Typesafe bencode encoders and decoders with semi-automatic derivation.
All releases are published on Maven Central.
To use the library add this to your build.sbt:
libraryDependencies += "io.github.arainko" %% "bencode" % "0.1.0"
Assuming these imports:
import scodec.bits._
import zio.stream.ZStream
import io.github.arainko.bencode._
import io.github.arainko.bencode.syntax._
import io.github.arainko.bencode.derivation.semiauto._Given a torrent file (eg. https://releases.ubuntu.com/20.10/ubuntu-20.10-desktop-amd64.iso.torrent) with a structure like this:
d
8:announce 35:https://torrent.ubuntu.com/announce
13:creation date i1603385085e
13:announce-list
l
l
35:https://torrent.ubuntu.com/announce
e
l
40:https://ipv6.torrent.ubuntu.com/announce
e
e
10:created by 13:mktorrent 1.1
4:info
d
6:length i2942003200e
4:name 30:ubuntu-20.10-desktop-amd64.iso
12:piece length i262144e
6:pieces 224460: <blob>
e
7:comment 29:Ubuntu CD releases.ubuntu.com
e
and a structure of case classes:
final case class Info(length: Long, name: String, pieceLength: Long, pieces: ByteVector)
final case class TorrentFile(
info: Info,
announce: String,
comment: String,
createdBy: String,
creationDate: Long,
announceList: Seq[Seq[String]]
)We can parse the .torrent file almost boilerplate free (always make sure you derive the 'inner' parts of your case class/ADT first!):
implicit val infoDecoder: Decoder[Info] =
deriveDecoder[Info]
.withFieldsRenamed { case "piece length" =>"pieceLength" }
implicit val decoder: Decoder[TorrentFile] = deriveDecoder[TorrentFile].withFieldsRenamed {
case "created by" => "createdBy"
case "creation date" => "creationDate"
case "announce-list" => "announceList"
}
val decoded =
for {
torrentFile <- ZStream.fromResource("ubuntu.torrent").runCollect.map(_.toArray).map(ByteVector.apply)
parsed = Bencode.parse(torrentFile)
decoded = parsed.flatMap(_.cursor.as[TorrentFile])
} yield decoded
// output
Right(
TorrentFile(
info = Info(
length = 2942003200,
name = ubuntu-20.10-desktop-amd64.iso,262144,
pieces = ByteVector(224460 bytes, #-469656818)
),
announce = https://torrent.ubuntu.com/announce,
name = Ubuntu CD releases.ubuntu.com,
createdBy = mktorrent 1.1,
creationDate = 1603385085,
announceList = List(List(https://torrent.ubuntu.com/announce), List(https://ipv6.torrent.ubuntu.com/announce))
)
)This library's design is heavily influenced by the great circe,
uses the just-as-great shapeless for typeclass derivation
and makes use of scodec's ByteVector for binary representation
of bencoded values.