.TH VENTI-FCALL 2
.SH NAME
VtEntry, VtFcall, VtRoot,
vtentrypack,
vtentryunpack,
vtfcallclear,
vtfcallfmt,
vtfcallpack,
vtfcallunpack,
vtfromdisktype,
vttodisktype,
vtgetstring,
vtputstring,
vtrootpack,
vtrootunpack,
vtparsescore,
vtscorefmt \- venti data formats
.SH SYNOPSIS
.PP
.ft L
#include <u.h>
.br
#include <libc.h>
.br
#include <venti.h>
.ta +\w'\fLxxxx'u
.PP
.ft L
.nf
enum
{
	VtEntrySize = 40,
	VtRootSize = 300,
	VtScoreSize = 20,
};
.PP
.ft L
.nf
typedef struct VtEntry
{
	ulong gen;    /* generation number */
	ushort psize;   /* pointer block size */
	ushort dsize;   /* data block size */
	uchar type;
	uchar flags;
	uvlong size;
	uchar score[VtScoreSize];
} VtEntry;
.PP
.ft L
.nf
typedef struct VtRoot
{
	char name[128];
	char type[128];
	uchar score[VtScoreSize];  /* to a Dir block */
	ushort blocksize;          /* maximum block size */
	uchar prev[VtScoreSize];   /* previous root block */
} VtRoot;
.ta +\w'\fLPacket* 'u
.PP
.B
void	vtentrypack(VtEntry *e, uchar *buf, int index)
.br
.B
int	vtentryunpack(VtEntry *e, uchar *buf, int index)
.PP
.B
Packet*	vtfcallpack(VtFcall *f)
.br
.B
int	vtfcallunpack(VtFcall *f, Packet *p)
.PP
.B
void vtfcallclear(VtFcall *f)
.PP
.B
uint	vttodisktype(uint type)
.br
.B
uint	vtfromdisktype(uint type)
.PP
.B
int	vtputstring(Packet *p, char *s)
.br
.B
int	vtgetstring(Packet *p, char **s)
.PP
.B
void	vtrootpack(VtRoot *r, uchar *buf)
.br
.B
int	vtrootunpack(VtRoot *r, uchar *buf)
.PP
.B
int	vtparsescore(char *s, char **prefix, uchar score[VtScoreSize])
.PP
.B
int	vtfcallfmt(Fmt *fmt)
.B
int	vtscorefmt(Fmt *fmt)
.SH DESCRIPTION
These routines convert between C representations of Venti
structures and serialized representations used on disk and
on the network.
.PP
.I Vtentrypack
converts a
.B VtEntry
structure describing a Venti file
(see
.IR venti (6))
into a 40-byte
.RB ( VtEntrySize )
structure at
.IB buf + index *40 \fR.
Vtentryunpack
does the reverse conversion.
.PP
.I Vtfcallpack
converts a
.B VtFcall
structure describing a Venti protocol message
(see
.IR venti (6))
into a packet.
.I Vtfcallunpack
does the reverse conversion.
.PP
The fields in a
.B VtFcall
are named after the protocol fields described in
.IR venti (6),
except that the
.B type
field is renamed
.BR blocktype .
The
.B msgtype
field holds the one-byte message type:
.BR VtThello ,
.BR VtRhello ,
and so on.
.PP
.I Vtfcallclear
frees the strings
.IB f ->error \fR,
.IB f ->version \fR,
.IB f ->uid \fR,
.IB f ->sid \fR,
the buffers
.IB f ->crypto
and
.IB f ->codec \fR,
and the packet
.IB f ->data \fR.
.PP
The block type enumeration defined in
.B <venti.h>
(presented in 
.IR venti (6))
differs from the one used on disk and in the network
protocol.
The disk and network representation uses different
constants and does not distinguish between
.BI VtDataType+ n
and
.BI VtDirType+ n
blocks.
.I Vttodisktype
converts a
.B <venti.h>
enumeration value to the disk value;
.I vtfromdisktype
converts a disk value to the enumeration value,
always using the
.B VtDirType
pointers.
The
.B VtFcall
field
.B blocktype
is an enumeration value
.RI ( vtfcallpack
and
.I vtfcallunpack
convert to and from the disk values used in packets
automatically),
so most programs will not need to call these functions.
.PP
.I Vtputstring
appends the Venti protocol representation of the string
.I s
to the packet
.IR p .
.I Vtgetstring
reads a string from the packet, returning a pointer to a copy
of the string in
.BI * s \fR.
The copy must be freed by the caller.
These functions are used by
.I vtfcallpack
and
.IR vtfcallunpack ;
most programs will not need to call them directly.
.PP
.I Vtrootpack
converts a
.B VtRoot
structure describing a Venti file tree
into the 300-byte 
.RB ( VtRootSize )
buffer pointed to by
.IR buf .
.I Vtrootunpack does the reverse conversion.
.PP
.I Vtparsescore
parses the 40-digit hexadecimal string
.IR s ,
writing its value
into
.IR score .
If the hexadecimal string is prefixed with
a text label followed by a colon, a copy of that
label is returned in
.BI * prefix \fR.
If
.I prefix
is nil, the label is ignored.
.PP
.I Vtfcallfmt
and
.I vtscorefmt
are
.IR print (2)
formatters to print
.B VtFcall
structures and scores.
.I Vtfcallfmt
assumes that
.I vtscorefmt
is installed as
.BR %V .
.SH SOURCE
.B /sys/src/libventi
.SH SEE ALSO
.IR venti (1),
.IR venti (2),
.IR venti (6)
.SH DIAGNOSTICS
.IR Vtentrypack ,
.IR vtfcallpack ,
.IR vtrootpack ,
and
.I vtfcallclear
cannot fail.
.PP
.IR Vtentryunpack ,
.IR vtrootunpack ,
.IR vtputstring ,
.IR vtgetstring ,
and
.I vtparsescore
return 0 on success, \-1 on error.
.PP
.I Vtfcallpack
returns a packet on success, nil on error.
.PP
.I Vttodisktype
and
.I vtfromdisktype
return
.B VtCorruptType
(255)
when presented with invalid input.