先看DexFile定义
http://androidxref.com/6.0.0_r1/xref/art/runtime/dex_file.h
class DexFile {
// Raw header_item.
struct Header {
uint8_t magic_[8];
uint32_t checksum_; // See also location_checksum_
uint8_t signature_[kSha1DigestSize];//20
uint32_t file_size_; // size of entire file
uint32_t header_size_; // offset to start of next section
uint32_t endian_tag_;
uint32_t link_size_; // unused
uint32_t link_off_; // unused
uint32_t map_off_; // unused
uint32_t string_ids_size_; // number of StringIds
uint32_t string_ids_off_; // file offset of StringIds array
uint32_t type_ids_size_; // number of TypeIds, we don't support more than 65535
uint32_t type_ids_off_; // file offset of TypeIds array
uint32_t proto_ids_size_; // number of ProtoIds, we don't support more than 65535
uint32_t proto_ids_off_; // file offset of ProtoIds array
uint32_t field_ids_size_; // number of FieldIds
uint32_t field_ids_off_; // file offset of FieldIds array
uint32_t method_ids_size_; // number of MethodIds
uint32_t method_ids_off_; // file offset of MethodIds array
uint32_t class_defs_size_; // number of ClassDefs
uint32_t class_defs_off_; // file offset of ClassDef array
uint32_t data_size_; // unused
uint32_t data_off_; // unused
};
// Raw string_id_item.
struct StringId {
uint32_t string_data_off_; // offset in bytes from the base address
private:
DISALLOW_COPY_AND_ASSIGN(StringId);
};
// Raw type_id_item.
struct TypeId {
uint32_t descriptor_idx_; // index into string_ids
private:
DISALLOW_COPY_AND_ASSIGN(TypeId);
};
// Raw field_id_item.
struct FieldId {
uint16_t class_idx_; // index into type_ids_ array for defining class
uint16_t type_idx_; // index into type_ids_ array for field type
uint32_t name_idx_; // index into string_ids_ array for field name
private:
DISALLOW_COPY_AND_ASSIGN(FieldId);
};
// Raw method_id_item.
struct MethodId {
uint16_t class_idx_; // index into type_ids_ array for defining class
uint16_t proto_idx_; // index into proto_ids_ array for method prototype
uint32_t name_idx_; // index into string_ids_ array for method name
private:
DISALLOW_COPY_AND_ASSIGN(MethodId);
};
// Raw proto_id_item.
struct ProtoId {
uint32_t shorty_idx_; // index into string_ids array for shorty descriptor
uint16_t return_type_idx_; // index into type_ids array for return type
uint16_t pad_; // padding = 0
uint32_t parameters_off_; // file offset to type_list for parameter types
private:
DISALLOW_COPY_AND_ASSIGN(ProtoId);
};
// Raw class_def_item.
struct ClassDef {
uint16_t class_idx_; // index into type_ids_ array for this class
uint16_t pad1_; // padding = 0
uint32_t access_flags_;
uint16_t superclass_idx_; // index into type_ids_ array for superclass
uint16_t pad2_; // padding = 0
uint32_t interfaces_off_; // file offset to TypeList
uint32_t source_file_idx_; // index into string_ids_ for source file name
uint32_t annotations_off_; // file offset to annotations_directory_item
uint32_t class_data_off_; // file offset to class_data_item
uint32_t static_values_off_; // file offset to EncodedArray
// Returns the valid access flags, that is, Java modifier bits relevant to the ClassDef type
// (class or interface). These are all in the lower 16b and do not contain runtime flags.
uint32_t GetJavaAccessFlags() const {
..........
}
};
// Raw type_item.
struct TypeItem {
uint16_t type_idx_; // index into type_ids section
};
// Raw type_list.
class TypeList {
public:
uint32_t Size() const {
return size_;
}
// Size in bytes of the part of the list that is common.
static constexpr size_t GetHeaderSize() {
return 4U;
}
// Size in bytes of the whole type list including all the stored elements.
static constexpr size_t GetListSize(size_t count) {
return GetHeaderSize() + sizeof(TypeItem) * count;
}
private:
uint32_t size_; // size of the list, in entries
TypeItem list_[1]; // elements of the list
};
// Raw code_item.
struct CodeItem {
uint16_t registers_size_;
uint16_t ins_size_;
uint16_t outs_size_;
uint16_t tries_size_;
uint32_t debug_info_off_; // file offset to debug info stream
uint32_t insns_size_in_code_units_; // size of the insns array, in 2 byte code units
uint16_t insns_[1];
};
dex文件的产生
可以直接从apk文件中解压出来的class.dex文件做分析。
但是为了使dex文件小一点便于分析，我们自己制作个dex文件，步骤如下
//Bleach.java
public class Bleach {
public static final String TAG = "111111111";
public static final String name = "caoming_123456";
public static final int id1 = 0x333333;
private static final int id2 = 0x444444;
public static void main(String[] args) {
add(id1, id2);
}
public static int add(int a, int b) {
int c = a + b;
return c;
}
}
