Re: Passing scalars to C functions

Josef Moellers wrote:
> Reinhard Pagitsch wrote:
>> Josef Moellers wrote:
>>  
>>> Hi,
>>>
>>> I'm fairly new to the XS business. I have managed to get the skeleton 
>>> up (h2xs) and have also managed to write short functions that have 
>>> ints as arguments and return strings, but I'd like to pass a full 
>>> Perl scalar (my $cdb = pack('C*', 0x12, 0, 0, 0, 128, 0);) and 
>>> retrieve the length (6) and the bytes themselves in the C function 
>>> and also return such a scalar.
>>>
>>> How do I do that?
>>>
>>> Thanks,
>>>
>>> Josef
>>>
>>>     
>>
>>
>> Did you looked at the eval_* functions in perlapi.pod?
>>
>> eval_pv
>>
>>      Tells Perl to eval the given string and return an SV* result.
>>      NOTE: the perl_ form of this function is deprecated.
>>              SV*     eval_pv(const char* p, I32 croak_on_error)
>>
>> eval_sv
>>
>>      Tells Perl to eval the string in the SV.
>>      NOTE: the perl_ form of this function is deprecated.
>>              I32     eval_sv(SV* sv, I32 flags)
> 
> No,
> 
> but some kind soul already pointed me at perlguts and there I found a 
> reference to SvPV() which does exactly what I want:
> 
> void
> scsi_cmd_in(fh, cmd, data_cnt)
>        PerlIO *fh
>        SV *cmd
>        int data_cnt
> PREINIT:
> ...
>        unsigned char *scsi_cmd;
>        STRLEN cmd_len;
> PPCODE:
> ...
>        scsi_cmd = SvPV(cmd, cmd_len);
> 
> Josef
> 

Hm, than I misunderstood you, I guess.
regards,
Reinhard