在android源码 中的/dalvik/libdex/DexFile.h找到关于dexfile的定义
/*
* Structure representing a DEX file.
*
* Code should regard DexFile as opaque, using the API calls provided here
* to access specific structures.
*/
typedef struct DexFile {
/* directly-mapped "opt" header */
const DexOptHeader* pOptHeader;
/* pointers to directly-mapped structs and arrays in base DEX */
const DexHeader* pHeader;
const DexStringId* pStringIds;
const DexTypeId* pTypeIds;
const DexFieldId* pFieldIds;
const DexMethodId* pMethodIds;
const DexProtoId* pProtoIds;
const DexClassDef* pClassDefs;
const DexLink* pLinkData;
/* mapped in "auxillary" section */
const DexClassLookup* pClassLookup;
/* points to start of DEX file data */
const u1* baseAddr;
/* track memory overhead for auxillary structures */
int overhead;
/* additional app-specific data structures associated with the DEX */
void* auxData;
} DexFile;
先创建java 源文件如下：
public class Hello
{
public static void main(String[] argc)
{
System.out.println(“Hello, Android!\n”);
}
}
在当前工作路径下 ， 编译方法如下 ：
-
- 编译成 java class 文件
执行命令 ： javac Hello.java 编译完成后 ，目录下生成 Hello.class 文件 。可以使用命令 java Hello 来测试下 ，会输出代码中的 “Hello， Android！” 的字符串 。
-
- 编译成 dex 文件
编译工具在 Android SDK 的路径如下 ，其中 19.0.1 是Android SDK build_tools 的版本 ，请按照在本地安装的 build_tools 版本来 。建议该路径加载到 PATH 路径下 ，否则引用 dx 工具时需要使用绝对路径 ：./build-tools/19.0.1/dx
执行命令 ： dx –dex –output=Hello.dex Hello.class
编译正常会生成 Hello.dex 文件 。
-
- 使用 ADB 运行测试
测试命令和输出结果如下 ：
$ adb push Hello.dex /sdcard/
$ adb shell
root@maguro:/ # dalvikvm -cp /sdcard/Hello.dex Hello
Hello, Android!
用python解析Hello.dex后的输出结果
[+] magic: 0x6465780a30333500
[+] checksum: 0x14a36056
[+] signature: 0xc6e6d38bb345f70e58b9b303c2beaf3036a156b2
[+] file_size: 0x000002e4
[+] header_size: 0x00000070
[+] endian_tag: 0x12345678
[+] link_size: 0x00000000
[+] link_off: 0x00000000
[+] map_off: 0x00000244
[+] string_ids_size: 0x0000000e
[+] string_ids_off: 0x00000070
[+] type_ids_size: 0x00000007
[+] type_ids_off: 0x000000a8
[+] proto_ids_size: 0x00000003
[+] proto_ids_off: 0x000000c4
[+] field_ids_size: 0x00000001
[+] field_ids_off: 0x000000e8
[+] method_ids_size: 0x00000004
[+] method_ids_off: 0x000000f0
[+] class_defs_size: 0x00000001
[+] class_defs_off: 0x00000110
[+] data_size: 0x000001b4
[+] data_off: 0x00000130
[+] #DexMapItem 0
u2_type : 0000 kDexTypeHeaderItem
u2_uused : 0000
u4_size : 1
u4_off : 0x0
[+] #DexMapItem 1
u2_type : 0001 kDexTypeStringIdItem
u2_uused : 0000
u4_size : 14
u4_off : 0x70
[+] #DexMapItem 2
u2_type : 0002 kDexTypeTypeIdItem
u2_uused : 0000
u4_size : 7
u4_off : 0xa8
[+] #DexMapItem 3
u2_type : 0003 kDexTypeProtoIdItem
u2_uused : 0000
u4_size : 3
u4_off : 0xc4
[+] #DexMapItem 4
u2_type : 0004 kDexTypeFieldIdItem
u2_uused : 0000
u4_size : 1
u4_off : 0xe8
[+] #DexMapItem 5
u2_type : 0005 kDexTypeMethodIdItem
u2_uused : 0000
u4_size : 4
u4_off : 0xf0
[+] #DexMapItem 6
u2_type : 0006 kDexTypeClassDefItem
u2_uused : 0000
u4_size : 1
u4_off : 0x110
[+] #DexMapItem 7
u2_type : 2001 kDexTypeCodeItem
u2_uused : 0000
u4_size : 2
u4_off : 0x130
[+] #DexMapItem 8
u2_type : 1001 kDexTypeTypeList
u2_uused : 0000
u4_size : 2
u4_off : 0x168
[+] #DexMapItem 9
u2_type : 2002 kDexTypeStringDataItem
u2_uused : 0000
u4_size : 14
u4_off : 0x176
[+] #DexMapItem 10
u2_type : 2003 kDexTypeDebugInfoItem
u2_uused : 0000
u4_size : 2
u4_off : 0x228
[+] #DexMapItem 11
u2_type : 2000 kDexTypeClassDataItem
u2_uused : 0000
u4_size : 1
u4_off : 0x234
[+] #DexMapItem 12
u2_type : 1000 kDexTypeMapList
u2_uused : 0000
u4_size : 1
u4_off : 0x244
[+] #DexString
<init>
Hello, Androie!
