Android Dalvik VM executable (dex): Lua parsing library

Android OS applications executables are typically stored in its own format, optimized for more efficient execution in Dalvik virtual machine.

This format is loosely similar to Java .class file format and generally holds the similar set of data: i.e. classes, methods, fields, annotations, etc.

File extension

dex

KS implementation details

License: Apache-2.0

References

This page hosts a formal specification of Android Dalvik VM executable (dex) using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Lua source code to parse Android Dalvik VM executable (dex)

dex.lua

-- This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
--
-- This file is compatible with Lua 5.3

local class = require("class")
require("kaitaistruct")
local enum = require("enum")
local str_decode = require("string_decode")

require("vlq_base128_le")
-- 
-- Android OS applications executables are typically stored in its own
-- format, optimized for more efficient execution in Dalvik virtual
-- machine.
-- 
-- This format is loosely similar to Java .class file format and
-- generally holds the similar set of data: i.e. classes, methods,
-- fields, annotations, etc.
-- See also: Source (https://source.android.com/devices/tech/dalvik/dex-format)
Dex = class.class(KaitaiStruct)

Dex.ClassAccessFlags = enum.Enum {
  public = 1,
  private = 2,
  protected = 4,
  static = 8,
  final = 16,
  interface = 512,
  abstract = 1024,
  synthetic = 4096,
  annotation = 8192,
  enum = 16384,
}

function Dex:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex:_read()
  self.header = Dex.HeaderItem(self._io, self, self._root)
end

-- 
-- string identifiers list.
-- 
-- These are identifiers for all the strings used by this file, either for
-- internal naming (e.g., type descriptors) or as constant objects referred to by code.
-- 
-- This list must be sorted by string contents, using UTF-16 code point values
-- (not in a locale-sensitive manner), and it must not contain any duplicate entries.
Dex.property.string_ids = {}
function Dex.property.string_ids:get()
  if self._m_string_ids ~= nil then
    return self._m_string_ids
  end

  local _pos = self._io:pos()
  self._io:seek(self.header.string_ids_off)
  self._m_string_ids = {}
  for i = 0, self.header.string_ids_size - 1 do
    self._m_string_ids[i + 1] = Dex.StringIdItem(self._io, self, self._root)
  end
  self._io:seek(_pos)
  return self._m_string_ids
end

-- 
-- method identifiers list.
-- 
-- These are identifiers for all methods referred to by this file,
-- whether defined in the file or not.
-- 
-- This list must be sorted, where the defining type (by type_id index
-- is the major order, method name (by string_id index) is the intermediate
-- order, and method prototype (by proto_id index) is the minor order.
-- 
-- The list must not contain any duplicate entries.
Dex.property.method_ids = {}
function Dex.property.method_ids:get()
  if self._m_method_ids ~= nil then
    return self._m_method_ids
  end

  local _pos = self._io:pos()
  self._io:seek(self.header.method_ids_off)
  self._m_method_ids = {}
  for i = 0, self.header.method_ids_size - 1 do
    self._m_method_ids[i + 1] = Dex.MethodIdItem(self._io, self, self._root)
  end
  self._io:seek(_pos)
  return self._m_method_ids
end

-- 
-- data used in statically linked files.
-- 
-- The format of the data in this section is left unspecified by this document.
-- 
-- This section is empty in unlinked files, and runtime implementations may
-- use it as they see fit.
Dex.property.link_data = {}
function Dex.property.link_data:get()
  if self._m_link_data ~= nil then
    return self._m_link_data
  end

  local _pos = self._io:pos()
  self._io:seek(self.header.link_off)
  self._m_link_data = self._io:read_bytes(self.header.link_size)
  self._io:seek(_pos)
  return self._m_link_data
end

Dex.property.map = {}
function Dex.property.map:get()
  if self._m_map ~= nil then
    return self._m_map
  end

  local _pos = self._io:pos()
  self._io:seek(self.header.map_off)
  self._m_map = Dex.MapList(self._io, self, self._root)
  self._io:seek(_pos)
  return self._m_map
end

