embedlets-developer

Re: [ Christopher Smith ] [Embedlets-dev] RE: [muvium] Embedlet Container

[Gregg G. W. <gr...@sk...>]

>In designs where the wiring is fixed
>there is no issue since it is inexpensive to create a listener array of
>known size. Dynamic add/remove becomes more challenging.

An array of null references is empty.  Any loop through the array to deliver 
events can check for null listener references and skip those.  On insert, you 
just find a null spot, doubling the size of the array if there are none.
Delete just sets the entry to null.

The expansion of the array is a convienence that will happen seldom enough in 
production code that it is a great savings is weird behavior/crashes due to 
there not being any slots.  If you allocate a counter somewhere to count 
'listener list overflows', you can inspect when this happens.  You can also 
create a bit mask wide enough to hold an entry for each listener list to know 
which overflowed.

This gets a little tedious in administration, but the runtime overhead is 
minmized for most small size listener lists.

-----
gr...@cy...  (Cyte Technologies Inc)

RE: [ Christopher Smith ] [Embedlets-dev] RE: [muvium] Embedlet Container

[James C. <ca...@vi...>]

>An array of null references is empty.  Any loop through the array to
deliver 
>events can check for null listener references and skip those.  On
insert, you 
>just find a null spot,

This is exactly how it is implemented in the muvium APT listeners..
(except its' done in assembler) except I am not doubling the size at the
moment rather depending on the fixed sizing ( user defineable ). Down
the trek it will be easy enough to do the slot size doubling.

The thing about the listener model is that it is well understood and
efficient which is why I prefer it for the container. What needs to be
considered is how to publish events that interact with each other. It
might be as simple a declaring Listener Interfaces..


James Caska
www.muvium.com
uVM - 'Java Bred for Embedded'



-----Original Message-----
From: Gregg G. Wonderly [mailto:gre...@po...] 
Sent: Tuesday, 24 June 2003 5:20 AM
To: emb...@li...
Cc: mu...@ya...
Subject: Re: [ Christopher Smith ] [Embedlets-dev] RE: [muvium] Embedlet
Container



>In designs where the wiring is fixed
>there is no issue since it is inexpensive to create a listener array of

>known size. Dynamic add/remove becomes more challenging.

An array of null references is empty.  Any loop through the array to
deliver 
events can check for null listener references and skip those.  On
insert, you 
just find a null spot, doubling the size of the array if there are none.
Delete just sets the entry to null.

The expansion of the array is a convienence that will happen seldom
enough in 
production code that it is a great savings is weird behavior/crashes due
to 
there not being any slots.  If you allocate a counter somewhere to count

'listener list overflows', you can inspect when this happens.  You can
also 
create a bit mask wide enough to hold an entry for each listener list to
know 
which overflowed.

This gets a little tedious in administration, but the runtime overhead
is 
minmized for most small size listener lists.

-----
gr...@cy...  (Cyte Technologies Inc)



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