Block diagram
LHA (LHarc, LZH) is a file format used by a popular freeware eponymous archiver, created in 1988 by Haruyasu Yoshizaki. Over the years, many ports and implementations were developed, sporting many extensions to original 1988 LZH.
File format is pretty simple and essentially consists of a stream of records.
This page hosts a formal specification of .lzh file format of LHA (AKA LHarc) by Yoshizaki Haruyasu using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
meta:
id: lzh
application: LHA (AKA LHarc) by Yoshizaki Haruyasu
file-extension: lzh
xref:
justsolve: LHA
pronom: fmt/626
wikidata: Q368782
license: CC0-1.0
imports:
- /common/dos_datetime
endian: le
doc: |
LHA (LHarc, LZH) is a file format used by a popular freeware
eponymous archiver, created in 1988 by Haruyasu Yoshizaki. Over the
years, many ports and implementations were developed, sporting many
extensions to original 1988 LZH.
File format is pretty simple and essentially consists of a stream of
records.
seq:
- id: entries
type: record
repeat: eos
types:
record:
seq:
- id: header_len
type: u1
- id: file_record
type: file_record
if: header_len > 0
file_record:
seq:
- id: header
size: _parent.header_len - 1
type: header
- id: file_uncompr_crc16
type: u2
if: header.header1.lha_level == 0
- id: body
size: header.header1.file_size_compr
header:
seq:
- id: header1
type: header1
doc: >
Level-neutral header, same for all LHA levels. Subsequent
fields order and meaning varies, based on LHA level
specified in this header.
- id: filename_len
type: u1
if: header1.lha_level == 0
- id: filename
type: str
size: filename_len
encoding: ASCII
if: header1.lha_level == 0
- id: file_uncompr_crc16
type: u2
if: header1.lha_level == 2
- id: os
type: u1
if: header1.lha_level == 2
- id: ext_header_size
type: u2
if: header1.lha_level == 2
header1:
seq:
- id: header_checksum
type: u1
- id: method_id
type: str
size: 5
encoding: ASCII
- id: file_size_compr
type: u4
doc: Compressed file size
- id: file_size_uncompr
type: u4
doc: Uncompressed file size
- id: file_timestamp
size: 4
type: dos_datetime
doc: Original file date/time
- id: attr
type: u1
doc: File or directory attribute
- id: lha_level
type: u1