-- 
-- class definitions list.
-- 
-- The classes must be ordered such that a given class's superclass and
-- implemented interfaces appear in the list earlier than the referring class.
-- 
-- Furthermore, it is invalid for a definition for the same-named class to
-- appear more than once in the list.
Dex.property.class_defs = {}
function Dex.property.class_defs:get()
  if self._m_class_defs ~= nil then
    return self._m_class_defs
  end

  local _pos = self._io:pos()
  self._io:seek(self.header.class_defs_off)
  self._m_class_defs = {}
  for i = 0, self.header.class_defs_size - 1 do
    self._m_class_defs[i + 1] = Dex.ClassDefItem(self._io, self, self._root)
  end
  self._io:seek(_pos)
  return self._m_class_defs
end

-- 
-- data area, containing all the support data for the tables listed above.
-- 
-- Different items have different alignment requirements, and padding bytes
-- are inserted before each item if necessary to achieve proper alignment.
Dex.property.data = {}
function Dex.property.data:get()
  if self._m_data ~= nil then
    return self._m_data
  end

  local _pos = self._io:pos()
  self._io:seek(self.header.data_off)
  self._m_data = self._io:read_bytes(self.header.data_size)
  self._io:seek(_pos)
  return self._m_data
end

-- 
-- type identifiers list.
-- 
-- These are identifiers for all types (classes, arrays, or primitive types)
-- referred to by this file, whether defined in the file or not.
-- 
-- This list must be sorted by string_id index, and it must not contain any duplicate entries.
Dex.property.type_ids = {}
function Dex.property.type_ids:get()
  if self._m_type_ids ~= nil then
    return self._m_type_ids
  end

  local _pos = self._io:pos()
  self._io:seek(self.header.type_ids_off)
  self._m_type_ids = {}
  for i = 0, self.header.type_ids_size - 1 do
    self._m_type_ids[i + 1] = Dex.TypeIdItem(self._io, self, self._root)
  end
  self._io:seek(_pos)
  return self._m_type_ids
end

-- 
-- method prototype identifiers list.
-- 
-- These are identifiers for all prototypes referred to by this file.
-- 
-- This list must be sorted in return-type (by type_id index) major order,
-- and then by argument list (lexicographic ordering, individual arguments
-- ordered by type_id index). The list must not contain any duplicate entries.
Dex.property.proto_ids = {}
function Dex.property.proto_ids:get()
  if self._m_proto_ids ~= nil then
    return self._m_proto_ids
  end

  local _pos = self._io:pos()
  self._io:seek(self.header.proto_ids_off)
  self._m_proto_ids = {}
  for i = 0, self.header.proto_ids_size - 1 do
    self._m_proto_ids[i + 1] = Dex.ProtoIdItem(self._io, self, self._root)
  end
  self._io:seek(_pos)
  return self._m_proto_ids
end

-- 
-- field identifiers list.
-- 
-- These are identifiers for all fields referred to by this file, whether defined in the file or not.
-- 
-- This list must be sorted, where the defining type (by type_id index)
-- is the major order, field name (by string_id index) is the intermediate
-- order, and type (by type_id index) is the minor order.
-- 
-- The list must not contain any duplicate entries.
Dex.property.field_ids = {}
function Dex.property.field_ids:get()
  if self._m_field_ids ~= nil then
    return self._m_field_ids
  end

  local _pos = self._io:pos()
  self._io:seek(self.header.field_ids_off)
  self._m_field_ids = {}
  for i = 0, self.header.field_ids_size - 1 do
    self._m_field_ids[i + 1] = Dex.FieldIdItem(self._io, self, self._root)
  end
  self._io:seek(_pos)
  return self._m_field_ids
end


Dex.HeaderItem = class.class(KaitaiStruct)

