Re: udigits_to_I

[Sam S. <sd...@gn...>]

Hi Bruno,

> * Bruno Haible <oe...@py...t> [2005-01-25 11:53:38 +0100]:
>
> This function is unusable because underspecified:
>
>   /* bit sequence --> integer */
>   global maygc object udigits_to_I (void* digits, uintC len) {
>
> 1) The documentation should specify details about the input (is 'digits'
>    pointing to a single object of type void or to multiple ones?

digits points to a sequence of bytes, so it should probably be uint8*.

>   is len > 0 or can it be 0 ?

dunno.  it depends on the behavior of UDS_to_I() - which is not
specified in the comments either.
BTW, what does "there must be room for 1 digit below of MSDptr" mean?

> Is the input in big-endian or little-endian order?)

I don't know what "big-endian" and "little-endian" are.
In my kindergarten they taught only one way to record numbers with
digits: 123 = 1*100 + 2*10 + 3*1
So, byte sequence "123" represents the integer 1*256^2 + 2*256 + 3*1.

> 2) The doc should mention "can trigger GC"!

OK (although the "maygc" declaration should be enough, IMO)

> 3) In C, a 'void *' designates a pointer to memory of undefined contents.
>    It's not useful to access such memory. If there is data at *digits,
>    you need to specify the element size.

I guess, "digits" should be "uint8*".

> 4) Does the function write to *digits?

I don't think so - but UDS_to_I() does not declare its argument const...

> If not, then why is the 'digits' pointer not 'const'?

because I don't know what "const" means and I am sick of compiler
warnings and error triggered by such declarations.

> 5) The function is lacking a comment of its own in lispbibl.d. Imagine
> how unusable lispbibl.d would be if it contained only function
> declarations without comments!

right...

Maybe you could fix the comments of UDS_to_I() first?

-- 
Sam Steingold (http://www.podval.org/~sds) running w2k
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