class.rb

# http://java.sun.com/docs/books/vmspec/2nd-edition/html/ClassFile.doc.html

require_relative 'binformat'

class FieldrefInfo < Binformat
  endian :big

  short :class_index
  short :name_and_type_index
end

class MethodrefInfo < Binformat
  endian :big

  short :class_index
  short :name_and_type_index
end

class InterfaceMethodrefInfo < Binformat
  endian :big

  short :class_index
  short :name_and_type_index
end

class NameAndTypeInfo < Binformat
  endian :big

  short :name_index
  short :descriptor_index
end

class Utf8Info < Binformat
  endian :big

  short :length
  byte :bytes, :length
end

class CpInfo < Binformat
  endian :big

  CONSTANT_Class = 7
  CONSTANT_Fieldref = 9
  CONSTANT_Methodref = 10
  CONSTANT_InterfaceMethodref = 11
  CONSTANT_String = 8
  CONSTANT_Integer = 3
  CONSTANT_Float = 4
  CONSTANT_Long = 5
  CONSTANT_Double = 6
  CONSTANT_NameAndType = 12
  CONSTANT_Utf8 = 1
  CONSTANT_NAMES = {
    7 => 'Class',
    9 => 'Fieldref',
    10 => 'Methodref',
    11 => 'InterfaceMethodref',
    8 => 'String',
    3 => 'Integer',
    4 => 'Float',
    5 => 'Long',
    6 => 'Double',
    12 => 'NameAndType',
    1 => 'Utf8',
  }

  byte :tag
  some {
    $z = $z ? $z+1 : 1
    puts "#$z: #{CONSTANT_NAMES[tag]}"
    case tag
    when CONSTANT_Class
      short :class_info
    when CONSTANT_Fieldref
      struct FieldrefInfo, :fieldref_info
    when CONSTANT_Methodref
      struct MethodrefInfo, :methodref_info
    when CONSTANT_InterfaceMethodref
      struct InterfaceMethodrefInfo, :interfacemethodref_info
    when CONSTANT_String
      short :string_info
    when CONSTANT_Integer
      int :integer_info
    when CONSTANT_Float
      int :float_info
    when CONSTANT_Long
      byte :long_info, 8
    when CONSTANT_Double
      byte :double_info, 8
    when CONSTANT_NameAndType
      struct NameAndTypeInfo, :nameandtype_info
    when CONSTANT_Utf8
      struct Utf8Info, :utf8_info
    else
      raise tag.to_s + ': unknown CpInfo tag'
    end
  }
end

class AttributeInfo < Binformat
  endian :big

  short :attribute_name_index
  int :attribute_length
  byte :info, :attribute_length
end

class FieldInfo < Binformat
  endian :big

  short :access_flags
  short :name_index
  short :descriptor_index
  short :attributes_count
  struct AttributeInfo, :attributes, :attributes_count
end

class MethodInfo < Binformat
  endian :big

  short :access_flags
  short :name_index
  short :descriptor_index
  short :attributes_count
  struct AttributeInfo, :attributes, :attributes_count
end

class ClassFile < Binformat
  endian :big

  byte :magic, 4
  short :minor_version
  short :major_version
  short :constant_pool_count
  struct CpInfo, :constant_pool, proc{ constant_pool_count-1 }
  short :access_flags
  short :this_class
  short :super_class
  short :interfaces_count
  short :interfaces, :interfaces_count
  short :fields_count
  struct FieldInfo, :fields, :fields_count
  short :methods_count
  struct MethodInfo, :methods, :methods_count
  short :attributes_count
  struct AttributeInfo, :attributes, :attributes_count
end

$BINFORMAT_PROVIDE = ClassFile

if $0 == __FILE__
  require 'yaml'
  cf = ClassFile.new
#  p cf.parse(ARGF)
  r = cf.parse(ARGF)
  puts r.to_yaml
  puts 'rest:'
  p ARGF.read

  puts show_binary(r)

  File.open('out', 'w') do |of|
    of.print(cf.dump(r))
  end
end

elf.rb

require 'binformat'

class Phdr < Binformat
  int :type;
  int :offset;
  addr :vaddr;
  addr :paddr;
  int :filesz;
  int :memsz;
  int :flags;
  int :align;
end

class Shdr < Binformat
  int :name
  int :type
  int :flags
  addr :addr
  int :offset
  int :size
  int :link
  int :info
  int :addralign
  int :entsize
end

class ELF < Binformat
  byte :magic, 4
  byte :ident_class
  byte :ident_data
  byte :ident_version
  byte :ident_osabi
  byte :ident_rest, 8
  short :type
  short :machine
  int :version
  addr :entry
  int :phoff
  int :shoff
  int :flags
  short :ehsize
  short :phentsize
  short :phnum
  short :shentsize
  short :shnum
  short :shstrndx

  seek :phoff

  struct Phdr, :phdr, :phnum

  seek :shoff

  struct Shdr, :shdr, :shnum

end

$BINFORMAT_PROVIDE = ELF

if $0 == __FILE__
  require 'yaml'

  cf = ELF.new
#  p cf.parse(ARGF)
  r = cf.parse(ARGF)
  puts r.to_yaml
  puts 'rest:'
  p ARGF.read

#   File.open('out', 'w') do |of|
#     of.print(cf.dump(r))
#   end
end