On a Windows Mobile device, does it make sense to cache data "in memory"?

Question

I'm writing a Windows CE application, and I want to play a sound (a short wav file) when something happens. Since this sound will be played often, my first instinct was to load the wav file into a memory stream and reuse that stream instead of reading the file every time.

But then it occured to me that these Windows Mobile devices only have one kind of memory, which is used both for data storage (= the file system) as well as for program memory; there's even a nice slider in the control panel which you can use to delegate memory to either storage or program execution. So, theoretically, reading a file from the file system (or some value from a SQL Server CE database) should take (almost) the same amount of time as reading this value from some in-memory object, right?

Is this assumption correct (i.e., in-memory caching on application level doesn't make sense here) or did I miss something? For simplicity, let's assume that only the internal memory of the device is used (no memory card).

Answer 1

The assumption may or may not be valid. Where in storage does it reside? If it's persistent storage (like a storage card folder or anything else that remains when you hard reset) then it's backed by Flash, which is way, way slower than RAM and there will be a difference in load perf, though how much it might impact your app I can't say - only testing will tell you that.

Answer 2

When I want to play a short WAV file on Windows Mobile (e.g. notification sound). I usually add it as a resource to my executable. AFAIK resources are loaded into RAM since they are part of the executable image. You can then conveniently call PlaySound() with the SND_RESOURCE (and probably OR that with SND_ASYNC too so the call isn't going to block while the file is being played) flag.