DmWrite is atomic (it uses a system semaphore). You could just structure
your code so that your record is constructed on the heap, then written to
data memory with a single DmWrite. If you need to do in-place editing,
initialize your header to an invalid value first, record your data, then
write your valid data using a single DmWrite call last. Then check for a
valid header before using the record.
Good Luck,
-jjf
-----Original Message-----
From: Shannon [mailto:[EMAIL PROTECTED]]
Sent: Friday, May 19, 2000 9:57 AM
To: Palm Developer Forum
Subject: Semaphores
How do we handle data integrity issues with semaphores?
For example, lets say you are writing data to a database, and you also want
to write a size to the database as well.
I currently allocate the memory, write the data, then write the size.
However, since the OS is multi-threaded, the pager card, for example, could
interrupt into the middle of this operation, add data to the storage memory,
potentially fill up storage memory or crash, and then I am left with only
the first write operation and not the second, and therefore corrupt data.
Are there any OS calls to prevent an interrupt at this level?
Shannon
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Hands High Software, Inc.
Award winning software for the Palm OS platform
<http://www.handshigh.com/>
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