Re: [Chicken-users] How to deal with bit sets in chicken?

[Kon Lovett]

On May 30, 2009, at 10:36 AM, Anthony Carrico wrote:

> For example, according epoll_ctl(2) on the Linux AMD64 platform, the
> following are __uint32_t.
>
> (foreign-declare "#include <sys/epoll.h>\n")
> (define-foreign-variable _EPOLLET unsigned-integer32 "EPOLLET")
> (define EPOLLET _EPOLLET)
> (define-foreign-variable _EPOLLONESHOT unsigned-integer32  
> "EPOLLONESHOT")
> (define EPOLLONESHOT _EPOLLONESHOT)
>
> #;2> EPOLLET
> 1.84467440715621e+19
> #;3> EPOLLONESHOT
> 1073741824
> #;4>
>
>
> Here I declare them as int:
>
> (define-foreign-variable _EPOLLET int "EPOLLET")
> (define EPOLLET _EPOLLET)
> (define-foreign-variable _EPOLLONESHOT int "EPOLLONESHOT")
> (define EPOLLONESHOT _EPOLLONESHOT)
>
> #;8> EPOLLET
> -2147483648
> #;9> EPOLLONESHOT
> 1073741824
> #;10>
>
> It seems like I can only get fixnums or flonums, is there a way to  
> deal
> with genuine 32-bit integers? What is the best way to declare

-2147483648 is the 2's complement of 2147483648 is  
18446744071562100000 (1.84467440715621e+19) & 18446744071562100000 is  
0xFFFFFFFF80007D20.

So your bits are persevered ... at least on 64-bit hardware. I suggest  
using 'unsigned-integer32' as the argument & return type when you know  
for sure that ALL 32 bits are significant so that the interface is  
compliant w/ 32-bit hardware. The flonum representation will be  
properly converted.

With Chicken (& other "high level" programming notations) "type" is  
not always synonymous w/ "representation".

Chicken will always treat a flonum w/o a fraction as an integer.
Ex: (integer? 1.84467440715621e+19) ;=> #t

>  and
> manipulate these in Chicken?

Depends on what you mean by "manipulate". If you plan on using the  
'library' unit "bitwise-" operations on 32-bit hardware then there is  
a problem with the above magnitude. If all you need is I/O conversion  
w/ C library routines then the above advise is good. Otherwise we need  
to talk.

(See the unreleased Chicken 4 "err5rs-arithmetic-bitwise" module for a  
more generic set of operations that can deal with "real" machine words  
on 32 & 64 bit machines.)

> Thank you.
>
> --
> Anthony Carrico
>
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Best Wishes,
Kon