Scheme: Data serializing, efficient [and functional]

Question

I'm serializing data which may be an integer, an object (list) with other nested objects, and trying to make a choice as to what approach to be using. Of two, the first one is to create bytevectors recursively and copy them in the calling functions to a larger single bytevector; the second one is to use some kind of the stream I could write to. Eventually, notwithstanding the choice, I would be able to use the resulting binary array in any further processing which may happen to occur, e. g. I would compress the output data and send it via network or just write some parts of it to a file.

I'd like to stay functional enough (or completely) yet implementing the fast serializer. I'm using Racket, though any other Scheme implementation will also do.

Thank you.

UPDATE:

Following are the examples I've added after I found a solution so that users save some time searching the way as to how to write data :]

write-byte and write-bytes are of particular use when you need to write octets.

> (bytes? (with-output-to-bytes (lambda () (write-byte 42))))
#t
> (bytevector? (with-output-to-bytes (lambda () (write-byte 42))))
#t
> (bytevector->u8-list (with-output-to-bytes (lambda () (write-byte 42))))
{42}
> (bytes->list (with-output-to-bytes (lambda () (write-byte 42) (write-bytes (integer->integer-bytes #x101CA75 4 #f #t)))))
(42 1 1 202 117)

Answer 1

Probably open-bytevector-output-port is what I'm looking for:

#lang scheme

(require rnrs/bytevectors-6)
(require rnrs/io/ports-6)

(define-values (oup ext-proc) (open-bytevector-output-port))
(write 4 oup)
(write 2 oup)
(ext-proc)
(make-bytevector 3 1)

Result:

Добро пожаловать в DrScheme, версия 4.2.5 [3m].
Язык: scheme; memory limit: 128 MB.
#"42"
#"\1\1\1"
> 

Answer 2

You can use just write to write the data to a port. You can do that with all values, as a list that holds everything. It might need minor tweaking in case you have issues like cyclic data, where setting print-graph to #t will deal with it fine. And if you want the output to go to a byte string, then you can use open-output-bytes, or the convenient with-output-to-bytes function:

(with-output-to-bytes (lambda () (write (list value1 value2 value3))))

This is not going to be as compact as a binary representation -- but if you plan on compressing the output anyway, it doesn't matter much.