This library implements Bencode, "the encoding used by the peer-to-peer file sharing system BitTorrent for storing and transmitting loosely structured data." Quote from Wikipedia.

2References🔗 i

Bencode is defined as part of the BitTorrent specifications. Useful references include:

3Representation of Terms🔗 i

Bencode terms are represented as Racket data structures as follows:

Bencode lists map to Racket lists
Bencode dictionaries map to Racket equal? -hashtables
Bencode integers map to Racket integers
Bencode strings map to Racket byte-vectors (bytes )

In particular, Racket’s null value is the representation of the empty Bencode list.

4What to require🔗 i

All the functionality below can be accessed with a single require :

(require bencode-codec ) package: bencode-codec

4.1Reading Bencoded data🔗 i

procedure
( bencode-read p)→(or/c any?eof-object? )
p:input-port?

Reads and returns a single Bencoded term from the given input-port, or returns eof if the end-of-file is reached before any other data appears on the input-port. An error is signalled if a syntax error or unexpected end-of-file is detected.

If a Bencoded string (Racket bytes) value appears on the input-port and has length in excess of bencode-bytes-limit ’s current value, an error is signalled.

procedure
( bencode-read-to-end p)→list?
p:input-port?

Reads and returns as many Bencoded terms as are available on the given input port. Once end-of-file is reached, returns the terms as a list in the order they were read from the port. Errors are otherwise signalled as for bencode-read .

procedure
( bytes->bencode bs)→list?
bs:bytes?

As bencode-read-to-end , but takes input from the supplied byte-vector instead of from an input-port.

procedure
( bencode-bytes-limit )→integer?
(bencode-bytes-limit new-limit)→void?
new-limit:integer?

A parameter. Retrieves or sets the current limit on strings read by any of the other Bencode-reading functions defined in this library.

4.2Writing Bencoded data🔗 i

procedure
( bencode-write termp)→void?
term:any?
p:output-port?

Writes a single term (which must be a Racket datum as specified in Representation of Terms) to the given output-port.

procedure
( bencode->bytes terms)→bytes?
terms:list?

Returns a byte-vector containing a Bencoded representation of the given list of terms, in the order they appear in the list. Note that it encodes a list of terms, not a single term, and so it is roughly an inverse of bytes->bencode .

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