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VENTI-CLIENT(2)               System Calls Manual              VENTI-CLIENT(2)



NAME
       vtconnect,   vthello,  vtread,  vtwrite,  vtreadpacket,  vtwritepacket,
       vtsync, vtping, vtrpc, ventidoublechecksha1 - Venti client

SYNOPSIS
       #include <u.h>
       #include <libc.h>
       #include <venti.h>

       Packet* vtrpc(VtConn *z, Packet *p)

       int     vthello(VtConn *z)

       int     vtconnect(VtConn *z)

       int     vtread(VtConn *z, uchar score[VtScoreSize],
                       uint type, uchar *buf, int n)

       int     vtwrite(VtConn *z, uchar score[VtScoreSize],
                       uint type, uchar *buf, int n)

       Packet* vtreadpacket(VtConn *z, uchar score[VtScoreSize],
                       uint type, int n)

       int     vtwritepacket(VtConn *z, uchar score[VtScoreSize],
                       uint type, Packet *p)

       int     vtsync(VtConn *z)

       int     vtping(VtConn *z)

       extern int ventidoublechecksha1;  /* default 1 */

DESCRIPTION
       These routines execute the client side of the venti(6) protocol.

       Vtrpc executes a single Venti  RPC  transaction,  sending  the  request
       packet p and then waiting for and returning the response packet.  Vtrpc
       will set the tag in the packet.  Vtrpc frees p, even on  error.   Vtrpc
       is typically called only indirectly, via the functions below.

       Vthello  executes  a hello transaction, setting z->sid to the name used
       by the server.  Vthello is typically called only indirectly, via vtcon‐
       nect.

       Vtconnect  calls  vtversion  (see  venti-conn(2))  and vthello, in that
       order, returning success only if both succeed.  This sequence  (calling
       vtversion and then vthello) must be done before the functions below can
       be called.

       Vtread reads the block with the given score and type from  the  server,
       stores  the  returned  data in memory at buf, and returns the number of
       bytes read.  If the server's block has size larger than n, vtread  does
       not modify buf and returns an error.

       Vtwrite writes the n bytes in buf as a block of the given type, setting
       score.

       Vtreadpacket and vtwritepacket are like vtread and vtwrite  but  return
       or  accept the block contents in the form of a Packet.  They avoid mak‐
       ing a copy of the data.

       Vtsync causes the server to flush all pending write  requests  to  disk
       before returning.

       Vtping executes a ping transaction with the server.

       By  default,  vtread  and  vtreadpacket check that the SHA1 hash of the
       returned  data  matches  the   requested   score,   and   vtwrite   and
       vtwritepacket  check  that  the returned score matches the SHA1 hash of
       the written data.  Setting ventidoublechecksha1 to zero disables  these
       extra checks, mainly for benchmarking purposes.  Doing so in production
       code is not recommended.

       These functions can be called from multiple threads or procs simultane‐
       ously to issue requests in parallel.  Programs that issue requests from
       multiple threads in the same proc should start separate  procs  running
       vtsendproc and vtrecvproc as described in venti-conn(2).

SOURCE
       /sys/src/libventi

SEE ALSO
       venti(2), venti-conn(2), venti-packet(2), venti(6)

DIAGNOSTICS
       Vtrpc  and  vtpacket return nil on error.  The other routines return -1
       on error.

       Vtwrite returns 0 on success: there are no partial writes.



                                                               VENTI-CLIENT(2)