Re: [Sbcl-help] Question: sb-ext:octets-to-string on alien-value directly

[Stas B. <sta...@gm...>]

Stas Boukarev <sta...@gm...> writes:

> "Dmitry Ivanov" <div...@gm...> writes:
>
>> Hello folks,
>>
>> Is it possible to pass an alien-value directly to the sb-ext:octets-to-string
>> or to another similar function?
>> For example:
>>
>>  (with-alien ((ptr ...)
>>      (sb-ext:octets-to-string (some-routine ptr)
>>        :external-format external-format))))
>>
>> The brute force approach is
>> - call make-array to create an (unsigned-byte 8) vector,
>> - copy the contents of foreign memory pointed by ptr to the vector,
>> - pass the vector to sb-ext:octets-to-string.
>>
>> I believe the built-in FFI mechanics do this "behind the curtain".
> It is possible, but there's no API exposed.
But if you're not afraid of unexported APIs which can change at any
time, you can do:

(sb-alien::c-string-to-string
 (sb-sys:vector-sap (string 'list))
 :ascii 'base-char)
=> 
"LIST"

-- 
With best regards, Stas.