Re: [9fans] Quick question on fossil

["Russ Cox" <rsc@swtch.com>]

On Mon, Jan 12, 2009 at 10:13 AM, Roman V. Shaposhnik <rvs@sun.com> wrote:
> I'm trying to read up on fossil implementation so
> that I can sustain an intelligent conversation with
> Andrey ;-)
>
> Now, the paper "Fossil, an Archival File Server" is
> pretty good, but here's one simple question that
> I can't find an answer to: there's a pointer to
> the root of the filesystem block from the Super.
> But what is the data structure that is expected
> to reside in that block? I thought it was VtRoot,
> but looking at a hexdump of the fossil file -- it
> doesn't look like one.

Super.active is the block number of a VtDirType block:
a block containing a few (I think 3) VtEntry structs.

VtRoot is the top of a vac archive.  it too contains
a pointer to a block containing a few VtEntry structs.
you could think of VtRoot as the vac equivalent of
fossil's Super.

if you

  cd /sys/src/cmd/fossil
  mk 8.view
  8.view /dev/sdC0/fossil

you should get a graphical file system data structure
browser, though since it is not part of the default
build it may not need some work to make
it build again.

russ