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Venti - access to Venti content-addressed filestore.


include "venti.m";
venti := load Venti Venti->PATH;
Session: import venti;

init:			fn();
unpackentry:	fn(d: array of byte): ref Entry;
unpackroot:	fn(d: array of byte): ref Root;

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;


Venti is a block storage server intended for archival applications. The 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 dial(2)). On a Venti server, a block is addressed by the SHA1 hash of the contents of that block, known as a score, and represented as a Score adt. Blocks are additionally tagged with a type, facilitating recovery in the event of corruption. A Session represents an session with a Venti server.

New performs the initial handshake with the Venti server, returning established Session.
Read tries to retrieve the block corresponding to score, and of type etype. The block must be no longer than maxn bytes. Etype is conventionally one of the constants Roottype, Dirtype, Datatype or Pointertype[0-9], where the different Pointertypes represent different depth levels within a Venti tree.
Write writes the data in buf to the Venti server. The block will be tagged with type etype. It returns a tuple, say (okscore); on error, ok is -1, otherwise ok is 0 and score contains the Venti score for the block that has been written.
Sync tells the Venti server to make sure that all data is committed to active storage.




to do: Score adt entry packing/unpacking other Vmsgs, Session.rpc()?

VENTI(2 ) Rev:  Thu Feb 15 14:43:26 GMT 2007