[jawsscripts] Re: Resizing arrays
- From: Soronel Haetir <soronel.haetir@xxxxxxxxx>
- To: jawsscripts@xxxxxxxxxxxxx
- Date: Thu, 5 Jan 2012 11:35:05 -0900
Yes, jaws script objects are referenced counted, it's the same process
that occurs if the variable were to simply go out of scope. I don't
know that I've ever seen a language of this sort that requires manual
memory cleanup. I suppose such might exist, but it would be very much
the exception.
On 1/5/12, Travis Roth <travis@xxxxxxxxxxxxxx> wrote:
> Yes I thought the array copy was by reference as well.
>
> I have the same problem of not knowing array size in advance.
> But it does look useful that you can just make a new array on the existing
> variable, I hadn't realized that was possible. Does the old array just stop
> existing when new is called again? We've lost access to it but I am just
> wondering if JAWS does any garbage collection. I am thinking in the case of
> the default scripts, where those global variables are in existence until
> JAWS is unloaded, if garbage collection does not automatically occur using
> new repeatedly would start to be a memory leak.
>
> Like the ideas... Thanks everyone.
>
> -----Original Message-----
> From: jawsscripts-bounce@xxxxxxxxxxxxx
> [mailto:jawsscripts-bounce@xxxxxxxxxxxxx] On Behalf Of Doug Lee
> Sent: Thursday, January 05, 2012 1:55 PM
> To: jawsscripts@xxxxxxxxxxxxx
> Subject: [jawsscripts] Re: Resizing arrays
>
> A couple clarifications:
>
> First, to me at least, a "deep copy" is a full duplication of something with
> all subparts. My understanding of "s2 = s1" where they are arrays is that,
> in JAWS, only the pointer is copied. It still works for your usage though,
> so this is mostly just behind-the-scenes stuff for this case.
>
> Second though, your code assumes array sizes, and most of my cases don't
> have a clue in advance what size to use. As an example, consider code that
> creates a structure of information for each entry in a chat window. If the
> process of counting entries is as expensive as that for actually retrieving
> them, there's no reasonable way to know in advance how big to make the
> array. A collection becomes more efficient in this case, because it is
> dynamic while still being amenable to random access.
>
> On Thu, Jan 05, 2012 at 03:59:00PM -0300, Andrew Hart wrote:
> I don't understand your need for collections in order to use arrays
> globally. You just create the array at the size you need. If you need to
> add to it, you just fob it off to a local variable, assign a new larger
> array to the global var and then copy the array elements in the local var to
> the global one. Then, to finish, you erase the copy of the array by
> assigning it an unassigned array var of the same type, much as you would do
> with Object vars.
>
> For example:
>
> Var
> StringArray s1,
> StringArray S2,
> StringArray NULLStringArray
> s1 = New StringArray[5]
> ; fill the array with stuff
> ...
> ;Copy the array (this is a deep copy, not a shallow copy that only ;passes a
> reference pointer)
> s2 = s1
> s1 = New StringArray[10] ; make the array bigger ; Now copy the contents of
> s2 to s1 For i = 1 To 5
> s1[i] = s2[i]
> EndFor
> ; erase the array.
> ; Since JAWS performs deep array copies, it should reduce s2 to its ;minimal
> memory footprint, allowing the space to be reclaimed by the ;heap when
> appropriate conditions prevail
> s2 = NULLStringArray
>
>
> If you're serious about regularly resizing arrays, I'd recommend making a
> few functions using the relevant bits of the above example for resizing
> arrays of different types. You'd pass the array being resized by reference
> (using ByRef in the function declaration). Also, as this is a linear time
> operation, doing it a lot could slow things down if you are dealing with big
> arrays. Tricks for dealing with that are to always make the array bigger
> than what you need. For example, you could always double the size of the
> array whenever you run out of space and then resize it to conserve memory by
> removing unused portions later if it is not likely to be added to for a
> while.
>
> Hth,
> Andrew.
>
> On 5/01/2012 2:32 PM, Travis Roth wrote:
>> Perhaps a combination of a collection and an array would work then?
>> The documentation states that a collection can hold arrays. So when a
>> new array is wanted, delete the old one in the collection and make a new
> one.
>>
>> I am not sure what type of performance that'd give, but might be
>> another workaround.
>>
>> The reason for not just creating new arrays is I need them to be
>> global, and there'd be no way to keep track of the names, or at least
>> not a practical way.
>> Bbut a collection may solve that.
>>
>> -----Original Message-----
>> From: jawsscripts-bounce@xxxxxxxxxxxxx
>> [mailto:jawsscripts-bounce@xxxxxxxxxxxxx] On Behalf Of Doug Lee
>> Sent: Thursday, January 05, 2012 11:26 AM
>> To: jawsscripts@xxxxxxxxxxxxx
>> Subject: [jawsscripts] Re: Resizing arrays
>>
>> JAWS 12 introduced a CollectionRemoveItem function for that.
>>
>> On Thu, Jan 05, 2012 at 11:23:32AM -0600, Travis Roth wrote:
>> Kind of messy but I see your reasoning.
>> How do you remove an item from a collection?
>>
>>
>> -----Original Message-----
>> From: jawsscripts-bounce@xxxxxxxxxxxxx
>> [mailto:jawsscripts-bounce@xxxxxxxxxxxxx] On Behalf Of Doug Lee
>> Sent: Thursday, January 05, 2012 10:21 AM
>> To: jawsscripts@xxxxxxxxxxxxx
>> Subject: [jawsscripts] Re: Resizing arrays
>>
>> In the absence of knowledge of a way to do that, I've been using
>> collections as dynamic arrays, where the keys are things like
>> intToString(i). You do need to stringify the keys though. When I do
>> that, I also sometimes include a count key that I keep updated when
>> adding or removing elements. This also allows for efficient sparse
>> arrays but does complicate their management a bit and precludes things
>> like inserts/deletes where elements slide in to fill the hole or make
> room.
>>
>> On Thu, Jan 05, 2012 at 10:17:13AM -0600, Travis Roth wrote:
>> Is it possible to resize arrays in JAWS script?
>> It appears that the arrays are dynamically sized at runtime because
>> the new keyword is used.
>> But the documentation on the website does not seem to discuss
>> destroying or resizing arrays?
>> This may not be an issue for local variables, but I am thinking for a
>> global array where at some point it may be desireable to store
>> something larger than was originally set for.
>>
>>
>>
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> Accessibility-on-Demand mailto:doug.lee@xxxxxxxxxxxxxxxx
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