On Sun, 8 May 2011, Sean P. DeNigris wrote:
> I want to call DCSGetTermRangeInString[1]:
>
> CFRange DCSGetTermRangeInString (
> DCSDictionaryRef dictionary,
> CFStringRef textString,
> CFIndex offset
> );
>
> The problem is I have no idea what to do about the return value and
> arguments. That is:
> <apicall: ??? 'DCSGetTermRangeInString' ???>
>
> How do I call this function using FFI? Where can I see an example?
You have to implement them (most of them). For example CFRange is a
struct, so you have to create a subclass of ExternalStructure for it. You
implement the class side #fields method which defines its fields, then
perform the class side #defineFields method to create the accessors for
them. For example CFRange is defined as[1]:
struct CFRange {
CFIndex location;
CFIndex length;
};
typedef struct CFRange CFRange;
So it has two fields, length and location, both have CFIndex as type.
CFIndex is signed long [2], so you'll implement #fields as:
CFRange class >> #fields
^#(
(length 'long')
(location 'long'))
Then evaluate [CFRange defineFields]. If this is done, then you can use
the class CFRange in the FFI call like:
<cdecl: CFRange 'DCSGetTermRangeInString' (... ... long) module: ...>
You don't have to implement C structs which you won't use in Squeak, just
pass around various C functions. In this case you can declare them as
void* and their class will be ExternalData. Don't forget that you have to
deallocate stuff allocated by C functions, to avoid memory leaks.
Levente
[1] <a href="http://developer.apple.com/library/mac/#documentation/CoreFoundation/Reference/CFBaseUtils/Reference/reference.html#//apple_ref/c/tdef/CFRange">http://developer.apple.com/library/mac/#documentation/CoreFoundation/Reference/CFBaseUtils/Reference/reference.html#//apple_ref/c/tdef/CFRange
[2] <a href="http://developer.apple.com/library/mac/#documentation/CoreFoundation/Reference/CFBaseUtils/Reference/reference.html#//apple_ref/c/tdef/CFIndex">http://developer.apple.com/library/mac/#documentation/CoreFoundation/Reference/CFBaseUtils/Reference/reference.html#//apple_ref/c/tdef/CFIndex
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