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 17 package com.android.dex; 18 19 /** 20 * Constants that show up in and are otherwise related to {@code .dex} 21 * files, and helper methods for same. 22 */ 23 public final class DexFormat { 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 = 24; 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 /** 48 * Dex file version number for dalvik. 49 * <p> 50 * Note: Dex version 36 was loadable in some versions of Dalvik but was never fully supported or 51 * completed and is not considered a valid dex file format. 52 * </p> 53 */ 54 public static final String VERSION_CURRENT = "037"; 55 56 /** dex file version number for API level 13 and earlier */ 57 public static final String VERSION_FOR_API_13 = "035"; 58 59 /** 60 * value used to indicate endianness of file contents 61 */ 62 public static final int ENDIAN_TAG = 0x12345678; 63 64 /** 65 * Maximum addressable field or method index. 66 * The largest addressable member is 0xffff, in the "instruction formats" spec as field@CCCC or 67 * meth@CCCC. 68 */ 69 public static final int MAX_MEMBER_IDX = 0xFFFF; 70 71 /** 72 * Maximum addressable type index. 73 * The largest addressable type is 0xffff, in the "instruction formats" spec as type@CCCC. 74 */ 75 public static final int MAX_TYPE_IDX = 0xFFFF; 76 77 /** 78 * Returns the API level corresponding to the given magic number, 79 * or {@code -1} if the given array is not a well-formed dex file 80 * magic number. 81 */ magicToApi(byte[] magic)82 public static int magicToApi(byte[] magic) { 83 if (magic.length != 8) { 84 return -1; 85 } 86 87 if ((magic[0] != 'd') || (magic[1] != 'e') || (magic[2] != 'x') || (magic[3] != '\n') || 88 (magic[7] != '\0')) { 89 return -1; 90 } 91 92 String version = "" + ((char) magic[4]) + ((char) magic[5]) +((char) magic[6]); 93 94 if (version.equals(VERSION_CURRENT)) { 95 return API_CURRENT; 96 } else if (version.equals(VERSION_FOR_API_13)) { 97 return API_NO_EXTENDED_OPCODES; 98 } 99 100 return -1; 101 } 102 103 /** 104 * Returns the magic number corresponding to the given target API level. 105 */ apiToMagic(int targetApiLevel)106 public static String apiToMagic(int targetApiLevel) { 107 String version; 108 109 if (targetApiLevel >= API_CURRENT) { 110 version = VERSION_CURRENT; 111 } else { 112 version = VERSION_FOR_API_13; 113 } 114 115 return MAGIC_PREFIX + version + MAGIC_SUFFIX; 116 } 117 isSupportedDexMagic(byte[] magic)118 public static boolean isSupportedDexMagic(byte[] magic) { 119 int api = magicToApi(magic); 120 return api == API_NO_EXTENDED_OPCODES || api == API_CURRENT; 121 } 122 } 123