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.dexgen.dex.file;
18 
19 import com.android.dexgen.rop.cst.CstUtf8;
20 import com.android.dexgen.util.AnnotatedOutput;
21 import com.android.dexgen.util.Hex;
22 
23 /**
24  * File header section of a {@code .dex} file.
25  */
26 public final class HeaderItem extends IndexedItem {
27     /**
28      * {@code non-null;} the file format magic number, represented as the
29      * low-order bytes of a string
30      */
31     private static final String MAGIC = "dex\n035\0";
32 
33     /** size of this section, in bytes */
34     private static final int HEADER_SIZE = 0x70;
35 
36     /** the endianness tag */
37     private static final int ENDIAN_TAG = 0x12345678;
38 
39     /**
40      * Constructs an instance.
41      */
HeaderItem()42     public HeaderItem() {
43         // This space intentionally left blank.
44     }
45 
46     /** {@inheritDoc} */
47     @Override
itemType()48     public ItemType itemType() {
49         return ItemType.TYPE_HEADER_ITEM;
50     }
51 
52     /** {@inheritDoc} */
53     @Override
writeSize()54     public int writeSize() {
55         return HEADER_SIZE;
56     }
57 
58     /** {@inheritDoc} */
59     @Override
addContents(DexFile file)60     public void addContents(DexFile file) {
61         // Nothing to do here.
62     }
63 
64     /** {@inheritDoc} */
65     @Override
writeTo(DexFile file, AnnotatedOutput out)66     public void writeTo(DexFile file, AnnotatedOutput out) {
67         int mapOff = file.getMap().getFileOffset();
68         Section firstDataSection = file.getFirstDataSection();
69         Section lastDataSection = file.getLastDataSection();
70         int dataOff = firstDataSection.getFileOffset();
71         int dataSize = lastDataSection.getFileOffset() +
72             lastDataSection.writeSize() - dataOff;
73 
74         if (out.annotates()) {
75             out.annotate(8, "magic: " + new CstUtf8(MAGIC).toQuoted());
76             out.annotate(4, "checksum");
77             out.annotate(20, "signature");
78             out.annotate(4, "file_size:       " +
79                          Hex.u4(file.getFileSize()));
80             out.annotate(4, "header_size:     " + Hex.u4(HEADER_SIZE));
81             out.annotate(4, "endian_tag:      " + Hex.u4(ENDIAN_TAG));
82             out.annotate(4, "link_size:       0");
83             out.annotate(4, "link_off:        0");
84             out.annotate(4, "map_off:         " + Hex.u4(mapOff));
85         }
86 
87         // Write the magic number.
88         for (int i = 0; i < 8; i++) {
89             out.writeByte(MAGIC.charAt(i));
90         }
91 
92         // Leave space for the checksum and signature.
93         out.writeZeroes(24);
94 
95         out.writeInt(file.getFileSize());
96         out.writeInt(HEADER_SIZE);
97         out.writeInt(ENDIAN_TAG);
98 
99         /*
100          * Write zeroes for the link size and data, as the output
101          * isn't a staticly linked file.
102          */
103         out.writeZeroes(8);
104 
105         out.writeInt(mapOff);
106 
107         // Write out each section's respective header part.
108         file.getStringIds().writeHeaderPart(out);
109         file.getTypeIds().writeHeaderPart(out);
110         file.getProtoIds().writeHeaderPart(out);
111         file.getFieldIds().writeHeaderPart(out);
112         file.getMethodIds().writeHeaderPart(out);
113         file.getClassDefs().writeHeaderPart(out);
114 
115         if (out.annotates()) {
116             out.annotate(4, "data_size:       " + Hex.u4(dataSize));
117             out.annotate(4, "data_off:        " + Hex.u4(dataOff));
118         }
119 
120         out.writeInt(dataSize);
121         out.writeInt(dataOff);
122     }
123 }
124