Trying to write a plugin - how to store a pointer

[Todd Blanchard]

My plan is to add the class containing the pointer to the startup/ 
shutdown lists and make them zombies (I can't reasonably re-animate  
them with full state I don't think).

So I've got this:

primNewRuntime: bytesToAllocate

	| rtid size |

	self export: true.
	self var: #rtid type: 'void *'.
	self var: #size type: 'unsigned int'.
	size := interpreterProxy positive32BitValueOf:  bytesToAllocate.
	rtid := self cCode: 'LIB_NewRuntime(size)'.
	^interpreterProxy positive32BitIntegerFor:  rtid.

Look OK?
Is there a good way to make it future proof for 64 bit addresses?   
Off the top of my head I can think of:

primNewRuntime: bytesToAllocate

	| rtid size |

	self export: true.
	self var: #rtid type: 'void *'.
	self var: #size type: 'unsigned int'.
	(self cCode: 'sizeof(void*)') = 4 ifTrue:
	[
		size := interpreterProxy positive32BitValueOf:  bytesToAllocate.
		rtid := self cCode: 'LIB_NewRuntime(size)'.
		^interpreterProxy positive32BitIntegerFor:  rtid.
	]
	ifFalse:
	[
		size := interpreterProxy positive64BitValueOf:  bytesToAllocate.
		rtid := self cCode: 'LIB_NewRuntime(size)'.
		^interpreterProxy positive64BitIntegerFor:  rtid.
	]

Maybe you know a better way?

On Jan 23, 2006, at 3:29 PM, John M McIntosh wrote:

> Although this seems correct at first, you run into trouble because  
> SmallInteger has a finite range smaller than a 32bit integer.
> Ignoring the 64bit needs  you would pass the value in as a Oops  
> then do this
>
> 	pv := interpreterProxy positive32BitValueOf:  anAddressOops.
> or perhaps
> use positive64BitIntegerFor:  ?
>
> on return you do this to pass the bits back.
> 	^ interpreterProxy positive32BitIntegerFor:  address
>
> It's likely you need to look at finalization and registering an  
> external object (Smalltalk registerExternalObject: )
> to ensure you free things when the smalltalk object is GCed, and to  
> check to see if the object is still valid save after an image  
> restart to
> prevent passing in a bogus address which your C plugin would  
> cheerfully attempt to use.  MPEGFile has some example code in it.
>
>
> On 23-Jan-06, at 3:01 PM, Todd Blanchard wrote:
>
>> For various reasons, I'm wanting to build a plugin to a library  
>> that requires me to hold onto pointers to things.  This means I  
>> need to store the pointer in an ivar in a squeak object and use it  
>> on subsequent calls.
>>
>> Can I get away with using a SmallInteger for this?  Basically  
>> doing something like:
>>
>> primNewContext
>> 	| ctx |
>>
>> 	self export: true.
>> 	self primitive: 'primCreateContext' parameters: #().	
>> 	self var: #ctx type: 'int'.
>> 	ctx := self cCode: 'LIB_NewContext()'.
>> 	^ctx.
>>
>> primDestroyContext: ctx
>> 	self export: true.
>> 	self primitive: 'primDestroyContext' parameters: #(SmallInteger).	
>> 	self cCode: 'LIB_DestroyContext((void*)ctx)'.
>>
>> Or is this evil and I should consider a different technique?
>> If this is evil, what is the good way to store external addresses  
>> in ivars?
>>
>> Thanks
>
> --
> ====================================================================== 
> =====
> John M. McIntosh <johnmci at smalltalkconsulting.com> 1-800-477-2659
> Corporate Smalltalk Consulting Ltd.  http:// 
> www.smalltalkconsulting.com
> ====================================================================== 
> =====
>