[openvrml-develop] Doc2 - adding big buffer

[Damian M. <da...@er...>]

I need to increase the speed of loading big, multi-megabyte VRML files.
They are of the order of 5MB. These then include another 30MB of related
VRML files, URLs related to textures, and the like.  To this end, I
proposed to change the size of the file buffers used by the classes Doc
and Doc2.

Correct me if whatever follows is garbage.

I think that a Doc is fairly easy.  I have added a extra entry to the
class which is an internal buffer and when a file is opened with

	::fopen

I simply allocate a lot of space and, like any STDIO file, use setvbuf.
I'll make it easy to change this size at a later stage.

Doc2 is a little more difficult.  It uses 'streambuf' and 'istream' but
then replaces their open functions and effectively.  In 'filebuf::open',
it simply calls the global gzopen out of 'ZLIB', i.e.

	gzFile gzopen(const char *path, const char *mode);

Then with the STDIO file,

	this->file

we new up some more buffer space, assign this space to the FILE with
another setvbuf and away we go.

This looks too simple. I might be getting in the road of other logic.

And have I missed something?  Does it go elsewhere in the code if the file
is not gzipped?

In the past, I have generally done my own big buffering and stayed away
from IOSTREAMs whenever performance was an issue so my experience in this
area is a little sparse.

Thanks - Damian (McGuckin)

Pacific Engineering Systems International, 22/8 Campbell St, Artarmon NSW 2064
Ph:+61-2-99063377 .. Fx:+61-2-99063468   | unsolicited email not wanted here !
Views and opinions here are mine and not those of any past or present employer