Clojure implementation of Bencode, the encoding used by BitTorrent for storing and transmitting loosely structured data.
Add the following dependency to your project.clj file:
[bencode "0.2.4"]
First, import the bencode.core
namespace:
(use '[bencode.core])
At this point, you should be able to use bencode
and bdecode
functions for
encoding and decoding, respectively:
(bencode {:cow "moo" :spam ["info" 32]})
;; -> "d3:cow3:moo4:spaml4:infoi32eee"
(bdecode "d3:cow3:moo4:spaml4:infoi32eee")
;; -> {:cow "moo", :spam ["info" 32]}
```
##### Supported Data Types
According to the Bencoding spec, only _strings_, _integers_, _lists_ and
_dictionaries_ should be supported. Furthermore, only strings can be used as
keys in a dictionary, and the keys must appear in sorted order (sorted as raw
strings, not alphanumerics).
On the Clojure side, _keywords_ are encoded as _strings_, _sets_ and _vectors_
are encoded as _lists_, and all integers - _byte_, _short_, _int_, _long_,
_big integers_ - are encoded as _integers_ with arbitrary size, and decoded to
the smallest type which can hold the number without losing data.
#### Encoding Options
The `bencode` function also accepts an optional map:
````clojure
(bencode "moo" {:raw-str? true})
;; -> #<byte[] [B@53c059f6>
These are the supported encoding options:
:to
- Instance of OutputStream
where the encoding result should be
written to. Default: nil
:raw-str?
- Whether the string being encoded should be returned as a
byte array. This option can only be used if the option :to
is absent.
Default: false
The bdecode
function also accepts an optional map:
(bdecode "d3:cow3:moo4:spaml4:infoi32eee", {:str-keys? true :raw-keys ["spam"]})
;; -> {"cow" "moo", "spam" [#<byte[] [B@74184b3b> 32]}
The input might be either a string, a byte array or an input stream.
These are the supported decoding options:
:str-keys?
- Whether strings should be used as dictionary keys instead of
keywords. Default: false
:raw-keys
- List containing all dictionary keys whose values should be
decoded as raw strings instead of UTF-8-encoded strings. Default: nil
A collection of useful functions for BitTorrent metainfo parsing are available
under the bencode.metainfo.reader
namespace:
(use '[bencode.metainfo.reader])
;; parsing an input stream
(def metainfo (parse-metainfo input-stream))
;; parsing a file given its path
(def metainfo (parse-metainfo-file "/file/path"))
To extract bits of information from this metainfo:
(torrent-name metainfo)
;; -> "my.supercool.torrent"
(public-torrent? metainfo)
;; -> true
(torrent-info-hash-str metainfo)
;; -> "b174c9c090275f858853ba5ea1b01762eaa59f9d"
It's also possible to generate the Magnet link for a metainfo:
(torrent-magnet-link metainfo)
;; -> "magnet:?xt=urn:btih:..."
Please check out the source code for a complete list of the available functions.
It's very easy to create a metainfo file:
(use '[bencode.metainfo.writer])
(def metainfo (create-metainfo :file file-obj
:created-by "You"
:announce-list [["tracker-1"] ["tracker-2"]]
:private? false
:name "optional.torrent.name"
:piece-length-power 7 ;; piece length = 2^7KiB
:n-threads 4 ;; for fast parallel piece hashing
:comment "Some torrent"))
This operation might take several minutes depending on the file size.
To be able to import this file in your favorite BitTorrent client, just bencode
metainfo
to a .torrent file and you're done:
(bencode metainfo {:to file-out-stream})
Copyright (C) Daniel Fernandes Martins
Distributed under the New BSD License. See COPYING for further details.
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