| Reference counting [message #55818] |
Tue, 11 September 2007 23:32  |
Robbie
Messages: 165
Registered: February 2006
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Senior Member |
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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.pRef erence)
*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
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| Re: Reference counting [message #55837 is a reply to message #55818] |
Thu, 20 September 2007 13:13  |
JD Smith
Messages: 850
Registered: December 1999
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Senior Member |
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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
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| Re: Reference counting [message #55854 is a reply to message #55818] |
Tue, 18 September 2007 18:57 |
Robbie
Messages: 165
Registered: February 2006
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Senior Member |
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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
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