Re: [steem] The come back of the Snapshot
- From: "Steem Authors" <russ@xxxxxxxxxxxxxxxxxxxxxxx>
- To: "Steem Discussion" <steem@xxxxxxxxxxxxx>
- Date: Tue, 31 Dec 2002 20:59:18 -0000
Hi,
> Hello everbody, and merry Xmas !
Thanks, hope you had a great Christmas and have a happy new year.
> The snapshot is divided into 2 parts:
> -The Header
> -Datas (the st memory), writted from the end of the st
> memory to the beginning (so in reverse order, but the
> high bit on left and low bit on right, cool)
>
> Here come my questions, (if you prefere make a
> summary, i'll be happy to and all who want use the
> snapshot too ^^ ):
> - can u correct me if something is wrong in the
> explanation above ?
It looks correct, but all this big endian/little endian stuff confuses the
hell out of me. If I give an example it should make things simpler. Say the
snapshot you want to decode was saved with the ST set to 1Mb and the first
word of RLE encoded data is 2000. You would read in the next 4000 bytes
(2000 words) from the file. Now the first of these bytes you read in would
be the byte that was at address $0FFFFF on the ST, the next byte would be
$0FFFFE and so on all the way down to $0FF05F.
> - Is the Header RLE compressed too (so all the
> snapshot) or just the Datas ? If i look at the file,
> it seems only Datas.
Yes that is correct, the header isn't compressed.
> - where's the variable file length ? is it an offset
> to the beginning of the datas (st memory) ?
There are variable length blocks in the header (mainly strings) that
make the length strange. To read the memory you first have to skip through
the header to an offset, that was added in v1.4, I wish I had put it at the
start in v1.0! I suppose I wasn't really thinking of forwards and backwards
compatibility then, v1.0 was so bad we didn't expect anyone to use it. :)
> - can u give your class, information or the structure
> of the Header ?
I'll send you what you need to skip to the offset (in a private mail, too
boring for this list).
> - can u think you are going to change a lot of things
> for the snapshot in the next release ? (if so we can
> wait for it)
I will always try and maintain forward and backwards compatibility, I don't
see any reason why I won't be able to do that. The header up to the offset
will be the same on all snapshots saved from Steem v1.4 onwards.
> - perhaps can u raise the size of the dump in the
> debug to a variable size ? (so no rle compression and
> no header... cool ^^ )
Yes I've done that in the next version, you will be able to dump the whole
ST memory now.
> I hope my questions are well formed and not too lazy.
They're no problem at all, I hope my answers aren't too cryptic. :D
Good luck,
Russell Hayward
--
Steem - http://www.blimey.strayduck.com/
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