You are right that MemHandleResize will not change the handle.
In OS 2.0 and earlier, heap sizes were a max of 64K, and could have lots of stuff in
them. It was often that a MemHandleResize of a database handle would fail, requiring
it to be re-allocated in another heap. Doing what you are describing should work fine
in all current post-OS 2.0 implementations, but what about the future?
I am considering only supporting OS 3.5 and above with new software, and I want to
know if I can greatly simplify my memory management schemes in the future. One way
would be to do as you describe, only using MemHandeResize on memory handles.
But, I need a call from Palm to make sure they never go back to a multiple heap data
architecture. For example, would they consider doing multiple heaps in whatever they
intend to do with Nokia, or any other OS's they have planned? Is this a chip dependent
thing? It would be great if we could get a commitment to only have one data heap in
the OS.
In answer to your last question, DmResizeRecord simply calls MemHandleResize in post
2.0 implementations currently. But again, what about the future?
Shannon
>We use handles to create multiple of indices for a database. However we always use
>MemHandleResize. The declaration as par the API docs is
>
>Err MemHandleResize (VoidHandle h, ULong newSize)
>
>As you can see h is not a pointer to a handle, there is no way the function could
>change the value of h and return it. So, I assumed MemHandleResize never changes a
>handle. Where as DmResizeRecord returns a handle. Chances are there, that it will be
>different than the one I passed. Till now I have not faced any problems with this
>scheme.
>
>I understand this restricts us to one heap only. But, this is the best index
>referrence, we could think of. Record positions need to be updated constantly, and
>unique IDs involves a linear search.
>
>On a final note, the API docs say
>"On devices running version 2.0 or earlier of Palm OS � , the
>MemHandleResize function tries to resize the chunk only within
>the same heap, whereas DmResizeRecord will look for space in
>other data heaps if it cannot find enough space in the original heap."
>
>So, what happens in devices running version 3.0 or later of Palm OS?
>
>-Sugho-
>
>>From: Shannon <[EMAIL PROTECTED]>
>>Reply-To: "Palm Developer Forum" <[EMAIL PROTECTED]>
>>To: "Palm Developer Forum" <[EMAIL PROTECTED]>
>>Subject: Can Palm comment on the future of heaps?
>>Date: Wed, 15 Mar 2000 08:07:33 -0800
>>
>>Currently, the API specifies that whenever a storage handle gets resized, like
>through a DmResizeRecord, or a MemHandleResize, the handle might get relocated into a
>different data heap.
>>
>>However, since OS 3.0, there has only been one data heap, so that storage handles
>will not get moved when resized. The latest doc makes an offhand reference to this in
>the description of MemHandleResize.
>>
>>Can we count on this behavior in the future? In other words, will DmResizeRecord
>ALWAYS return the same handle in future OS's?
>>
>>It would be a huge advantage if we could count on non-moving data handles. One thing
>we could do with it is make multiple indexes into a database when an application
>starts up, and be able to count on the handles not changing while the application is
>running.
>>
>>Any comment from Palm?
>>
>>Shannon
>>
>>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>>Hands High Software
>>Award winning software for the Palm(tm) Computing platform
>>
>><http://www.handshigh.com/>
>>
>>[EMAIL PROTECTED]
>>
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>>
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Award winning software for the Palm(tm) Computing platform
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