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Re: [Gnash-dev] Re: Bitwise stream reading performance

From: strk
Subject: Re: [Gnash-dev] Re: Bitwise stream reading performance
Date: Mon, 27 Aug 2007 14:54:42 +0200

On Mon, Aug 27, 2007 at 02:44:48PM +0200, Udo Giacomozzi wrote:
> Hello strk,
> Monday, August 27, 2007, 2:15:42 PM, you wrote:
> s> gnash::stream exposes a get_underlying_stream, which is currently used
> s> by some tag readers (embedded bitmaps usually). If we can remove any
> s> use of the underlying file, cache can be enabled at the gnash::stream 
> level,
> s> otherwise we're stuck in doing it in the tu_file directly.
> Why do they need access to the underlying stream? Odd.

Probably a left-over. Should be easy to fix.

> I could implement such a cache if someone can point me to
> documentation explaining the byte structure of SWF files (first of
> all, is it MSB or LSB first?).

I added a testcase (StreamTest). As long as that one work you should
be fine.

> s> Finally, we might want to implement bitcache as a separate class,
> s> which could be used by an higher level (say, shape reading).
> How would shape reading benefit from that? I think it's enough if we
> implement it in the stream class.

Benefit would be locality of references. The final user would initialize
the "BitsCache" and use that (assuming it knows in advance how many bytes
will be needed).
Anyway, go with the stream implementation, I'll work on removing access to
the underlying tu_file.


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