Need foreign string method for translate-into-foreign-memory?

[Liam Healy]

On Sun, Oct 6, 2013 at 3:42 AM, Luís Oliveira <loliveira at common-lisp.net> wrote:
> On Sun, Oct 6, 2013 at 12:36 AM, Liam Healy <lnp at healy.washington.dc.us> wrote:
>>> Having the foreign-string-alloc call lisp-string-to-foreign would
>>> cause the string length to be calculated twice. But it indeed seems
>>> like they could both share a helper function at least.
>>
>> Are you sure?
>>
>> ;;; LMH new function
>> (defun length-of-string-as-foreign (string encoding start end null-terminated-p)
>>   (+ (funcall (octet-counter (lookup-mapping *foreign-string-mappings*
>> encoding))
> [...]
>
>> ;;; LMH new version
>> (defun foreign-string-alloc (string &key (encoding *default-foreign-encoding*)
>>                                       (null-terminated-p t) (start 0) end)
> [...]
>>     (lisp-string-to-foreign
>>      string ptr length :start start :end end :encoding encoding)
> [...]
>
>
>> The only duplication of effort is mapping and null-len, which seem
>> like pretty lightweight operations.
>
> This version of foreign-string-alloc calls the octet-counter function
> twice. Once via length-of-string-as-foreign then again via
> lisp-string-to-foreign.
>
> Cheers,
>
> --
> Luís Oliveira
> http://kerno.org/~luis/

Is that important? octect-counter is a slot lookup. I've always
considered slots the equivalent of ordinary variables, so this seems
at least as efficient as the alternatives.


Liam