VENTI-FCALL(2)                                     VENTI-FCALL(2)

     NAME
          VtEntry, VtFcall, VtRoot, vtentrypack, vtentryunpack,
          vtfcallclear, vtfcallfmt, vtfcallpack, vtfcallunpack,
          vtfromdisktype, vttodisktype, vtgetstring, vtputstring,
          vtrootpack, vtrootunpack, vtparsescore, vtscorefmt - venti
          data formats

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

          enum
          {
              VtEntrySize = 40,
              VtRootSize = 300,
              VtScoreSize = 20,
          };

          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;

          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;

          void    vtentrypack(VtEntry *e, uchar *buf, int index)
          int     vtentryunpack(VtEntry *e, uchar *buf, int index)

          Packet* vtfcallpack(VtFcall *f)
          int     vtfcallunpack(VtFcall *f, Packet *p)

          void vtfcallclear(VtFcall *f)

          uint    vttodisktype(uint type)
          uint    vtfromdisktype(uint type)

     VENTI-FCALL(2)                                     VENTI-FCALL(2)

          int     vtputstring(Packet *p, char *s)
          int     vtgetstring(Packet *p, char **s)

          void    vtrootpack(VtRoot *r, uchar *buf)
          int     vtrootunpack(VtRoot *r, uchar *buf)

          int     vtparsescore(char *s, char **prefix, uchar score[VtScoreSize])

          int     vtfcallfmt(Fmt *fmt)
          int     vtscorefmt(Fmt *fmt)

     DESCRIPTION
          These routines convert between C representations of Venti
          structures and serialized representations used on disk and
          on the network.

          Vtentrypack converts a VtEntry structure describing a Venti
          file (see venti(6)) into a 40-byte (VtEntrySize) structure
          at buf+index*40.  Vtentryunpack does the reverse conversion.

          Vtfcallpack converts a VtFcall structure describing a Venti
          protocol message (see venti(6)) into a packet.
          Vtfcallunpack does the reverse conversion.

          The fields in a VtFcall are named after the protocol fields
          described in venti(6), except that the type field is renamed
          blocktype.  The msgtype field holds the one-byte message
          type: VtThello, VtRhello, and so on.

          Vtfcallclear frees the strings f->error, f->version, f->uid,
          f->sid, the buffers f->crypto and f->codec, and the packet
          f->data.

          The block type enumeration defined in <venti.h> (presented
          in 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
          VtDataType+n and VtDirType+n blocks.  Vttodisktype converts
          a <venti.h> enumeration value to the disk value;
          vtfromdisktype converts a disk value to the enumeration
          value, always using the VtDirType pointers.  The VtFcall
          field blocktype is an enumeration value (vtfcallpack and
          vtfcallunpack convert to and from the disk values used in
          packets automatically), so most programs will not need to
          call these functions.

          Vtputstring appends the Venti protocol representation of the
          string s to the packet p. Vtgetstring reads a string from
          the packet, returning a pointer to a copy of the string in
          *s.  The copy must be freed by the caller.  These functions
          are used by vtfcallpack and vtfcallunpack; most programs
          will not need to call them directly.

     VENTI-FCALL(2)                                     VENTI-FCALL(2)

          Vtrootpack converts a VtRoot structure describing a Venti
          file tree into the 300-byte (VtRootSize) buffer pointed to
          by buf. Vtrootunpack does the reverse conversion.

          Vtparsescore parses the 40-digit hexadecimal string s, writ-
          ing its value into score. If the hexadecimal string is pre-
          fixed with a text label followed by a colon, a copy of that
          label is returned in *prefix.  If prefix is nil, the label
          is ignored.

          Vtfcallfmt and vtscorefmt are print(2) formatters to print
          VtFcall structures and scores.  Vtfcallfmt assumes that
          vtscorefmt is installed as %V.

     SOURCE
          /sys/src/libventi

     SEE ALSO
          venti(1), venti(2), venti(6)

     DIAGNOSTICS
          Vtentrypack, vtfcallpack, vtrootpack, and vtfcallclear can-
          not fail.

          Vtentryunpack, vtrootunpack, vtputstring, vtgetstring, and
          vtparsescore return 0 on success, -1 on error.

          Vtfcallpack returns a packet on success, nil on error.

          Vttodisktype and vtfromdisktype return VtCorruptType (255)
          when presented with invalid input.