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> From: Matthew Dempsky <jivera@xxxxxxxxx>
> Tom Lord <lord@xxxxxxx> writes:
> > ** String Conversions
> > ~ t_scm_error scm_extract_string8 (t_uchar * answer,
> > size_t * answer_len,
> > enum uni_encoding_scheme enc,
> > t_scm_arena instance,
> > t_scm_word * str)
> > Normally, convert `str' to the indicated encoding (which must be
> > one of `uni_utf8', `uni_iso8859_*', or `uni_ascii') storing the
> > result in the memory addressed by `answer' and the number of
> > bytes stored in `*answer_len'. Return 0.
> > On input, `*answer_len' should indicate the amount of storage
> > available at the address `answer'. If there is insuffiencient
> > memory available, `*answer_len' will be set to the number of bytes
> > needed and the value `scm_err_too_short' returned.
> In the case that answer doesn't have enough memory allocated to it to
> store the string, what happens to its contents? I would propose that
> the memory contents be undefined to allow implementations that don't
> store strings in a simple vector to be able to write over the memory
> as it goes and later realize it lacks the storage rather than
> requiring an initial pass over the contents.
That's the intention.
> I think there should also be an error raised when the string can't be
> expressed in the requested encoding (I'll leave it up to someone else
> to name this error) and again answer's memory should be undefined.
> (These recommendations apply to all three scm_extract_string*
> functions.)
Correct. SRFI-50 seems still up-in-the-air at the moment but if I
had my druthers, we'd adopt the Pika-style conventions and start
making lists of error code names.
> Somewhat less of an issue (and more current-Pika-implementation
> specific), but why name the t_scm_arena value to instance? A few
> macros (SCM_PROTECT_FRAME and theoretically SCM_LSET) assume the
> arena's name to be arena.
Oh, that's just me being goofy. I prefer the name `arena' for random
reasons -- but in explaining the FFI on this list, `instance' seemed
more communicative (for some random reason).
(In a portable idea, I think that just for hygiene, the
SCM_PROTECT_FRAME and SCM_LSET analogs should accept an explicit
`instance' parameter.)
-t