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.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

resoponds 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)