Dex.HeaderItem.EndianConstant = enum.Enum {
  endian_constant = 305419896,
  reverse_endian_constant = 2018915346,
}

function Dex.HeaderItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.HeaderItem:_read()
  self.magic = self._io:read_bytes(4)
  if not(self.magic == "\100\101\120\010") then
    error("not equal, expected " ..  "\100\101\120\010" .. ", but got " .. self.magic)
  end
  self.version_str = str_decode.decode(KaitaiStream.bytes_terminate(self._io:read_bytes(4), 0, false), "ascii")
  self.checksum = self._io:read_u4le()
  self.signature = self._io:read_bytes(20)
  self.file_size = self._io:read_u4le()
  self.header_size = self._io:read_u4le()
  self.endian_tag = Dex.HeaderItem.EndianConstant(self._io:read_u4le())
  self.link_size = self._io:read_u4le()
  self.link_off = self._io:read_u4le()
  self.map_off = self._io:read_u4le()
  self.string_ids_size = self._io:read_u4le()
  self.string_ids_off = self._io:read_u4le()
  self.type_ids_size = self._io:read_u4le()
  self.type_ids_off = self._io:read_u4le()
  self.proto_ids_size = self._io:read_u4le()
  self.proto_ids_off = self._io:read_u4le()
  self.field_ids_size = self._io:read_u4le()
  self.field_ids_off = self._io:read_u4le()
  self.method_ids_size = self._io:read_u4le()
  self.method_ids_off = self._io:read_u4le()
  self.class_defs_size = self._io:read_u4le()
  self.class_defs_off = self._io:read_u4le()
  self.data_size = self._io:read_u4le()
  self.data_off = self._io:read_u4le()
end

-- 
-- adler32 checksum of the rest of the file (everything but magic and this field);
-- used to detect file corruption
-- 
-- SHA-1 signature (hash) of the rest of the file (everything but magic, checksum,
-- and this field); used to uniquely identify files
-- 
-- size of the entire file (including the header), in bytes
-- 
-- size of the header (this entire section), in bytes. This allows for at
-- least a limited amount of backwards/forwards compatibility without
-- invalidating the format.
-- 
-- size of the link section, or 0 if this file isn't statically linked
-- 
-- offset from the start of the file to the link section, or 0 if link_size == 0.
-- The offset, if non-zero, should be to an offset into the link_data section.
-- The format of the data pointed at is left unspecified by this document;
-- this header field (and the previous) are left as hooks for use by runtime implementations.
-- 
-- offset from the start of the file to the map item.
-- The offset, which must be non-zero, should be to an offset into the data
-- section, and the data should be in the format specified by "map_list" below.
-- 
-- count of strings in the string identifiers list
-- 
-- offset from the start of the file to the string identifiers list,
-- or 0 if string_ids_size == 0 (admittedly a strange edge case).
-- The offset, if non-zero, should be to the start of the string_ids section.
-- 
-- count of elements in the type identifiers list, at most 65535
-- 
-- offset from the start of the file to the type identifiers list,
-- or 0 if type_ids_size == 0 (admittedly a strange edge case).
-- The offset, if non-zero, should be to the start of the type_ids section.
-- 
-- count of elements in the prototype identifiers list, at most 65535
-- 
-- offset from the start of the file to the prototype identifiers list,
-- or 0 if proto_ids_size == 0 (admittedly a strange edge case).
-- The offset, if non-zero, should be to the start of the proto_ids section.
-- 
-- count of elements in the field identifiers list
-- 
-- offset from the start of the file to the field identifiers list,
-- or 0 if field_ids_size == 0.
-- The offset, if non-zero, should be to the start of the field_ids section.
-- 
-- count of elements in the method identifiers list
-- 
-- offset from the start of the file to the method identifiers list,
-- or 0 if method_ids_size == 0.
-- The offset, if non-zero, should be to the start of the method_ids section.
-- 
-- count of elements in the class definitions list
-- 
-- offset from the start of the file to the class definitions list,
-- or 0 if class_defs_size == 0 (admittedly a strange edge case).
-- The offset, if non-zero, should be to the start of the class_defs section.
-- 
-- Size of data section in bytes. Must be an even multiple of sizeof(uint).
-- 
-- offset from the start of the file to the start of the data section.

