Re: [opendemo-devel] zlib problems

[Conor D. <co...@ma...>]

Hello,

> Hello!
>
> On Tue, Jan 22, 2002 at 12:27:46AM -0600, Conor Davis wrote:
> > I've pretty much given up on getting zlib to work with qvm files,
especially
> > with the garbage return value bug. I started to do a bunch of hacks the
> > stored return values in global variables, but that addresses the
symptoms
> > and not the problem. Anyway, in my testing I've found that the qvm
maximum
> > stack size seems to be 512K (after that quake3 crashes). I suspected
that
> > zlib was exceeding the maximum stack size, but with 512K it looks
doubtful.
> Enough is enough. Now I look in the created asm files  and learn this asm
> language. It can't be more difficult than any other assembler language.
After
> that I'll write a tool calculate the maximum used stack frame.

Unless qvm asm is very different from native code, the stack size should be
about the same between qvm and native code. It seems like there should be a
tool that does this for 'real' programs, but I didn't find one. What would
be more interesting is where return pointers and return values are stored,
as they apparently aren't stored in the same place as local variables and
function parameters. It boggles my mind as to how they could get corrupted.

> > Instead of zlib, maybe we should use a binary XML format similar to
wbxml?
> Why not the unchanged wbxml? As far as I can remember, the Java code in
> opendemo/tools/com/machinima/opendemo
> contains a fully working xml text <-> wbxml converter. It was one of the
first
> things I did for OpenDemo. The only thing to correct it the tag string <->
code
> table.

From what I remember, wbxml only stores XML structure data binary, so for
example:
<origin index="123">456</origin>
the numbers would still be encoded as text. I was thinking of something
where you feed the parser a schema (that specifies datatypes), and it could
store numbers as binary. However, this whole binary XML thing should be a
last resort if we can't get zlib to work, or if it is not fast enough. Then
we would have to decide which is more desirable: an arcane compression
format or an arcane binary XML format.

-Conor