1/*
2 * Copyright (C) 2007 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.dx.cf.direct;
18
19import com.android.dx.cf.attrib.RawAttribute;
20import com.android.dx.cf.iface.Attribute;
21import com.android.dx.cf.iface.ParseException;
22import com.android.dx.cf.iface.ParseObserver;
23import com.android.dx.rop.cst.ConstantPool;
24import com.android.dx.rop.cst.CstString;
25import com.android.dx.util.ByteArray;
26import com.android.dx.util.Hex;
27
28/**
29 * Factory capable of instantiating various {@link Attribute} subclasses
30 * depending on the context and name.
31 */
32public class AttributeFactory {
33    /** context for attributes on class files */
34    public static final int CTX_CLASS = 0;
35
36    /** context for attributes on fields */
37    public static final int CTX_FIELD = 1;
38
39    /** context for attributes on methods */
40    public static final int CTX_METHOD = 2;
41
42    /** context for attributes on code attributes */
43    public static final int CTX_CODE = 3;
44
45    /** number of contexts */
46    public static final int CTX_COUNT = 4;
47
48    /**
49     * Constructs an instance.
50     */
51    public AttributeFactory() {
52        // This space intentionally left blank.
53    }
54
55    /**
56     * Parses and makes an attribute based on the bytes at the
57     * indicated position in the given array. This method figures out
58     * the name, and then does all the setup to call on to {@link #parse0},
59     * which does the actual construction.
60     *
61     * @param cf {@code non-null;} class file to parse from
62     * @param context context to parse in; one of the {@code CTX_*}
63     * constants
64     * @param offset offset into {@code dcf}'s {@code bytes}
65     * to start parsing at
66     * @param observer {@code null-ok;} parse observer to report to, if any
67     * @return {@code non-null;} an appropriately-constructed {@link Attribute}
68     */
69    public final Attribute parse(DirectClassFile cf, int context, int offset,
70                                 ParseObserver observer) {
71        if (cf == null) {
72            throw new NullPointerException("cf == null");
73        }
74
75        if ((context < 0) || (context >= CTX_COUNT)) {
76            throw new IllegalArgumentException("bad context");
77        }
78
79        CstString name = null;
80
81        try {
82            ByteArray bytes = cf.getBytes();
83            ConstantPool pool = cf.getConstantPool();
84            int nameIdx = bytes.getUnsignedShort(offset);
85            int length = bytes.getInt(offset + 2);
86
87            name = (CstString) pool.get(nameIdx);
88
89            if (observer != null) {
90                observer.parsed(bytes, offset, 2,
91                                "name: " + name.toHuman());
92                observer.parsed(bytes, offset + 2, 4,
93                                "length: " + Hex.u4(length));
94            }
95
96            return parse0(cf, context, name.getString(), offset + 6, length,
97                          observer);
98        } catch (ParseException ex) {
99            ex.addContext("...while parsing " +
100                    ((name != null) ? (name.toHuman() + " ") : "") +
101                    "attribute at offset " + Hex.u4(offset));
102            throw ex;
103        }
104    }
105
106    /**
107     * Parses attribute content. The base class implements this by constructing
108     * an instance of {@link RawAttribute}. Subclasses are expected to
109     * override this to do something better in most cases.
110     *
111     * @param cf {@code non-null;} class file to parse from
112     * @param context context to parse in; one of the {@code CTX_*}
113     * constants
114     * @param name {@code non-null;} the attribute name
115     * @param offset offset into {@code bytes} to start parsing at; this
116     * is the offset to the start of attribute data, not to the header
117     * @param length the length of the attribute data
118     * @param observer {@code null-ok;} parse observer to report to, if any
119     * @return {@code non-null;} an appropriately-constructed {@link Attribute}
120     */
121    protected Attribute parse0(DirectClassFile cf, int context, String name,
122                               int offset, int length,
123                               ParseObserver observer) {
124        ByteArray bytes = cf.getBytes();
125        ConstantPool pool = cf.getConstantPool();
126        Attribute result = new RawAttribute(name, bytes, offset, length, pool);
127
128        if (observer != null) {
129            observer.parsed(bytes, offset, length, "attribute data");
130        }
131
132        return result;
133    }
134}
135