Bencode Library

Bencode (pronounced like B encode) is the encoding used by the peer-to-peer file sharing system BitTorrent for storing and transmitting loosely structured data -- Wikipedia

Features

1. Encode Strings, Longs, Lists, Dictionaries in Bencode
2. Decode byte streams to Bencode Objects
3. Read .torrent files and extract its fields

Examples

Creating Bencode Object

scala> import venkatesh1729.bencoding._
import venkatesh1729.bencoding._

scala> val str: String = "Hello World!"
str: String = Hello World!

scala> val bStr: BString = BString(str.getBytes:_*)
bStr: venkatesh1729.bencoding.BString = Hello World!

scala> val bLong: BLong = BLong(42)
bLong: venkatesh1729.bencoding.BLong = 42

scala> val bList: BList = BList(bStr, bLong)
bList: venkatesh1729.bencoding.BList = [Hello World!, 42]

scala> val bDict: BDict = BDict(Map(bStr -> bLong))
bDict: venkatesh1729.bencoding.BDict = {Hello World!:42}

Encoding Bencode Objects

scala> StringEncoder.encode(bStr)
res5: Seq[Byte] = ArrayBuffer(49, 50, 58, 72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100, 33)

scala> LongEncoder.encode(bLong)
res6: Seq[Byte] = WrappedArray(105, 52, 50, 101)

scala> ListEncoder.encode(bList)
res7: Seq[Byte] = List(108, 49, 50, 58, 72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100, 33, 105, 52, 50, 101, 101)

scala> DictEncoder.encode(bDict)
res8: Seq[Byte] = List(100, 49, 50, 58, 72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100, 33, 105, 52, 50, 101, 101)

Decoding Byte Streams

scala> BParser.parseBObject(StringEncoder.encode(bStr))
res0: Option[venkatesh1729.bencoding.BObject] = Some(Hello World!)

scala> BParser.parseBObject(LongEncoder.encode(bLong))
res1: Option[venkatesh1729.bencoding.BObject] = Some(BLong(42))

scala> BParser.parseBObject(ListEncoder.encode(bList))
res2: Option[venkatesh1729.bencoding.BObject] = Some(BList(List(Hello World!, BLong(42))))

scala> BParser.parseBObject(DictEncoder.encode(bDict))
res3: Option[venkatesh1729.bencoding.BObject] = Some(BDict(Map(Hello World! -> BLong(42))))

Parsing Torrent File

scala> val tObj = TorrentParser.parseTorrentFile("/Users/venkatesh/Desktop/ubuntu-16.04-desktop-amd64.iso.torrent")
tObj: Either[Exception,venkatesh1729.bencoding.TorrentObject]

scala> tObj.right.get.announce
res9: String = http://torrent.ubuntu.com:6969/announce

scala> tObj.right.get.announceList
res10: Option[Seq[Seq[String]]] = Some(List(List(http://torrent.ubuntu.com:6969/announce), List(http://ipv6.torrent.ubuntu.com:6969/announce)))

scala> tObj.right.get.comment
res11: Option[String] = Some(Ubuntu CD releases.ubuntu.com)

scala> tObj.right.get.info.name
res12: String = ubuntu-16.04-desktop-amd64.iso

Note

Although Scala comes with powerful out of the box parser combinators these shouldn't be used for heavy lifting parsing. You might want to look at Parboiled and fastparse. But It will be good exercise to implement with bencoding while learning Scala's parser combinators.