Hello.java
LHello;
Ljava/io/PrintStream;
Ljava/lang/Object;
Ljava/lang/String;
Ljava/lang/System;
V
VL
[Ljava/lang/String;
main
out
println
[+] #DexTypeid
u4_descriptoridx0 : LHello;
u4_descriptoridx1 : Ljava/io/PrintStream;
u4_descriptoridx2 : Ljava/lang/Object;
u4_descriptoridx3 : Ljava/lang/String;
u4_descriptoridx4 : Ljava/lang/System;
u4_descriptoridx5 : V
u4_descriptoridx6 : [Ljava/lang/String;
[+] #DexPtotoId
#unit_shorty_id 0 V
u4_descriptoridx0 : Ljava/lang/Object;
u4_descriptoridx0 : 0
#unit_shorty_id 1 VL
u4_descriptoridx1 : Ljava/lang/Object;
u4_descriptoridx1 : 360
DexTypeItemList_Size :1
DexTypeItem _Ljava/lang/String;
#unit_shorty_id 2 VL
u4_descriptoridx2 : Ljava/lang/Object;
u4_descriptoridx2 : 368
DexTypeItemList_Size :1
DexTypeItem _[Ljava/lang/String;
[+] #KDextypeFieldIdItem
Ljava/lang/System;
Ljava/io/PrintStream;
out
[+] #KDextypeMethodIdItem
LHello;
V
<init>
LHello;
VL
main
Ljava/io/PrintStream;
VL
println
Ljava/lang/Object;
V
<init>
[+] #KDextypeClassDefItem 0
classIdx : LHello;
accessflag: 00000001
superclassIdx: Ljava/lang/Object;
interfacesOff: 0
sourceFileIdx: Hello.java
annotationsOff: 0
classDataOff: 564
staticValuesOff: 0
[+] # DexClassData
staticfieldsSize 00
instancefieldsSize 00
directmethodsSize 02
virtualmethodsSize 00
### directmethods 0
[+] MethodIdx: 0x0
[+] accessFlags 0x10001
[+] codeOff 0x130
[+] # DexCode
[+]registersSize 0100
[+]insSize 0100
[+]insSoutsSize 0100
[+]triesSize 0000
[+]debugInfoOff 28020000
[+]insnsSize 04000000
[+]insns [0] 7010
[+]insns [1] 0300
[+]insns [2] 0000
[+]insns [3] 0e00
### directmethods 1
[+] MethodIdx: 0x1
[+] accessFlags 0x9
[+] codeOff 0x148
[+] # DexCode
[+]registersSize 0300
[+]insSize 0100
[+]insSoutsSize 0200
[+]triesSize 0000
[+]debugInfoOff 2d020000
[+]insnsSize 08000000
[+]insns [0] 6200
[+]insns [1] 0000
[+]insns [2] 1a01
[+]insns [3] 0100
[+]insns [4] 6e20
[+]insns [5] 0200
[+]insns [6] 1000
[+]insns [7] 0e00
----------------------------------------
参考：