Iūdex :
Basic Archive (BARC)
The Iūdex BARC container format supports efficient block storage of raw downloaded or post-processed content. The format was inspired by Heritrix ARC and WARC, but offers several unique features/advantages:
- Concurrent and random-access reads by byte offset (external index).
- Single-writer sessions safe with concurrent reads.
- Per-record GZip compression (headers + body payload).
- Efficient random access channel IO.
- Minimal dependencies for read/write access.
BARC Format
A Human/machine readable header used for first record (offset zero) and each subsequent record:
Magic rlength tt meta rqst resp
BARC1 FFFFFFFF HC FFFF FFFF FFFF(CRLF)
CRLF
All lengths are in hexadecimal bytes, zero-padded and fixed width. The header itself is 36 bytes long
| Component | Description |
|---|---|
| rlength | Length of record in hexadecimal bytes (not including header). |
| tt | Type and compression bytes (see below). |
| meta | Length of meta header block in hexadecimal bytes |
| rqst | Length of request header block in hexadecimal bytes |
| resp | Length of response header block in hexadecimal bytes |
Types
The following record types are currently defined:
| Type | Description |
|---|---|
| R | Replaced (or never completed) record. Most consumers will want to ignore these records. |
| H | HTML or other raw (web downloaded) content. For example, downloaded images would be suitable included as H values. |
| D | A Delete record containing meta headers, but no body. |
Compression mode
The following compression modes are currently defined:
| Mode | Description |
|---|---|
| C | Gzip compressed |
| P | Plain (uncompressed) |
iudex-barc utility
A. Show Record(s)
iudex-barc show barc/000000.barc
iudex-barc show -mqr -o 0xde411 barc/000015.barc
- From BARC file (all or by record offset)
- Decompresses compressed records
(stored in db as integer, so use base-10 offset)
B. HTTP fetch
iudex-http-record [-z] [-t] url outfile
- Append or Truncate existing file
- Compress or not
- Display instead of write?
C. Copy/Concatenate record to file
iudex-barc [-zt] copy infile outfile
- Compress target or not
(last file implicit write)
Human-readable to/from BARC
Format:
-BARC1 H
=META=
meta_header_1: value
meta_header_2: value
=RQST=
Request-Line: GET /foo/bar.html
=RESP=
Status-Line: HTTP/1.1 200 OK
=BODY=
<html>
...
Other records
Sample DELETE:
-BARC1 D
=META=
url: http://foobar/framis
uhash: 98ASDz798a782hasfd79jbz
-
From Wikipedia: BARC-LARC-XV-2.jpeg (public domain) ↩