Dex.MapList = class.class(KaitaiStruct)

function Dex.MapList:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.MapList:_read()
  self.size = self._io:read_u4le()
  self.list = {}
  for i = 0, self.size - 1 do
    self.list[i + 1] = Dex.MapItem(self._io, self, self._root)
  end
end


Dex.EncodedValue = class.class(KaitaiStruct)

Dex.EncodedValue.ValueTypeEnum = enum.Enum {
  byte = 0,
  short = 2,
  char = 3,
  int = 4,
  long = 6,
  float = 16,
  double = 17,
  method_type = 21,
  method_handle = 22,
  string = 23,
  type = 24,
  field = 25,
  method = 26,
  enum = 27,
  array = 28,
  annotation = 29,
  null = 30,
  boolean = 31,
}

function Dex.EncodedValue:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.EncodedValue:_read()
  self.value_arg = self._io:read_bits_int_be(3)
  self.value_type = Dex.EncodedValue.ValueTypeEnum(self._io:read_bits_int_be(5))
  self._io:align_to_byte()
  local _on = self.value_type
  if _on == Dex.EncodedValue.ValueTypeEnum.int then
    self.value = self._io:read_s4le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.annotation then
    self.value = Dex.EncodedAnnotation(self._io, self, self._root)
  elseif _on == Dex.EncodedValue.ValueTypeEnum.long then
    self.value = self._io:read_s8le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.method_handle then
    self.value = self._io:read_u4le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.byte then
    self.value = self._io:read_s1()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.array then
    self.value = Dex.EncodedArray(self._io, self, self._root)
  elseif _on == Dex.EncodedValue.ValueTypeEnum.method_type then
    self.value = self._io:read_u4le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.short then
    self.value = self._io:read_s2le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.method then
    self.value = self._io:read_u4le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.double then
    self.value = self._io:read_f8le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.float then
    self.value = self._io:read_f4le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.type then
    self.value = self._io:read_u4le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.enum then
    self.value = self._io:read_u4le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.field then
    self.value = self._io:read_u4le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.string then
    self.value = self._io:read_u4le()
  elseif _on == Dex.EncodedValue.ValueTypeEnum.char then
    self.value = self._io:read_u2le()
  end
end


Dex.CallSiteIdItem = class.class(KaitaiStruct)

function Dex.CallSiteIdItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.CallSiteIdItem:_read()
  self.call_site_off = self._io:read_u4le()
end

-- 
-- offset from the start of the file to call site definition.
-- 
-- The offset should be in the data section, and the data there should
-- be in the format specified by "call_site_item" below.

Dex.MethodIdItem = class.class(KaitaiStruct)

function Dex.MethodIdItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.MethodIdItem:_read()
  self.class_idx = self._io:read_u2le()
  self.proto_idx = self._io:read_u2le()
  self.name_idx = self._io:read_u4le()
end

-- 
-- the definer of this method.
Dex.MethodIdItem.property.class_name = {}
function Dex.MethodIdItem.property.class_name:get()
  if self._m_class_name ~= nil then
    return self._m_class_name
  end

  self._m_class_name = self._root.type_ids[self.class_idx + 1].type_name
  return self._m_class_name
end

-- 
-- the short-form descriptor of the prototype of this method.
Dex.MethodIdItem.property.proto_desc = {}
function Dex.MethodIdItem.property.proto_desc:get()
  if self._m_proto_desc ~= nil then
    return self._m_proto_desc
  end

  self._m_proto_desc = self._root.proto_ids[self.proto_idx + 1].shorty_desc
  return self._m_proto_desc
end

-- 
-- the name of this method.
Dex.MethodIdItem.property.method_name = {}
function Dex.MethodIdItem.property.method_name:get()
  if self._m_method_name ~= nil then
    return self._m_method_name
  end

  self._m_method_name = self._root.string_ids[self.name_idx + 1].value.data
  return self._m_method_name
end

-- 
-- index into the type_ids list for the definer of this method.
-- This must be a class or array type, and not a primitive type.
-- 
-- index into the proto_ids list for the prototype of this method
-- 
-- index into the string_ids list for the name of this method.
-- The string must conform to the syntax for MemberName, defined above.

