TH 9PCMDBUF 2
SH NAME
Cmdbuf, parsecmd, respondcmderror, lookupcmd \- control message parsing
SH SYNOPSIS
ft L
nf
#include <u.h>
#include <libc.h>
#include <fcall.h>
#include <thread.h>
#include <9p.h>
fi
PP
ft L
nf
ta \w'\fL1234'u +\w'\fL12345678'u
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, ...)
fi
SH DESCRIPTION
These data structures and functions provide parsing of textual control messages.
PP
I Parsecmd
treats the
I n
bytes at
I p
(which need not be NUL-terminated) as a UTF string and splits it
using
I tokenize
(see
IR getfields (2)).
It returns a
B 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.
PP
I Lookupcmd
walks through the array
IR ctab ,
which has
I ntab
entries,
looking for the first
B Cmdtab
that matches the parsed command.
(If the parsed command is empty,
I lookupcmd
returns nil immediately.)
A
B Cmdtab
matches the command if
I cmd
is equal to
IB cb -> f [0]
or if
I cmd
is
LR * .
Once a matching
B Cmdtab
has been found, if
I narg
is not zero, then the parsed command
must have exactly
I narg
fields (including the command string itself).
If the command has the wrong number of arguments,
I lookupcmd
returns nil.
Otherwise, it returns a pointer to the
B Cmdtab
entry.
If
I lookupcmd
does not find a matching command at all,
it returns nil.
Whenever
I lookupcmd
returns nil, it sets the system error string.
PP
I Respondcmderror
responds to request
I r
with an error of the form
`\fIfmt\fB:\fI cmd\fR,'
where
I fmt
is the formatted string and
I cmd
is a reconstruction of the parsed command.
Fmt
is often simply
B "%r" .
SH EXAMPLES
This interface is not used in any distributed 9P servers.
It was lifted from the Plan 9 kernel.
Almost any kernel driver
RB ( /sys/src/9/*/dev*.c )
is a good example.
SH SOURCE
B /sys/src/lib9p/parse.c
SH SEE ALSO
IR 9p (2)
