This page hosts a formal specification of .nes file format using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for Ruby generated by Kaitai Struct depends on the Ruby runtime library. You have to install it before you can parse data.
The Ruby runtime library can be installed from RubyGems:
gem install kaitai-structParse a local file and get structure in memory:
data = Ines.from_file("path/to/local/file.nes")
Or parse structure from a string of bytes:
bytes = "\x00\x01\x02..."
data = Ines.new(Kaitai::Struct::Stream.new(bytes))
After that, one can get various attributes from the structure by invoking getter methods like:
data.header # => get header
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
require 'kaitai/struct/struct'
unless Gem::Version.new(Kaitai::Struct::VERSION) >= Gem::Version.new('0.9')
raise "Incompatible Kaitai Struct Ruby API: 0.9 or later is required, but you have #{Kaitai::Struct::VERSION}"
end
##
# @see https://www.nesdev.org/wiki/INES Source
class Ines < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@_raw_header = @_io.read_bytes(16)
_io__raw_header = Kaitai::Struct::Stream.new(@_raw_header)
@header = Header.new(_io__raw_header, self, @_root)
if header.f6.trainer
@trainer = @_io.read_bytes(512)
end
@prg_rom = @_io.read_bytes((header.len_prg_rom * 16384))
@chr_rom = @_io.read_bytes((header.len_chr_rom * 8192))
if header.f7.playchoice10
@playchoice10 = Playchoice10.new(@_io, self, @_root)
end
if !(_io.eof?)
@title = (@_io.read_bytes_full).force_encoding("ASCII")
end
self
end
class Header < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@magic = @_io.read_bytes(4)
raise Kaitai::Struct::ValidationNotEqualError.new([78, 69, 83, 26].pack('C*'), magic, _io, "/types/header/seq/0") if not magic == [78, 69, 83, 26].pack('C*')
@len_prg_rom = @_io.read_u1
@len_chr_rom = @_io.read_u1
@_raw_f6 = @_io.read_bytes(1)
_io__raw_f6 = Kaitai::Struct::Stream.new(@_raw_f6)
@f6 = F6.new(_io__raw_f6, self, @_root)
@_raw_f7 = @_io.read_bytes(1)
_io__raw_f7 = Kaitai::Struct::Stream.new(@_raw_f7)
@f7 = F7.new(_io__raw_f7, self, @_root)
@len_prg_ram = @_io.read_u1
@_raw_f9 = @_io.read_bytes(1)
_io__raw_f9 = Kaitai::Struct::Stream.new(@_raw_f9)
@f9 = F9.new(_io__raw_f9, self, @_root)
@_raw_f10 = @_io.read_bytes(1)
_io__raw_f10 = Kaitai::Struct::Stream.new(@_raw_f10)
@f10 = F10.new(_io__raw_f10, self, @_root)
@reserved = @_io.read_bytes(5)
raise Kaitai::Struct::ValidationNotEqualError.new([0, 0, 0, 0, 0].pack('C*'), reserved, _io, "/types/header/seq/8") if not reserved == [0, 0, 0, 0, 0].pack('C*')
self
end
##
# @see https://www.nesdev.org/wiki/INES#Flags_6 Source
class F6 < Kaitai::Struct::Struct
MIRRORING = {
0 => :mirroring_horizontal,
1 => :mirroring_vertical,
}
I__MIRRORING = MIRRORING.invert
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@lower_mapper = @_io.read_bits_int_be(4)
@four_screen = @_io.read_bits_int_be(1) != 0
@trainer = @_io.read_bits_int_be(1) != 0
@has_battery_ram = @_io.read_bits_int_be(1) != 0
@mirroring = Kaitai::Struct::Stream::resolve_enum(MIRRORING, @_io.read_bits_int_be(1))
self
end
##
# Lower nibble of mapper number
attr_reader :lower_mapper
##
# Ignore mirroring control or above mirroring bit; instead provide four-screen VRAM
attr_reader :four_screen
##
# 512-byte trainer at $7000-$71FF (stored before PRG data)
attr_reader :trainer
