Re: [Chicken-users] anonymous enums

[Kon Lovett]

On Jul 12, 2007, at 1:29 PM, Martin DeMello wrote:

> Could someone give me an example of wrapping and using an anonymous c
> enum? The manual isn't too clear on that point.

'define-foreign-enum' needs a defined type identifier, so anonymous  
enums won't work. I use 'foreign-value' or 'define-foreign-variable',  
depending on the context.

Ex:

(define-macro (foreign-mask-set? ?bits ?c-nam)
  `(not (zero? (bitwise-and ,?bits (foreign-value ,?c-nam unsigned- 
integer32)))) )

(foreign-mask-set? sab "sessionIsRoot")

Here 'sab' is some integer and 'sessionIsRoot' is the ident of some  
elm of an anon enum. A bit(s) not zero test. In this case the value  
of 'sessionIsRoot' is only used once. (MacOS X frameworks use a lot  
of anonymous enums.)

Ex:

(define-foreign-variable c-sessionIsRoot unsigned-integer32  
"sessionIsRoot")

Here a compilation unit local Scheme variable 'c-sessionIsRoot' is  
created that "shadows" the C identifier 'sessionIsRoot'. (In this  
case do not "(set! c-sessionIsRoot ..)" since the C compiler will not  
like.) In this case I assume that the value of 'sessionIsRoot' is  
only used > once so repeating "(foreign-value sessionIsRoot unsigned- 
integer32)" is a pain .

NOTE: there is nothing special about the use of 'unsigned-integer32'  
as the type above. I am assuming all 32 bits are significant.

HTH,
Kon

> martin
>
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