Block diagram
ISO9660 is standard filesystem used on read-only optical discs (mostly CD-ROM). The standard was based on earlier High Sierra Format (HSF), proposed for CD-ROMs in 1985, and, after several revisions, it was accepted as ISO9960:1998.
The format emphasizes portability (thus having pretty minimal features and very conservative file names standards) and sequential access (which favors disc devices with relatively slow rotation speed).
This page hosts a formal specification of ISO9660 CD filesystem using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
meta:
id: iso9660
title: ISO9660 CD filesystem
file-extension: iso
xref:
justsolve: ISO_9660
loc: fdd000348
pronom: fmt/468
wikidata: Q815645
license: CC0-1.0
doc: |
ISO9660 is standard filesystem used on read-only optical discs
(mostly CD-ROM). The standard was based on earlier High Sierra
Format (HSF), proposed for CD-ROMs in 1985, and, after several
revisions, it was accepted as ISO9960:1998.
The format emphasizes portability (thus having pretty minimal
features and very conservative file names standards) and sequential
access (which favors disc devices with relatively slow rotation
speed).
types:
vol_desc:
seq:
- id: type
type: u1
- id: magic
contents: "CD001"
- id: version
type: u1
- id: vol_desc_boot_record
type: vol_desc_boot_record
if: type == 0
- id: vol_desc_primary
type: vol_desc_primary
if: type == 1
vol_desc_boot_record:
seq:
- id: boot_system_id
type: str
size: 32
encoding: UTF-8
- id: boot_id
type: str
size: 32
encoding: UTF-8
vol_desc_primary:
doc-ref: 'https://wiki.osdev.org/ISO_9660#The_Primary_Volume_Descriptor'
seq:
- id: unused1
contents: [0]
- id: system_id
type: str
size: 32
encoding: UTF-8
- id: volume_id
type: str
size: 32
encoding: UTF-8
- id: unused2
contents: [0, 0, 0, 0, 0, 0, 0, 0]
- id: vol_space_size
type: u4bi
- id: unused3
contents: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
- id: vol_set_size
type: u2bi
- id: vol_seq_num
type: u2bi
- id: logical_block_size
type: u2bi
- id: path_table_size
type: u4bi
- id: lba_path_table_le
type: u4le
- id: lba_opt_path_table_le
type: u4le
- id: lba_path_table_be
type: u4be
- id: lba_opt_path_table_be
type: u4be
- id: root_dir
type: dir_entry
size: 34
- id: vol_set_id
type: str
size: 128
encoding: UTF-8
- id: publisher_id
type: str
size: 128
encoding: UTF-8
- id: data_preparer_id
type: str
size: 128
encoding: UTF-8
- id: application_id
type: str
size: 128
encoding: UTF-8
- id: copyright_file_id
type: str
size: 38
encoding: UTF-8
- id: abstract_file_id
type: str
size: 36
encoding: UTF-8
- id: bibliographic_file_id
type: str
size: 37
encoding: UTF-8
- id: vol_create_datetime
type: dec_datetime
- id: vol_mod_datetime
type: dec_datetime
- id: vol_expire_datetime
type: dec_datetime
- id: vol_effective_datetime
type: dec_datetime
- id: file_structure_version
type: u1
- id: unused4
type: u1
- id: application_area
size: 512
instances:
path_table:
pos: lba_path_table_le * _root.sector_size
size: path_table_size.le
type: path_table_le
dir_entries:
seq:
- id: entries
type: dir_entry
repeat: until
repeat-until: _.len == 0
dir_entry:
seq:
- id: len
type: u1
- id: body
type: dir_entry_body
size: len - 1
if: len > 0
dir_entry_body:
seq:
- id: len_ext_attr_rec
type: u1
- id: lba_extent
type: u4bi
- id: size_extent
type: u4bi
- id: datetime
type: datetime
- id: file_flags
type: u1
- id: file_unit_size
type: u1
- id: interleave_gap_size
type: u1
- id: vol_seq_num
type: u2bi
- id: len_file_name
type: u1
- id: file_name
type: str
encoding: UTF-8
size: len_file_name
- id: padding
type: u1
if: len_file_name % 2 == 0
- id: rest
size-eos: true
instances:
extent_as_dir:
io: _root._io
pos: lba_extent.le * _root.sector_size
size: size_extent.le
type: dir_entries
if: file_flags & 2 != 0
extent_as_file:
io: _root._io
pos: lba_extent.le * _root.sector_size
size: size_extent.le
if: file_flags & 2 == 0
## AKA "Path Table Entry"
path_table_le:
doc-ref: 'https://wiki.osdev.org/ISO_9660#The_Path_Table'
seq:
- id: entries
type: path_table_entry_le
repeat: eos
path_table_entry_le:
seq:
- id: len_dir_name
type: u1
- id: len_ext_attr_rec
type: u1
- id: lba_extent
type: u4le
- id: parent_dir_idx
type: u2le
- id: dir_name
type: str
encoding: UTF-8
size: len_dir_name
- id: padding
type: u1
if: len_dir_name % 2 == 1
datetime:
seq:
- id: year
type: u1
- id: month
type: u1
- id: day
type: u1
- id: hour
type: u1
- id: minute
type: u1
- id: sec
type: u1
- id: timezone
type: u1
dec_datetime:
doc-ref: 'https://wiki.osdev.org/ISO_9660#Date.2Ftime_format'
seq:
- id: year
type: str
size: 4
encoding: ASCII
- id: month
type: str
size: 2
encoding: ASCII
- id: day
type: str
size: 2
encoding: ASCII
- id: hour
type: str
size: 2
encoding: ASCII
- id: minute
type: str
size: 2
encoding: ASCII
- id: sec
type: str
size: 2
encoding: ASCII
- id: sec_hundreds
type: str
size: 2
encoding: ASCII
- id: timezone
type: u1
u2bi:
seq:
- id: le
type: u2le
- id: be
type: u2be
u4bi:
seq:
- id: le
type: u4le
- id: be
type: u4be
instances:
sector_size:
value: 2048
primary_vol_desc:
pos: 0x010 * sector_size
type: vol_desc