ref: 54bac038f411c10a596adf84c06df32f8c7c4c53
dir: /man/2/venti/
.TH VENTI 2
.SH NAME
Venti \- access to Venti content-addressed filestore.
.SH SYNOPSIS
.EX
include "venti.m";
venti := load Venti Venti->PATH;
Session: import venti;
init: fn();
Session: adt {
new: fn(fd: ref Sys->FD): ref Session;
read: fn(s: self ref Session, score: Venti->Score, etype: int, maxn: int): array of byte;
write: fn(s: self ref Session, etype: int, buf: array of byte): (int, Venti->Score);
sync: fn(s: self ref Session): int;
};
Score: adt {
a: array of byte;
eq: fn(a: self Score, b: Score): int;
text: fn(a: self Score): string;
parse: fn(s: string): (int, Score);
zero: fn(): Score;
};
.EE
.SH DESCRIPTION
.I Venti
is a block storage server intended for archival applications.
The
.I Venti
module provides low-level access to a Venti server.
The module assumes that the physical connection
to the server has already been established
(for example, by
.IR dial (2)).
On a Venti server, a block is addressed by the SHA1 hash of
the contents of that block, known as a
.IR score ,
and represented as a
.B Score
adt.
Blocks are additionally tagged with a
.IR type ,
facilitating recovery in the event of corruption.
A
.B Session
represents a session with a Venti server.
.TP
.IB s .new(\fIfd\fP)
.B New
performs the initial handshake with the Venti server,
returning established
.BR Session .
.TP
.IB s .read(\fIscore\fP,\ \fIetype\fP,\ \fImaxn\fP)
.B Read
tries to retrieve the block
corresponding to
.IR score ,
and of type
.IR etype .
The block must be no longer than
.I maxn
bytes.
.I Etype
is conventionally one of the constants
.BR Roottype ,
.BR Dirtype ,
.BR Datatype
or
.BR Pointertype [0-9],
where the different
.BR Pointertype s
represent different depth levels within a Venti tree.
.TP
.IB s .write(\fIetype\fP,\ \fIbuf\fP)
.B Write
writes the data in
.I buf
to the Venti server.
The block will be tagged with type
.IR etype .
It returns a tuple, say
.RI ( ok ,\ score );
on error,
.I ok
is -1, otherwise
.I ok
is 0 and
.I score
contains the Venti score for the block that has been written.
.TP
.IB s .sync()
.B Sync
tells the Venti server to make sure that all data is committed to
active storage.
.SH SOURCE
.B /module/venti.m
.br
.B /appl/lib/venti.b
.SH BUGS