9PCMDBUF(2)9PCMDBUF(2)
NAME
Cmdbuf, parsecmd, respondcmderror, lookupcmd – control message parsing
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <fcall.h>
#include <thread.h>
#include <9p.h>
typedef struct Cmdbuf
{
char *buf;
char **f;
int nf;
} Cmdbuf;
typedef struct Cmdtab
{
int index;
char *cmd;
int narg;
};
Cmdbuf *parsecmd(char *p, int n)
Cmdtab *lookupcmd(Cmdbuf *cb, Cmdtab *tab, int ntab)
void respondcmderror(Req *r, Cmdbuf *cb, char *fmt, ...)
DESCRIPTION
These data structures and functions provide parsing of textual control messages.
Parsecmd
treats the
n
bytes at
p
(which need not be NUL-terminated) as a UTF string and splits it
using
tokenize
(see
getfields(2)).
It returns a
Cmdbuf
structure holding pointers to each field in the message.
It is the caller’s responsibility to
free this structure when it is no longer needed.
Lookupcmd
walks through the array
ctab,
which has
ntab
entries,
looking for the first
Cmdtab
that matches the parsed command.
(If the parsed command is empty,
lookupcmd
returns nil immediately.)
A
Cmdtab
matches the command if
cmd
is equal to
cb->f[0]
or if
cmd
is
*.
Once a matching
Cmdtab
has been found, if
narg
is not zero, then the parsed command
must have exactly
narg
fields (including the command string itself).
If the command has the wrong number of arguments,
lookupcmd
returns nil.
Otherwise, it returns a pointer to the
Cmdtab
entry.
If
lookupcmd
does not find a matching command at all,
it returns nil.
Whenever
lookupcmd
returns nil, it sets the system error string.
Respondcmderror
responds to request
r
with an error of the form
‘fmt: cmd,’
where
fmt
is the formatted string and
cmd
is a reconstruction of the parsed command.
Fmt
is often simply
%r .
EXAMPLES
This interface is not used in any distributed 9P servers.
It was lifted from the Plan 9 kernel.
Almost any kernel driver
(/sys/src/9/*/dev*.c)
is a good example.
SOURCE
/sys/src/lib9p/parse.c
SEE
9p(2)