Dex.TypeItem = class.class(KaitaiStruct)

function Dex.TypeItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.TypeItem:_read()
  self.type_idx = self._io:read_u2le()
end

Dex.TypeItem.property.value = {}
function Dex.TypeItem.property.value:get()
  if self._m_value ~= nil then
    return self._m_value
  end

  self._m_value = self._root.type_ids[self.type_idx + 1].type_name
  return self._m_value
end


Dex.TypeIdItem = class.class(KaitaiStruct)

function Dex.TypeIdItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.TypeIdItem:_read()
  self.descriptor_idx = self._io:read_u4le()
end

Dex.TypeIdItem.property.type_name = {}
function Dex.TypeIdItem.property.type_name:get()
  if self._m_type_name ~= nil then
    return self._m_type_name
  end

  self._m_type_name = self._root.string_ids[self.descriptor_idx + 1].value.data
  return self._m_type_name
end

-- 
-- index into the string_ids list for the descriptor string of this type.
-- The string must conform to the syntax for TypeDescriptor, defined above.

Dex.AnnotationElement = class.class(KaitaiStruct)

function Dex.AnnotationElement:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.AnnotationElement:_read()
  self.name_idx = VlqBase128Le(self._io)
  self.value = Dex.EncodedValue(self._io, self, self._root)
end

-- 
-- element name, represented as an index into the string_ids section.
-- 
-- The string must conform to the syntax for MemberName, defined above.
-- 
-- element value

Dex.EncodedField = class.class(KaitaiStruct)

function Dex.EncodedField:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.EncodedField:_read()
  self.field_idx_diff = VlqBase128Le(self._io)
  self.access_flags = VlqBase128Le(self._io)
end

-- 
-- index into the field_ids list for the identity of this field
-- (includes the name and descriptor), represented as a difference
-- from the index of previous element in the list.
-- 
-- The index of the first element in a list is represented directly.
-- 
-- access flags for the field (public, final, etc.).
-- 
-- See "access_flags Definitions" for details.

Dex.EncodedArrayItem = class.class(KaitaiStruct)

function Dex.EncodedArrayItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.EncodedArrayItem:_read()
  self.value = Dex.EncodedArray(self._io, self, self._root)
end


Dex.ClassDataItem = class.class(KaitaiStruct)

function Dex.ClassDataItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.ClassDataItem:_read()
  self.static_fields_size = VlqBase128Le(self._io)
  self.instance_fields_size = VlqBase128Le(self._io)
  self.direct_methods_size = VlqBase128Le(self._io)
  self.virtual_methods_size = VlqBase128Le(self._io)
  self.static_fields = {}
  for i = 0, self.static_fields_size.value - 1 do
    self.static_fields[i + 1] = Dex.EncodedField(self._io, self, self._root)
  end
  self.instance_fields = {}
  for i = 0, self.instance_fields_size.value - 1 do
    self.instance_fields[i + 1] = Dex.EncodedField(self._io, self, self._root)
  end
  self.direct_methods = {}
  for i = 0, self.direct_methods_size.value - 1 do
    self.direct_methods[i + 1] = Dex.EncodedMethod(self._io, self, self._root)
  end
  self.virtual_methods = {}
  for i = 0, self.virtual_methods_size.value - 1 do
    self.virtual_methods[i + 1] = Dex.EncodedMethod(self._io, self, self._root)
  end
end

-- 
-- the number of static fields defined in this item
-- 
-- the number of instance fields defined in this item
-- 
-- the number of direct methods defined in this item
-- 
-- the number of virtual methods defined in this item
-- 
-- the defined static fields, represented as a sequence of encoded elements.
-- 
-- The fields must be sorted by field_idx in increasing order.
-- 
-- the defined instance fields, represented as a sequence of encoded elements.
-- 
-- The fields must be sorted by field_idx in increasing order.
-- 
-- the defined direct (any of static, private, or constructor) methods,
-- represented as a sequence of encoded elements.
-- 
-- The methods must be sorted by method_idx in increasing order.
-- 
-- the defined virtual (none of static, private, or constructor) methods,
-- represented as a sequence of encoded elements.
-- 
-- This list should not include inherited methods unless overridden by
-- the class that this item represents.
-- 
-- The methods must be sorted by method_idx in increasing order.
-- 
-- The method_idx of a virtual method must not be the same as any direct method.

