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	tventi-client.3 (3343B)
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	1 .TH VENTI-CLIENT 3
	2 .SH NAME
	3 vtconnect, vthello, vtread, vtwrite, vtreadpacket, vtwritepacket, vtsync…
	4 .SH SYNOPSIS
	5 .ft L
	6 #include <u.h>
	7 .br
	8 #include <libc.h>
	9 .br
	10 #include <venti.h>
	11 .ta +\w'\fLPacket* 'u +\w'\fLxxxxxxxx'u
	12 .PP
	13 .B
	14 Packet* vtrpc(VtConn z, Packet p)
	15 .PP
	16 .B
	17 int vthello(VtConn *z)
	18 .PP
	19 .B
	20 int vtconnect(VtConn *z)
	21 .PP
	22 .B
	23 int vtread(VtConn *z, uchar score[VtScoreSize],
	24 .br
	25 .B
	26 uint type, uchar *buf, int n)
	27 .PP
	28 .B
	29 int vtwrite(VtConn *z, uchar score[VtScoreSize],
	30 .br
	31 .B
	32 uint type, uchar *buf, int n)
	33 .PP
	34 .B
	35 Packet* vtreadpacket(VtConn *z, uchar score[VtScoreSize],
	36 .br
	37 .B
	38 uint type, int n)
	39 .PP
	40 .B
	41 int vtwritepacket(VtConn *z, uchar score[VtScoreSize],
	42 .br
	43 .B
	44 uint type, Packet *p)
	45 .PP
	46 .B
	47 int vtsync(VtConn *z)
	48 .PP
	49 .B
	50 int vtping(VtConn *z)
	51 .PP
	52 .B
	53 extern int ventidoublechecksha1; /* default 1 */
	54 .SH DESCRIPTION
	55 These routines execute the client side of the
	56 .MR venti (7)
	57 protocol.
	58 .PP
	59 .I Vtrpc
	60 executes a single Venti RPC transaction, sending the request
	61 packet
	62 .IR p
	63 and then waiting for and returning the response packet.
	64 .I Vtrpc
	65 will set the tag in the packet.
	66 .I Vtrpc
	67 frees
	68 .IR p ,
	69 even on error.
	70 .I Vtrpc
	71 is typically called only indirectly, via the functions below.
	72 .PP
	73 .I Vthello
	74 executes a
	75 .B hello
	76 transaction, setting
	77 .IB z ->sid
	78 to the name used by the server.
	79 .I Vthello
	80 is typically called only indirectly, via
	81 .IR vtconnect .
	82 .PP
	83 .I Vtconnect
	84 calls
	85 .I vtversion
	86 (see
	87 .MR venti-conn (3) )
	88 and
	89 .IR vthello ,
	90 in that order, returning success only
	91 if both succeed.
	92 This sequence (calling
	93 .I vtversion
	94 and then
	95 .IR vthello )
	96 must be done before the functions below can be called.
	97 .PP
	98 .I Vtread
	99 reads the block with the given
	100 .I score
	101 and
	102 .I type
	103 from the server,
	104 stores the returned data
	105 in memory at
	106 .IR buf ,
	107 and returns the number of bytes read.
	108 If the server's block has size larger than
	109 .IR n ,
	110 .I vtread
	111 does not modify
	112 .I buf
	113 and
	114 returns an error.
	115 .PP
	116 .I Vtwrite
	117 writes the
	118 .I n
	119 bytes in
	120 .I buf
	121 as a block of the given
	122 .IR type ,
	123 setting
	124 .IR score .
	125 .PP
	126 .I Vtreadpacket
	127 and
	128 .I vtwritepacket
	129 are like
	130 .I vtread
	131 and
	132 .I vtwrite
	133 but return or accept the block contents in the
	134 form of a
	135 .BR Packet .
	136 They avoid making a copy of the data.
	137 .PP
	138 .I Vtsync
	139 causes the server to flush all pending write requests
	140 to disk before returning.
	141 .PP
	142 .I Vtping
	143 executes a ping transaction with the server.
	144 .PP
	145 By default,
	146 .I vtread
	147 and
	148 .I vtreadpacket
	149 check that the SHA1 hash of the returned data
	150 matches the requested
	151 .IR score ,
	152 and
	153 .I vtwrite
	154 and
	155 .I vtwritepacket
	156 check that the returned
	157 .I score
	158 matches the SHA1 hash of the written data.
	159 Setting
	160 .I ventidoublechecksha1
	161 to zero disables these extra checks,
	162 mainly for benchmarking purposes.
	163 Doing so in production code is not recommended.
	164 .PP
	165 These functions can be called from multiple threads
	166 or procs simultaneously to issue requests
	167 in parallel.
	168 Programs that issue requests from multiple threads
	169 in the same proc should start separate procs running
	170 .I vtsendproc
	171 and
	172 .I vtrecvproc
	173 as described in
	174 .MR venti-conn (3) .
	175 .SH SOURCE
	176 .B \*9/src/libventi
	177 .SH SEE ALSO
	178 .MR venti (3) ,
	179 .MR venti-conn (3) ,
	180 .MR venti-packet (3) ,
	181 .MR venti (7)
	182 .SH DIAGNOSTICS
	183 .I Vtrpc
	184 and
	185 .I vtpacket
	186 return nil on error.
	187 The other routines return \-1 on error.
	188 .PP
	189 .I Vtwrite
	190 returns 0 on success: there are no partial writes.