suzanne.soy/racket
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

fix length-specifying form of _bytes to include room for nul

Browse Source
This commit is contained in:
Matthew Flatt 2015-07-14 18:07:38 +02:00
parent bfc9eb8d62
commit ec6c88442d
2 changed files with 11 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
pkgs/racket-doc/scribblings/foreign/types.scrbl
View File

@ -1023,13 +1023,11 @@ Racket vectors instead of lists.}
(_bytes o len-expr)]]{
A @tech{custom function type} that can be used by itself as a simple
type for a byte string as a C pointer. Alternatively, the second form
is for a pointer return value, where the size should be explicitly
specified.
There is no need for other modes analogous to those of @racket[_ptr]:
input or input/output would be just like @racket[_bytes], since the
string carries its size information.}
type for a byte string as a C pointer. Coercion of a C pointer to
simply @racket[_bytes] (without a specified length) requires that the pointer
refers to a nul-terminated byte string. When the length-specifying form is used
for a function argument, a byte string is allocated with the given
length, including an extra byte for the nul terminator.}
@; ------------------------------------------------------------

8
racket/collects/ffi/unsafe.rkt
View File

@ -1046,8 +1046,12 @@
(provide (rename-out [_bytes* _bytes]))
(define-fun-syntax _bytes*
(syntax-id-rules (o)
[(_ o n) (type: _pointer
pre: (make-sized-byte-string (malloc n) n)
[(_ o n) (type: _gcpointer
pre: (let ([bstr (make-sized-byte-string (malloc (add1 n)) n)])
;; Ensure a null terminator, so that the result is
;; compatible with `_bytes`:
(ptr-set! bstr _byte n 0)
bstr)
;; post is needed when this is used as a function output type
post: (x => (make-sized-byte-string x n)))]
[(_ . xs) (_bytes . xs)]