Dex.FieldIdItem = class.class(KaitaiStruct)

function Dex.FieldIdItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.FieldIdItem:_read()
  self.class_idx = self._io:read_u2le()
  self.type_idx = self._io:read_u2le()
  self.name_idx = self._io:read_u4le()
end

-- 
-- the definer of this field.
Dex.FieldIdItem.property.class_name = {}
function Dex.FieldIdItem.property.class_name:get()
  if self._m_class_name ~= nil then
    return self._m_class_name
  end

  self._m_class_name = self._root.type_ids[self.class_idx + 1].type_name
  return self._m_class_name
end

-- 
-- the type of this field.
Dex.FieldIdItem.property.type_name = {}
function Dex.FieldIdItem.property.type_name:get()
  if self._m_type_name ~= nil then
    return self._m_type_name
  end

  self._m_type_name = self._root.type_ids[self.type_idx + 1].type_name
  return self._m_type_name
end

-- 
-- the name of this field.
Dex.FieldIdItem.property.field_name = {}
function Dex.FieldIdItem.property.field_name:get()
  if self._m_field_name ~= nil then
    return self._m_field_name
  end

  self._m_field_name = self._root.string_ids[self.name_idx + 1].value.data
  return self._m_field_name
end

-- 
-- index into the type_ids list for the definer of this field.
-- This must be a class type, and not an array or primitive type.
-- 
-- index into the type_ids list for the type of this field
-- 
-- index into the string_ids list for the name of this field.
-- The string must conform to the syntax for MemberName, defined above.

Dex.EncodedAnnotation = class.class(KaitaiStruct)

function Dex.EncodedAnnotation:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.EncodedAnnotation:_read()
  self.type_idx = VlqBase128Le(self._io)
  self.size = VlqBase128Le(self._io)
  self.elements = {}
  for i = 0, self.size.value - 1 do
    self.elements[i + 1] = Dex.AnnotationElement(self._io, self, self._root)
  end
end

-- 
-- type of the annotation.
-- 
-- This must be a class (not array or primitive) type.
-- 
-- number of name-value mappings in this annotation
-- 
-- elements of the annotation, represented directly in-line (not as offsets).
-- 
-- Elements must be sorted in increasing order by string_id index.

Dex.ClassDefItem = class.class(KaitaiStruct)

function Dex.ClassDefItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.ClassDefItem:_read()
  self.class_idx = self._io:read_u4le()
  self.access_flags = Dex.ClassAccessFlags(self._io:read_u4le())
  self.superclass_idx = self._io:read_u4le()
  self.interfaces_off = self._io:read_u4le()
  self.source_file_idx = self._io:read_u4le()
  self.annotations_off = self._io:read_u4le()
  self.class_data_off = self._io:read_u4le()
  self.static_values_off = self._io:read_u4le()
end

Dex.ClassDefItem.property.type_name = {}
function Dex.ClassDefItem.property.type_name:get()
  if self._m_type_name ~= nil then
    return self._m_type_name
  end

  self._m_type_name = self._root.type_ids[self.class_idx + 1].type_name
  return self._m_type_name
end

Dex.ClassDefItem.property.class_data = {}
function Dex.ClassDefItem.property.class_data:get()
  if self._m_class_data ~= nil then
    return self._m_class_data
  end

  if self.class_data_off ~= 0 then
    local _pos = self._io:pos()
    self._io:seek(self.class_data_off)
    self._m_class_data = Dex.ClassDataItem(self._io, self, self._root)
    self._io:seek(_pos)
  end
  return self._m_class_data
end

Dex.ClassDefItem.property.static_values = {}
function Dex.ClassDefItem.property.static_values:get()
  if self._m_static_values ~= nil then
    return self._m_static_values
  end

  if self.static_values_off ~= 0 then
    local _pos = self._io:pos()
    self._io:seek(self.static_values_off)
    self._m_static_values = Dex.EncodedArrayItem(self._io, self, self._root)
    self._io:seek(_pos)
  end
  return self._m_static_values
end

