term% cat index.txt FCALL(2) System Calls Manual FCALL(2)
NAME
Fcall, convS2M, convD2M, convM2S, convM2D, getS, fcallconv, dirconv,
dirmodeconv - interface to Plan 9 File protocol
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <auth.h>
#include <fcall.h>
int convS2M(Fcall *f, char *ap)
int convD2M(Dir *d, char *ap)
int convM2S(char *ap, Fcall *f, int n)
int convM2D(char *ap, Dir *d)
char *getS(int fd, char *ap, Fcall *f, long *lp)
int dirconv(void *o, Fconv*)
int fcallconv(void *o, Fconv*)
int dirmodeconv(void *o, Fconv*)
DESCRIPTION
These routines convert messages in the machine-independent format of
the Plan 9 file protocol, 9P, to and from a more convenient form, an
Fcall structure:
typedef
struct Fcall {
char type;
short fid;
short tag;
union {
struct {
ushort oldtag;/* Tflush */
Qid qid; /* Rattach, Rwalk,
Ropen, Rcreate */
char rauth[AUTHENTLEN]; /* Rattach */
};
struct {
char uname[NAMELEN]; /* Tattach */
char aname[NAMELEN]; /* Tattach */
char ticket[TICKETLEN]; /* Tattach */
char auth[AUTHENTLEN]; /* Tattach */
};
struct {
char ename[ERRLEN]; /* Rerror */
char authid[NAMELEN]; /* Rsession */
char authdom[DOMLEN]; /* Rsession */
char chal[CHALLEN]; /* Tsession/Rsession */
};
struct {
long perm; /* Tcreate */
short newfid; /* Tclone, Tclwalk */
char name[NAMELEN]; /* Twalk, Tclwalk,
Tcreate */
char mode; /* Tcreate, Topen */
};
struct {
long offset; /* Tread, Twrite */
long count; /* Tread, Twrite, Rread */
char *data; /* Twrite, Rread */
};
struct {
char stat[DIRLEN]; /* Twstat, Rstat */
};
};
} Fcall;
This structure is defined in <fcall.h>. See section 5 for a full de‐
scription of 9P messages and their encoding. For all message types,
the type field of an Fcall holds one of Tnop, Rnop, Tsession, Rsession,
etc. (defined in an enumerated type in <fcall.h>). Fid is used by most
messages, and tag is used by all messages. The other fields are used
selectively by the message types given in comments.
ConvM2S takes a 9P message at ap of length n, and uses it to fill in
Fcall structure f. If the passed message including any data for Twrite
and Rread messages is formatted properly, the return value is n; other‐
wise it is 0. For Twrite and Tread messages, data is set to a pointer
into the argument message, not a copy.
ConvS2M does the reverse conversion, turning f into a message starting
at ap. The length of the resulting message is returned. For Twrite
and Rread messages, count bytes starting at data are copied into the
message.
The constant MAXMSG is the length of the longest message, excluding
data; MAXFDATA (8192) is the maximum count in a read or write message.
Thus messages are guaranteed to be shorter than MAXMSG+MAXFDATA bytes
long.
Another structure is Dir, used by the routines described in stat(2).
ConvM2D converts the machine-independent form starting at ap into d and
returns the length of the encoding. ConvD2M does the reverse transla‐
tion, also returning the length of the encoding.
GetS reads a message from file descriptor fd into ap and converts the
message using convM2S into the Fcall structure f. The lp argument must
point to a long holding the size of the ap buffer. It is somewhat re‐
silient to transient read errors. If convM2S succeeds, its return
value is stored in *lp, and getS returns zero. Otherwise getS returns
a string identifying the error.
Dirconv, fcallconv, and dirmodeconv are formatting routines, suitable
for fmtinstall (see print(2)). They convert Dir*, Fcall*, and long
values into string representations of the directory buffer, Fcall buf‐
fer, or file mode value. Fcallconv assumes that dirconv has been in‐
stalled with format letter
SOURCE
/sys/src/libc/9sys
SEE ALSO
intro(2), stat(2), intro(5)
DIAGNOSTICS
GetS sets errstr.
BUGS
The offset and directory length fields have 8 bytes in the protocol,
but these routines assume they fit into a long.
ConvS2M should check for counts exceeding MAXFMSG.
FCALL(2)