RE: [Gamedevlists-brew] porting a database file from BREW to J2ME

[Tom H. <to...@am...>]

> -----Original Message-----
> 1) Has anyone noticed a phone that completely decompresses the JAR,
> including non-class files, into memory when the app is first loaded?  That
> is, do all known J2ME phones keep the resources compressed until
> requested?

Yes. A file is only loaded into memory when you open it. To be even more
specific, if you're loading a 100k file and using the stream mechanism to
get to a record 50k in, then 50k of the file will be loaded into memory.

So far I haven't found a phone that would let you seek to the 50k mark
without having the preceding 50k in your heap. As I figure it, this is due
to the file you're loading being zipped inside the jar, so you need to
decompress from the start to the point where you want ... you can't just
jump to it. In case it isn't obvious, this also means you have significant
performance issues if you're going to be seeking all over the place in a
file.

It might be interesting to just store the file in the jar, and not deflate
it. Maybe it would allow you do seek with good performance and without
hitting the heap if the file isn't compressed. You would need to create the
it with a tool other than jar, or modify the jar with WinZip after or
something.

> 2) Do any phones degrade in performance when large numbers of small files
> are stored in the jar file?

I haven't run into any performance issues, but there's a pretty large
overhead per file (~150 bytes) so if download size is a concern having lots
of files is a very bad thing.

Tom