142    public int hashCode() {
143        //there's a small possibility that the actual hash code will be 0. If so, we'll
144        //just end up recalculating it each time
145        if (hashCode == 0)
146            calcHashCode();
147        return hashCode;
148    }
149
150    @Override
151    public boolean equals(Object o) {
152        if (this==o) {
153            return true;
154        }
155        if (o==null || !this.getClass().equals(o.getClass())) {
156            return false;
157        }
158
159        //This assumes that the referenced items have been interned in both objects.
160        //This is a valid assumption because all outside code must use the static
161        //"getInterned..." style methods to make new items, and any item created
162        //internally is guaranteed to be interned
163        StringDataItem other = (StringDataItem)o;
164        return getStringValue().equals(other.getStringValue());
165    }
166}
167