simon/jolt
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

jolt.ffi: read-array/write-array for binary-faithful buffer I/O

Browse source 
read-bytes/write-bytes go through UTF-8 (with a latin1 fallback), which mangles
arbitrary binary — gzip payloads, TLS records, any non-text body. An HTTP client
moving bytes between jolt byte-arrays and foreign socket/zlib/OpenSSL buffers
needs byte-exact transfer. read-array returns a fresh byte-array of n bytes from
foreign memory; write-array copies a byte-array's bytes into a pointer. Test
covers a round-trip preserving high bytes (200, 255).
This commit is contained in:
Yogthos 2026-06-22 13:11:08 -04:00
parent 8c6623503f
commit c5e1e0544a
2 changed files with 30 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

17
host/chez/ffi.ss
View file

@ -80,6 +80,23 @@
(def-var! "jolt.ffi" "read-bytes" ffi-read-bytes)
(def-var! "jolt.ffi" "write-bytes" ffi-write-bytes)
;; --- byte-array buffer I/O (binary-faithful) --------------------------------
;; Move raw bytes between a jolt byte-array (jolt-array kind 'byte) and foreign
;; memory, byte-exact (no UTF-8 / latin1 decode) — for socket recv/send and the
;; zlib / OpenSSL buffers an HTTP client passes through. read-array returns a
;; fresh byte-array of n bytes; write-array copies a byte-array's bytes into ptr
;; and returns the count.
(define (ffi-read-array ptr n)
(let* ((n (jnum->exact n)) (p (jnum->exact ptr)) (v (make-vector n 0)))
(do ((i 0 (+ i 1))) ((= i n)) (vector-set! v i (foreign-ref 'unsigned-8 p i)))
(make-jolt-array v 'byte)))
(define (ffi-write-array ptr arr)
(let* ((v (jolt-array-vec arr)) (n (vector-length v)) (p (jnum->exact ptr)))
(do ((i 0 (+ i 1))) ((= i n)) (foreign-set! 'unsigned-8 p i (bitwise-and (exact (vector-ref v i)) #xff)))
n))
(def-var! "jolt.ffi" "read-array" ffi-read-array)
(def-var! "jolt.ffi" "write-array" ffi-write-array)
;; --- 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.