Portability	portable
Stability	experimental
Maintainer	pxqr.sta@gmail.com
Safe Haskell	None

Network.BitTorrent.Core.PeerId

Contents

PeerId
Generation
Encoding
Decoding
- Extra

Description

PeerID represent self assigned peer identificator. Ideally each host in the network should have unique peer id to avoid collisions, therefore for peer ID generation we use good entropy source. (FIX not really) Peer ID is sent in tracker request, sent and received in peer handshakes and used in /distributed hash table/ queries.

Synopsis

PeerId

data PeerId Source

Peer identifier is exactly 20 bytes long bytestring.

Instances

Eq PeerId
Ord PeerId
Show PeerId
IsString PeerId
ToJSON PeerId
FromJSON PeerId
S.Serialize PeerId
URLShow PeerId
Pretty PeerId
BEncode PeerId

Generation

genPeerId :: IO PeerId Source

Here we use Azureus-style encoding with the following args:

HS for the client id.
Version of the package for the version number
UTC time day ++ day time for the random number.

timestamp :: IO BS.ByteString Source

Gives 15 characters long decimal timestamp such that:

6 bytes : first 6 characters from picoseconds obtained with %q.
1 bytes : character . for readability.
9..* bytes: number of whole seconds since the Unix epoch (!)REVERSED.

Can be used both with shadow and azureus style encoding. This format is used to make the ID's readable(for debugging) and more or less random.

entropy :: IO BS.ByteString Source

Gives 15 character long random bytestring. This is more robust method for generation of random part of peer ID than timestamp.

Encoding

azureusStyle Source

Arguments

:: BS.ByteString	2 character client ID, padded with `H`.
-> BS.ByteString	Version number, padded with `X`.
-> BS.ByteString	Random number, padded with '0'.
-> PeerId	Azureus-style encoded peer ID.

Azureus-style encoding have the following layout:

1 byte : -
2 bytes: client id
4 bytes: version number
1 byte : -
12 bytes: random number

shadowStyle Source

Arguments

:: Char	Client ID.
-> BS.ByteString	Version number.
-> BS.ByteString	Random number.
-> PeerId	Shadow style encoded peer ID.

Shadow-style encoding have the following layout:

1 byte : client id.
0-4 bytes: version number. If less than 4 then padded with - char.
15 bytes : random number. If length is less than 15 then padded with '0' char.

Decoding

clientInfo :: PeerId -> ClientInfo Source

Tries to extract meaningful information from peer ID bytes. If peer id uses unknown coding style then client info returned is def.

Extra

byteStringPadded Source

Arguments

:: BS.ByteString	bytestring to be padded.
-> Int	size of result builder.
-> Char	character used for padding.
-> BS.Builder

Pad bytestring so it's becomes exactly request length. Conversion is done like so:

length < size: Complete bytestring by given charaters.
length = size: Output bytestring as is.
length > size: Drop last (length - size) charaters from a given bytestring.

defaultClientId :: BS.ByteString Source

HS - 2 bytes long client identifier.

defaultVersionNumber :: BS.ByteString Source

Gives exactly 4 bytes long version number for any version of the package. Version is taken from .cabal.