Subject: bug#45816: (ice-9 suspendable-ports):get-bytevector-some! is broken

From: d4ryus <[email-masked]>
Date: Tue, 12 Jan 2021 15:19:05 +0100

hi,

(ice-9 suspendable-ports):get-bytevector-some! calls bytevector-copy!
with transfer-size (which is a number) as third argument:

  ...
  (define (get-bytevector-some! port bv start count)
    (if (zero? count)
        0
        (call-with-values (lambda () (fill-input port 1 'binary))
          (lambda (buf cur buffered)
            (if (zero? buffered)
                (begin
                  (set-port-buffer-has-eof?! buf #f)
                  the-eof-object)
                (let ((transfer-size (min count buffered)))
                  (bytevector-copy! (port-buffer-bytevector buf) cur
                                    transfer-size start buffered)
                  (set-port-buffer-cur! buf (+ cur transfer-size))
                  transfer-size))))))
  ...

The third argument to bytevector-copy! must be the target bytevector,
from the doc:

  Scheme Procedure: bytevector-copy! source source-start target target-start len

    Copy len bytes from source into target, starting reading from
    source-start (a positive index within source) and start writing at
    target-start. It is permitted for the source and target regions to
    overlap.

I think the correct call is:

  (bytevector-copy! (port-buffer-bytevector buf) cur
                    bv start transfer-size)

A potentional fix is attached.

If you need any additional information, please let me know.

-  d4ryus
diff --git a/module/ice-9/suspendable-ports.scm b/module/ice-9/suspendable-ports.scm
index f5f005cca..a823f1d37 100644
--- a/module/ice-9/suspendable-ports.scm
+++ b/module/ice-9/suspendable-ports.scm
@@ -338,7 +338,7 @@
                 the-eof-object)
               (let ((transfer-size (min count buffered)))
                 (bytevector-copy! (port-buffer-bytevector buf) cur
-                                  transfer-size start buffered)
+                                  bv start transfer-size)
                 (set-port-buffer-cur! buf (+ cur transfer-size))
                 transfer-size))))))