Richard,
Would you say that the life of a form, which serves as a "main menu" to get
to the rest of the program's functions, is a "short duration?" While the
program is being actively used, this form won't be up for very long at all.
But if the user starts the app, then doesn't start using it right away, the
form could be the active form for quite a long time. (Once again, "what is
the sound of one man answering his own question?"....)
Thanks for the examples.
Brian
> -----Original Message-----
> From: Richard Burmeister [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, June 07, 2001 10:39 AM
> To: Palm Developer Forum
> Subject: RE: Handles and pointers - basically interchangeable?
>
>
> > From: Brian Smith
> >
> > So, does this mean that it's *optional* to use MemPtrNew?
> If so, then I'm
> > really confused! If you don't *have* to use it, why would you?
> >
>
> As I understand it, you should use MemPtrNew or MemHandleNew
> to dynamically
> allocate memory when you want to avoid using up stack space,
> which is very
> limited, or when you won't know how much memory you need
> until the program
> is running. Whether to use MemPtrNew or MemHandleNew depends
> on how long
> you want the memory to be available. For short durations,
> such as during
> the lifetime of a single function, you can use either and so
> most people use
> MemPtrNew since it is simpler. For longer durations, you should use
> MemHandleNew, then lock it to get a pointer when you need to
> use the memory
> and unlock as soon as possible. That way, the OS can move
> the memory block
> if it needs to do so to allocate other memory.
>
> Here are some examples (not exhaustive) of memory allocation:
>
> 1. In a global at the start of your main.c (or whatever) -
> Char myString[20];
> This allocates 20 bytes for the string which will exist for
> the duration of
> your program.
>
> 2. In a global at the start of your main.c (or whatever) -
> Char * myString;
> This allocates 2 (or 4?) bytes for a pointer to some Chars
> which haven't
> been allocated yet. Then, to get memory for the string, you
> would call
> MemPtrNew or MemHandleNew. One advantage here is that you
> can allocate 20
> bytes or more or less as needed.
>
> 3. Inside a function -
> Char myString[20];
> This allocates 20 bytes for the string on the stack which
> will exist for the
> life of the function.
>
> 4, Inside a function -
> Char * myString;
> This allocates 2 (or 4?) bytes for the myString pointer on
> the stack. Then,
> to get memory for the string, you would call MemPtrNew or
> MemHandleNew,
> which allocate memory from the dynamic heap that will last
> until you free
> it. One advantage (or disadvantage, depending on how you
> look at it) with
> this is that you can allocate memory in one function that is
> used by another
> function (but then you have to be careful to clean up the memory!)
>
>
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