Re: Here's a post I would like forwarded... thanks! (fwd)
Justin Cormack <[email protected]> Wed, 9 Feb 2005 18:43:30 +0000 (GMT)
| Newsgroups | gmane.network.bit-torrent.general |
|---|---|
| Message-ID | <[email protected]> |
> >
> > Not to beat a dead horse, but...
> >
> > So I was re-reading the description of Merkle Hash Trees over at the
> > THEX specification (see
> > http://www.open-content.net/specs/draft-jchapweske-thex-02.html), and
> > I was thinking of implementing an efficient, array-based version in C.
>
> Hey, I got a post through!
>
> Well, getting back to sh4dowmatter's original post, I think it's a good
> idea. It sounds like it needs a bit more explaining, so here's some
> additional notes I've sent to Olaf on array based complete trees (the
> last level can be incomplete).
>
> Here's an example tree for a 9 piece torrent. The numbers are the node
> index for the nodes. The nodes with dashes around them are leaves, and
> represent pieces.
>
> 1
> |-----------------|
> 2 3
> |-------| |---------|
> 4 5 6 7
> |---| |---| |---| |---|
> 8 -9- -10- -11- -12- -13- -14- -15-
> |---|
> -16- -17-
Yes I would prefer a dense to a sparse tree.
This isnt the only way to achieve it of course, you can virtually pad
the content with zeros until it is a power of 2 in size, you know the hash
of all zeros so you dont compute it, then all rows are the same. This takes
up a little more space but is even more regular. There are probably other
solutions too.
j
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