##
# If on the cartridge contains battery-backed PRG RAM ($6000-7FFF) or other persistent memory
attr_reader :has_battery_ram
##
# if 0, horizontal arrangement. if 1, vertical arrangement
attr_reader :mirroring
end
##
# @see https://www.nesdev.org/wiki/INES#Flags_7 Source
class F7 < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@upper_mapper = @_io.read_bits_int_be(4)
@format = @_io.read_bits_int_be(2)
@playchoice10 = @_io.read_bits_int_be(1) != 0
@vs_unisystem = @_io.read_bits_int_be(1) != 0
self
end
##
# Upper nibble of mapper number
attr_reader :upper_mapper
##
# If equal to 2, flags 8-15 are in NES 2.0 format
attr_reader :format
##
# Determines if it made for a Nintendo PlayChoice-10 or not
attr_reader :playchoice10
##
# Determines if it is made for a Nintendo VS Unisystem or not
attr_reader :vs_unisystem
end
##
# @see https://www.nesdev.org/wiki/INES#Flags_9 Source
class F9 < Kaitai::Struct::Struct
TV_SYSTEM = {
0 => :tv_system_ntsc,
1 => :tv_system_pal,
}
I__TV_SYSTEM = TV_SYSTEM.invert
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@reserved = @_io.read_bits_int_be(7)
@tv_system = Kaitai::Struct::Stream::resolve_enum(TV_SYSTEM, @_io.read_bits_int_be(1))
self
end
attr_reader :reserved
##
# if 0, NTSC. If 1, PAL.
attr_reader :tv_system
end
##
# @see https://www.nesdev.org/wiki/INES#Flags_10 Source
class F10 < Kaitai::Struct::Struct
TV_SYSTEM = {
0 => :tv_system_ntsc,
1 => :tv_system_dual1,
2 => :tv_system_pal,
3 => :tv_system_dual2,
}
I__TV_SYSTEM = TV_SYSTEM.invert
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@reserved1 = @_io.read_bits_int_be(2)
@bus_conflict = @_io.read_bits_int_be(1) != 0
@prg_ram = @_io.read_bits_int_be(1) != 0
@reserved2 = @_io.read_bits_int_be(2)
@tv_system = Kaitai::Struct::Stream::resolve_enum(TV_SYSTEM, @_io.read_bits_int_be(2))
self
end
attr_reader :reserved1
##
# If 0, no bus conflicts. If 1, bus conflicts.
attr_reader :bus_conflict
##
# If 0, PRG ram is present. If 1, not present.
attr_reader :prg_ram
attr_reader :reserved2
##
# if 0, NTSC. If 2, PAL. If 1 or 3, dual compatible.
attr_reader :tv_system
end
##
# @see https://www.nesdev.org/wiki/Mapper Source
def mapper
return @mapper unless @mapper.nil?
@mapper = (f6.lower_mapper | (f7.upper_mapper << 4))
@mapper
end
attr_reader :magic
##
# Size of PRG ROM in 16 KB units
attr_reader :len_prg_rom
##
# Size of CHR ROM in 8 KB units (Value 0 means the board uses CHR RAM)
attr_reader :len_chr_rom
attr_reader :f6
attr_reader :f7
##
# Size of PRG RAM in 8 KB units (Value 0 infers 8 KB for compatibility; see PRG RAM circuit on nesdev.com)
attr_reader :len_prg_ram
attr_reader :f9
##
# this one is unofficial
attr_reader :f10
attr_reader :reserved
attr_reader :_raw_f6
attr_reader :_raw_f7
attr_reader :_raw_f9
attr_reader :_raw_f10
end
##
# @see https://www.nesdev.org/wiki/PC10_ROM-Images Source
class Playchoice10 < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@inst_rom = @_io.read_bytes(8192)
@prom = Prom.new(@_io, self, @_root)
self
end
class Prom < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@data = @_io.read_bytes(16)
@counter_out = @_io.read_bytes(16)
self
end
attr_reader :data
attr_reader :counter_out
end
attr_reader :inst_rom
attr_reader :prom
end
attr_reader :header
attr_reader :trainer
attr_reader :prg_rom
attr_reader :chr_rom
attr_reader :playchoice10
attr_reader :title
attr_reader :_raw_header
end