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jolt.ffi: read-bytes/write-bytes for fixed-length buffer I/O (UTF-8)

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Yogthos 2026-06-22 12:04:19 -04:00
parent 2a64e65a1c
commit f0003151b0
1 changed files with 15 additions and 0 deletions
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15
host/chez/ffi.ss
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@ -65,6 +65,21 @@
(define (ffi-null? ptr) (and (number? ptr) (= (jnum->exact ptr) 0)))
(define ffi-null 0)
;; --- buffer I/O (known length) ----------------------------------------------
;; read n bytes at ptr as a string (UTF-8, falling back to latin1 for invalid
;; sequences) — for a socket recv buffer and similar fixed-length reads.
(define (ffi-read-bytes ptr n)
(let* ((n (jnum->exact n)) (p (jnum->exact ptr)) (bv (make-bytevector n)))
(do ((i 0 (+ i 1))) ((= i n)) (bytevector-u8-set! bv i (foreign-ref 'unsigned-8 p i)))
(guard (e (#t (list->string (map integer->char (bytevector->u8-list bv))))) (utf8->string bv))))
;; write a string's UTF-8 bytes into ptr (no NUL terminator); return the count.
(define (ffi-write-bytes ptr s)
(let* ((bv (string->utf8 (jolt-str-render-one s))) (n (bytevector-length bv)) (p (jnum->exact ptr)))
(do ((i 0 (+ i 1))) ((= i n)) (foreign-set! 'unsigned-8 p i (bytevector-u8-ref bv i)))
n))
(def-var! "jolt.ffi" "read-bytes" ffi-read-bytes)
(def-var! "jolt.ffi" "write-bytes" ffi-write-bytes)
;; --- string / bytevector marshaling ------------------------------------------
;; A C string result already comes back as a jolt string (the `string` foreign
;; type). For a `void*` that points at a NUL-terminated C string, read it here.