Reference counting

I am using reference counting to automatically free pointers which are
no longer in use. I've come across a problem when I use save and
restore. I find that I really need to recalculate the number of
references after I restore an object. Is there any way to
programatically determine the number of references to a pointer?

Thanks

Robbie

Example code attached:

pro refcount::GetProperty, VALUE=value

if (arg_present(value) and (n_elements(*self.value) gt 0)) then value
= *self.value

end

pro refcount::SetProperty, VALUE=value

if (n_elements(value) gt 0) then *self.value = value

end

function refcount::Copy

obj =
obj_new('refcount',P_VALUE=self.pValue,P_REFERENCE=self.pReference)

*self.pReference++

return, obj

end

pro refcount::Cleanup

*self.pReference--

if (*self.pReference le 0) then begin

ptr_free, self.pReference

ptr_free, self.pValue

endif

end

function refcount::init, P_VALUE=pValue, P_REFERENCE=pReference,
VALUE=value

if (n_elements(pValue) gt 0) then self.pValue = pValue $

else self.pValue = ptr_new(/ALLOCATE_HEAP)

if (n_elements(pReference) gt 0) then self.pReference = pReference $

else self.pReference = ptr_new(1)

if (n_elements(value) gt 0) then *self.pValue = value

return, 1b

end

pro refcount__define, struct

struct = {refcount, $

pValue: ptr_new(), $

pReference: ptr_new() $

}

end

pro refcount_example1

a = obj_new('refcount',VALUE=indgen(100))

b = a -> copy()

obj_destroy, [a,b]

help, /heap

end

pro refcount_example2_restore

restore

obj_destroy, [a]

help, a

end

pro refcount_example2

a = obj_new('refcount',VALUE=indgen(100))

b = a -> copy()

save, a

obj_destroy, [a,b]

help, a, b

refcount_example2_restore

help, /heap

end

For future reference, there is an undocumented routine called
HEAP_NOSAVE.

HEAP_NOSAVE allows me to specify that the reference counting pointer
should not be saved.
I can then recount the number of references with a single pass of
the ::RESTORE method.

I hope this is perfectly clear to all those concerned :-P

Robbie

http://barnett.id.au/idl

On Tue, 18 Sep 2007 18:57:12 -0700, Robbie wrote:

>
> For future reference, there is an undocumented routine called
> HEAP_NOSAVE.
>
> HEAP_NOSAVE allows me to specify that the reference counting pointer
> should not be saved.
> I can then recount the number of references with a single pass of
> the ::RESTORE method.
>
> I hope this is perfectly clear to all those concerned :-P

That's a useful function, and documented for me in v6.3. I have long
saved objects to disk for project storage, but "strip" by hand the
pointers I don't wish to save (e.g. ones containing widget trees, etc.).
This is a much cleaner method: simply call HEAP_NOSAVE, ptr, and even if
the save crashes (e.g. out of disk space), your object will be intact.

Thanks,

JD

Reference counting - Idl-pvwave