Re: Passing scalars to C functions

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

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Josef Möllers (Pinguinpfleger bei FTS)
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