-- 
-- index into the type_ids list for this class.
-- 
-- This must be a class type, and not an array or primitive type.
-- 
-- access flags for the class (public, final, etc.).
-- 
-- See "access_flags Definitions" for details.
-- 
-- index into the type_ids list for the superclass,
-- or the constant value NO_INDEX if this class has no superclass
-- (i.e., it is a root class such as Object).
-- 
-- If present, this must be a class type, and not an array or primitive type.
-- 
-- offset from the start of the file to the list of interfaces, or 0 if there are none.
-- 
-- This offset should be in the data section, and the data there should
-- be in the format specified by "type_list" below. Each of the elements
-- of the list must be a class type (not an array or primitive type),
-- and there must not be any duplicates.
-- 
-- index into the string_ids list for the name of the file containing
-- the original source for (at least most of) this class, or the
-- special value NO_INDEX to represent a lack of this information.
-- 
-- The debug_info_item of any given method may override this source file,
-- but the expectation is that most classes will only come from one source file.
-- 
-- offset from the start of the file to the annotations structure for
-- this class, or 0 if there are no annotations on this class.
-- 
-- This offset, if non-zero, should be in the data section, and the data
-- there should be in the format specified by "annotations_directory_item"
-- below,with all items referring to this class as the definer.
-- 
-- offset from the start of the file to the associated class data for this
-- item, or 0 if there is no class data for this class.
-- 
-- (This may be the case, for example, if this class is a marker interface.)
-- 
-- The offset, if non-zero, should be in the data section, and the data
-- there should be in the format specified by "class_data_item" below,
-- with all items referring to this class as the definer.
-- 
-- offset from the start of the file to the list of initial values for
-- static fields, or 0 if there are none (and all static fields are to be
-- initialized with 0 or null).
-- 
-- This offset should be in the data section, and the data there should
-- be in the format specified by "encoded_array_item" below.
-- 
-- The size of the array must be no larger than the number of static fields
-- declared by this class, and the elements correspond to the static fields
-- in the same order as declared in the corresponding field_list.
-- 
-- The type of each array element must match the declared type of its
-- corresponding field.
-- 
-- If there are fewer elements in the array than there are static fields,
-- then the leftover fields are initialized with a type-appropriate 0 or null.

Dex.TypeList = class.class(KaitaiStruct)

function Dex.TypeList:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.TypeList:_read()
  self.size = self._io:read_u4le()
  self.list = {}
  for i = 0, self.size - 1 do
    self.list[i + 1] = Dex.TypeItem(self._io, self, self._root)
  end
end


Dex.StringIdItem = class.class(KaitaiStruct)

function Dex.StringIdItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.StringIdItem:_read()
  self.string_data_off = self._io:read_u4le()
end

Dex.StringIdItem.property.value = {}
function Dex.StringIdItem.property.value:get()
  if self._m_value ~= nil then
    return self._m_value
  end

  local _pos = self._io:pos()
  self._io:seek(self.string_data_off)
  self._m_value = Dex.StringIdItem.StringDataItem(self._io, self, self._root)
  self._io:seek(_pos)
  return self._m_value
end

-- 
-- offset from the start of the file to the string data for this item.
-- The offset should be to a location in the data section, and the data
-- should be in the format specified by "string_data_item" below.
-- There is no alignment requirement for the offset.

Dex.StringIdItem.StringDataItem = class.class(KaitaiStruct)

function Dex.StringIdItem.StringDataItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.StringIdItem.StringDataItem:_read()
  self.utf16_size = VlqBase128Le(self._io)
  self.data = str_decode.decode(self._io:read_bytes(self.utf16_size.value), "ascii")
end


Dex.ProtoIdItem = class.class(KaitaiStruct)

function Dex.ProtoIdItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.ProtoIdItem:_read()
  self.shorty_idx = self._io:read_u4le()
  self.return_type_idx = self._io:read_u4le()
  self.parameters_off = self._io:read_u4le()
end

