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 { 24 private DexFormat() {} 25 26 /** API level to target in order to generate const-method-handle and const-method-type */ 27 public static final int API_CONST_METHOD_HANDLE = 28; 28 29 /** API level to target in order to generate invoke-polymorphic and invoke-custom */ 30 public static final int API_METHOD_HANDLES = 26; 31 32 /** API level to target in order to define default and static interface methods */ 33 public static final int API_DEFINE_INTERFACE_METHODS = 24; 34 35 /** API level to target in order to invoke default and static interface methods */ 36 public static final int API_INVOKE_INTERFACE_METHODS = 24; 37 38 /** API level at which the invocation of static interface methods is permitted by dx. 39 * This value has been determined experimentally by testing on different VM versions. */ 40 public static final int API_INVOKE_STATIC_INTERFACE_METHODS = 21; 41 42 /** API level to target in order to suppress extended opcode usage */ 43 public static final int API_NO_EXTENDED_OPCODES = 13; 44 45 /** 46 * API level to target in order to produce the most modern file 47 * format 48 */ 49 public static final int API_CURRENT = API_CONST_METHOD_HANDLE; 50 51 /** dex file version number for API level 28 and earlier */ 52 public static final String VERSION_FOR_API_28 = "039"; 53 54 /** dex file version number for API level 26 and earlier */ 55 public static final String VERSION_FOR_API_26 = "038"; 56 57 /** dex file version number for API level 24 and earlier */ 58 public static final String VERSION_FOR_API_24 = "037"; 59 60 /** dex file version number for API level 13 and earlier */ 61 public static final String VERSION_FOR_API_13 = "035"; 62 63 /** 64 * Dex file version number for dalvik. 65 * <p> 66 * Note: Dex version 36 was loadable in some versions of Dalvik but was never fully supported or 67 * completed and is not considered a valid dex file format. 68 * </p> 69 */ 70 public static final String VERSION_CURRENT = VERSION_FOR_API_28; 71 72 /** 73 * file name of the primary {@code .dex} file inside an 74 * application or library {@code .jar} file 75 */ 76 public static final String DEX_IN_JAR_NAME = "classes.dex"; 77 78 /** common prefix for all dex file "magic numbers" */ 79 public static final String MAGIC_PREFIX = "dex\n"; 80 81 /** common suffix for all dex file "magic numbers" */ 82 public static final String MAGIC_SUFFIX = "\0"; 83 84 /** 85 * value used to indicate endianness of file contents 86 */ 87 public static final int ENDIAN_TAG = 0x12345678; 88 89 /** 90 * Maximum addressable field or method index. 91 * The largest addressable member is 0xffff, in the "instruction formats" spec as field@CCCC or 92 * meth@CCCC. 93 */ 94 public static final int MAX_MEMBER_IDX = 0xFFFF; 95 96 /** 97 * Maximum addressable type index. 98 * The largest addressable type is 0xffff, in the "instruction formats" spec as type@CCCC. 99 */ 100 public static final int MAX_TYPE_IDX = 0xFFFF; 101 102 /** 103 * Returns the API level corresponding to the given magic number, 104 * or {@code -1} if the given array is not a well-formed dex file 105 * magic number. 106 * 107 * @param magic array of bytes containing DEX file magic string 108 * @return API level corresponding to magic string if valid, -1 otherwise. 109 */ 110 public static int magicToApi(byte[] magic) { 111 if (magic.length != 8) { 112 return -1; 113 } 114 115 if ((magic[0] != 'd') || (magic[1] != 'e') || (magic[2] != 'x') || (magic[3] != '\n') || 116 (magic[7] != '\0')) { 117 return -1; 118 } 119 120 String version = "" + ((char) magic[4]) + ((char) magic[5]) +((char) magic[6]); 121 122 if (version.equals(VERSION_FOR_API_13)) { 123 return API_NO_EXTENDED_OPCODES; 124 } else if (version.equals(VERSION_FOR_API_24)) { 125 return API_DEFINE_INTERFACE_METHODS; 126 } else if (version.equals(VERSION_FOR_API_26)) { 127 return API_METHOD_HANDLES; 128 } else if (version.equals(VERSION_FOR_API_28)) { 129 return API_CONST_METHOD_HANDLE; 130 } else if (version.equals(VERSION_CURRENT)) { 131 return API_CURRENT; 132 } 133 134 return -1; 135 } 136 137 /** 138 * Returns the magic number corresponding to the given target API level. 139 * 140 * @param targetApiLevel level of API (minimum supported value 13). 141 * @return Magic string corresponding to API level supplied. 142 */ 143 public static String apiToMagic(int targetApiLevel) { 144 String version; 145 146 if (targetApiLevel >= API_CURRENT) { 147 version = VERSION_CURRENT; 148 } else if (targetApiLevel >= API_CONST_METHOD_HANDLE) { 149 version = VERSION_FOR_API_28; 150 } else if (targetApiLevel >= API_METHOD_HANDLES) { 151 version = VERSION_FOR_API_26; 152 } else if (targetApiLevel >= API_DEFINE_INTERFACE_METHODS) { 153 version = VERSION_FOR_API_24; 154 } else { 155 version = VERSION_FOR_API_13; 156 } 157 158 return MAGIC_PREFIX + version + MAGIC_SUFFIX; 159 } 160 161 /** 162 * Checks whether a DEX file magic string is supported. 163 * @param magic string from DEX file 164 * @return 165 */ 166 public static boolean isSupportedDexMagic(byte[] magic) { 167 int api = magicToApi(magic); 168 return api > 0; 169 } 170 } 171
