Reading/writing null-terminated strings from socket

Question

I need to handle C style ('0円' delimited) strings from/to a socket and came up with this as a first attempt:

#lang racket
(require racket/tcp)
(define (read-c-str inp)
 (define (read-to-zero acc)
 (define b (read-byte inp))
 (cond 
 [(equal? b 0) (bytes->string/utf-8 (apply bytes (reverse acc)))]
 [else (read-to-zero (cons b acc))]))
 (read-to-zero null))
(define (write-c-str val p)
 (write-bytes (bytes-append (string->bytes/utf-8 val) (bytes 0)) p)
 (flush-output p))

Writing is pretty simple, but I have the feeling I'm missing a more simple way to handle the accumulator there, and mainly looking for feedback on read-c-str. I'm suspicious of having to reverse, making me think there is a better way.

Here was my second attempt which I'm not convinced is a better way:

(define (blist->string blist)
 (bytes->string/utf-8 (foldr (lambda (inb l) (bytes-append l (bytes inb))) #"" blist)))
(define (read-c-str inp)
 (define (read-to-zero acc)
 (define b (read-byte inp))
 (if (equal? b 0)
 (blist->string acc)
 (read-to-zero (cons b acc))))
 (read-to-zero null))

Answer 1

I would accumulate bytes instead of integers.

(define (read-c-str inp)
 (define (read-to-zero acc)
 (define b (read-byte inp))
 (if (equal? b 0)
 (blist->string acc)
 (read-to-zero (bytes-append acc (bytes b)))))
 (read-to-zero #""))

And change blist->string accordingly.

Edit: in this case blist->string will become just bytes->string/utf-8 .

• user54495: can you please point out where specifically I'm using integers? this code appears to be the same, just moved around. edit: nevermind, I see..
• user54495: actually, looking at this again. I'm really not sure. Can you please specify where exactly I'm using an integer?
• Danil Gaponov: You use bytes to convert from number to byte string. And read-byte actually returns numeric representation of the byte read. Try running the following code: (let ([ip (open-input-string "a")])(read-byte ip)) It will return 97, a number. Not a byte string #"a"