[cffi-devel] Re: [Sbcl-devel] encoding of alien c-string once again

[James Bielman]

Juho Snellman <jsnell at iki.fi> writes:

>   * I'm not sure that the interface is quite right. It seems probable
>     that at one point or another somebody will need to use multiple
>     external formats at once (ebcdic for pathnames and latin-1 for a
>     database connection, or something). So we might need to be able to
>     parametrize the external format to be used when defining the
>     types. As a silly example:
>
>     (define-alien-routine strdup (c-string :external-format :latin-1)
>        (str (c-string :external-format :utf-8)))

I agree; this is what the half-finished patch I have adding support
for string encodings to CFFI looks like as well:

(defcfun "strdup" (:string :encoding :latin-1)
  (str (:string :encoding :utf-8)))

>     James, Luis, would something like this be useful for CFFI? Would
>     the proposed interface work for you? Any opinions on the c-string
>     issue mentioned above?

CFFI wants to operate at a lower level than this.  The sort of
interface that would be really useful for us would be versions of
STRING-TO-OCTETS and OCTETS-TO-STRING that operate on SAPs instead of
octet vectors.  IIRC, there are unexported functions in SBCL for doing
this for the various encodings, but nothing exported.

James