DexFormat.java revision 579d7739c53a2707ad711a2d2cae46d7d782f061 
1/*
2 * Copyright (C) 2011 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.dex;
18
19/**
20 * Constants that show up in and are otherwise related to {@code .dex}
21 * files, and helper methods for same.
22 */
23public final class DexFormat {
24    private DexFormat() {}
25
26    /**
27     * API level to target in order to produce the most modern file
28     * format
29     */
30    public static final int API_CURRENT = 14;
31
32    /** API level to target in order to suppress extended opcode usage */
33    public static final int API_NO_EXTENDED_OPCODES = 13;
34
35    /**
36     * file name of the primary {@code .dex} file inside an
37     * application or library {@code .jar} file
38     */
39    public static final String DEX_IN_JAR_NAME = "classes.dex";
40
41    /** common prefix for all dex file "magic numbers" */
42    public static final String MAGIC_PREFIX = "dex\n";
43
44    /** common suffix for all dex file "magic numbers" */
45    public static final String MAGIC_SUFFIX = "\0";
46
47    /** dex file version number for the current format variant */
48    public static final String VERSION_CURRENT = "036";
49
50    /** dex file version number for API level 13 and earlier */
51    public static final String VERSION_FOR_API_13 = "035";
52
53    /**
54     * value used to indicate endianness of file contents
55     */
56    public static final int ENDIAN_TAG = 0x12345678;
57
58    /**
59     * Returns the API level corresponding to the given magic number,
60     * or {@code -1} if the given array is not a well-formed dex file
61     * magic number.
62     */
63    public static int magicToApi(byte[] magic) {
64        if (magic.length != 8) {
65            return -1;
66        }
67
68        if ((magic[0] != 'd') || (magic[1] != 'e') || (magic[2] != 'x') || (magic[3] != '\n') ||
69                (magic[7] != '\0')) {
70            return -1;
71        }
72
73        String version = "" + ((char) magic[4]) + ((char) magic[5]) +((char) magic[6]);
74
75        if (version.equals(VERSION_CURRENT)) {
76            return API_CURRENT;
77        } else if (version.equals(VERSION_FOR_API_13)) {
78            return 13;
79        }
80
81        return -1;
82    }
83
84    /**
85     * Returns the magic number corresponding to the given target API level.
86     */
87    public static String apiToMagic(int targetApiLevel) {
88        String version;
89
90        if (targetApiLevel >= API_CURRENT) {
91            version = VERSION_CURRENT;
92        } else {
93            version = VERSION_FOR_API_13;
94        }
95
96        return MAGIC_PREFIX + version + MAGIC_SUFFIX;
97    }
98}
99