Passing lisp vector to foreign code

So, I have a binary stream class that collects bytes into a buffer
represented by a vector with a fill pointer. I want to take this buffer and
send it to a C function, which stores it in a "database". Later, I want to
retrieve this data via another binary stream class (we're experimenting with
CL-STORE). Using the lw ffi, how do I set this up? It seems from the docs
that I need to make a copy of the buffer in static space prior to sending it
to C; is that correct? What should the ffi function declarations look like?
Currently, I have:

(fli:define-foreign-function
    (put-bytes "put_bytes" :source)
    ((bytes (:c-array (:unsigned :char)))
     (len :int))
  :result-type :void
  :calling-convention :cdecl)

(fli:define-foreign-function
    (get-bytes "get_bytes" :source)
    ((nbytes (:pointer (:int))))
  :result-type (:c-array (:unsigned :char))
  :calling-convention :cdecl)

But, passing a Lisp vector to PUT-BYTES yields a type error:

  Expecting type (:foreign-array (:UNSIGNED :CHAR) (0)) (got #(76 ...))

so clearly I'm doing something wrong. Thanks for the help.

David E. Young
Bloodhound Software, Inc.

For wisdom is more precious than rubies,
and nothing you desire can compare with her.
  -- Prov. 8:11

"But all the world understands my language."
  -- Franz Josef Haydn (1732 - 1809)


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