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 
17 package com.android.dx.dex.file;
18 
19 import com.android.dx.rop.cst.Constant;
20 import com.android.dx.util.AnnotatedOutput;
21 import java.util.Collection;
22 
23 /**
24  * A section of a {@code .dex} file which consists of a sequence of
25  * {@link Item} objects. Each of the items must have the same size in
26  * the output.
27  */
28 public abstract class UniformItemSection extends Section {
29     /**
30      * Constructs an instance. The file offset is initially unknown.
31      *
32      * @param name {@code null-ok;} the name of this instance, for annotation
33      * purposes
34      * @param file {@code non-null;} file that this instance is part of
35      * @param alignment {@code > 0;} alignment requirement for the final output;
36      * must be a power of 2
37      */
UniformItemSection(String name, DexFile file, int alignment)38     public UniformItemSection(String name, DexFile file, int alignment) {
39         super(name, file, alignment);
40     }
41 
42     /** {@inheritDoc} */
43     @Override
writeSize()44     public final int writeSize() {
45         Collection<? extends Item> items = items();
46         int sz = items.size();
47 
48         if (sz == 0) {
49             return 0;
50         }
51 
52         // Since each item has to be the same size, we can pick any.
53         return sz * items.iterator().next().writeSize();
54     }
55 
56     /**
57      * Gets the item corresponding to the given {@link Constant}. This
58      * will throw an exception if the constant is not found, including
59      * if this instance isn't the sort that maps constants to {@link
60      * IndexedItem} instances.
61      *
62      * @param cst {@code non-null;} constant to look for
63      * @return {@code non-null;} the corresponding item found in this instance
64      */
get(Constant cst)65     public abstract IndexedItem get(Constant cst);
66 
67     /** {@inheritDoc} */
68     @Override
prepare0()69     protected final void prepare0() {
70         DexFile file = getFile();
71 
72         orderItems();
73 
74         for (Item one : items()) {
75             one.addContents(file);
76         }
77     }
78 
79     /** {@inheritDoc} */
80     @Override
writeTo0(AnnotatedOutput out)81     protected final void writeTo0(AnnotatedOutput out) {
82         DexFile file = getFile();
83         int alignment = getAlignment();
84 
85         for (Item one : items()) {
86             one.writeTo(file, out);
87             out.alignTo(alignment);
88         }
89     }
90 
91     /** {@inheritDoc} */
92     @Override
getAbsoluteItemOffset(Item item)93     public final int getAbsoluteItemOffset(Item item) {
94         /*
95          * Since all items must be the same size, we can use the size
96          * of the one we're given to calculate its offset.
97          */
98         IndexedItem ii = (IndexedItem) item;
99         int relativeOffset = ii.getIndex() * ii.writeSize();
100 
101         return getAbsoluteOffset(relativeOffset);
102     }
103 
104     /**
105      * Alters or picks the order for items in this instance if desired,
106      * so that subsequent calls to {@link #items} will yield a
107      * so-ordered collection. If the items in this instance are indexed,
108      * then this method should also assign indices.
109      */
orderItems()110     protected abstract void orderItems();
111 }
112