-- 
-- short-form descriptor string of this prototype, as pointed to by shorty_idx.
Dex.ProtoIdItem.property.shorty_desc = {}
function Dex.ProtoIdItem.property.shorty_desc:get()
  if self._m_shorty_desc ~= nil then
    return self._m_shorty_desc
  end

  self._m_shorty_desc = self._root.string_ids[self.shorty_idx + 1].value.data
  return self._m_shorty_desc
end

-- 
-- list of parameter types for this prototype.
Dex.ProtoIdItem.property.params_types = {}
function Dex.ProtoIdItem.property.params_types:get()
  if self._m_params_types ~= nil then
    return self._m_params_types
  end

  if self.parameters_off ~= 0 then
    local _io = self._root._io
    local _pos = _io:pos()
    _io:seek(self.parameters_off)
    self._m_params_types = Dex.TypeList(_io, self, self._root)
    _io:seek(_pos)
  end
  return self._m_params_types
end

-- 
-- return type of this prototype.
Dex.ProtoIdItem.property.return_type = {}
function Dex.ProtoIdItem.property.return_type:get()
  if self._m_return_type ~= nil then
    return self._m_return_type
  end

  self._m_return_type = self._root.type_ids[self.return_type_idx + 1].type_name
  return self._m_return_type
end

-- 
-- index into the string_ids list for the short-form descriptor string of this prototype.
-- The string must conform to the syntax for ShortyDescriptor, defined above,
-- and must correspond to the return type and parameters of this item.
-- 
-- index into the type_ids list for the return type of this prototype
-- 
-- offset from the start of the file to the list of parameter types for this prototype,
-- or 0 if this prototype has no parameters.
-- This offset, if non-zero, should be in the data section, and the data
-- there should be in the format specified by "type_list" below.
-- Additionally, there should be no reference to the type void in the list.

Dex.EncodedMethod = class.class(KaitaiStruct)

function Dex.EncodedMethod:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.EncodedMethod:_read()
  self.method_idx_diff = VlqBase128Le(self._io)
  self.access_flags = VlqBase128Le(self._io)
  self.code_off = VlqBase128Le(self._io)
end

-- 
-- index into the method_ids list for the identity of this method
-- (includes the name and descriptor), represented as a difference
-- from the index of previous element in the list.
-- 
-- The index of the first element in a list is represented directly.
-- 
-- access flags for the field (public, final, etc.).
-- 
-- See "access_flags Definitions" for details.
-- 
-- offset from the start of the file to the code structure for this method,
-- or 0 if this method is either abstract or native.
-- 
-- The offset should be to a location in the data section.
-- 
-- The format of the data is specified by "code_item" below.

Dex.MapItem = class.class(KaitaiStruct)

Dex.MapItem.MapItemType = enum.Enum {
  header_item = 0,
  string_id_item = 1,
  type_id_item = 2,
  proto_id_item = 3,
  field_id_item = 4,
  method_id_item = 5,
  class_def_item = 6,
  call_site_id_item = 7,
  method_handle_item = 8,
  map_list = 4096,
  type_list = 4097,
  annotation_set_ref_list = 4098,
  annotation_set_item = 4099,
  class_data_item = 8192,
  code_item = 8193,
  string_data_item = 8194,
  debug_info_item = 8195,
  annotation_item = 8196,
  encoded_array_item = 8197,
  annotations_directory_item = 8198,
}

function Dex.MapItem:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.MapItem:_read()
  self.type = Dex.MapItem.MapItemType(self._io:read_u2le())
  self.unused = self._io:read_u2le()
  self.size = self._io:read_u4le()
  self.offset = self._io:read_u4le()
end

-- 
-- type of the items; see table below
-- 
-- (unused)
-- 
-- count of the number of items to be found at the indicated offset
-- 
-- offset from the start of the file to the items in question

Dex.EncodedArray = class.class(KaitaiStruct)

function Dex.EncodedArray:_init(io, parent, root)
  KaitaiStruct._init(self, io)
  self._parent = parent
  self._root = root or self
  self:_read()
end

function Dex.EncodedArray:_read()
  self.size = VlqBase128Le(self._io)
  self.values = {}
  for i = 0, self.size.value - 1 do
    self.values[i + 1] = Dex.EncodedValue(self._io, self, self._root)
  end
end