VENTI-CLIENT(2)                                   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) pro-
          tocol.

          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 vtconnect.

          Vtconnect calls vtversion (see venti-conn(2)) and vthello,
          in that order, returning success only if both succeed.  This

     VENTI-CLIENT(2)                                   VENTI-CLIENT(2)

          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 making 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
          simultaneously 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.