.TH 9PFID 2
.SH NAME
Fid, Fidpool, allocfidpool, freefidpool, allocfid, closefid, lookupfid, removefid,
Req, Reqpool, allocreqpool, freereqpool, allocreq, closereq, lookupreq, removereq \- 9P fid, request tracking
.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'\fL    'u +\w'\fLulong 'u
typedef struct Fid
{
	ulong	fid;
	char	omode;  /* -1 if not open */
	char	*uid;
	Qid	qid;
	File	*file;
	void	*aux;
	\fI...\fP
} Fid;
.fi
.PP
.ft L
.nf
.ta \w'\fL    'u +\w'\fLulong 'u
typedef struct Req
{
	ulong	tag;
	Fcall	ifcall;
	Fcall	ofcall;
	Req	*oldreq;
	void	*aux;
	Fid	*fid;
	Fid	*afid;
	Fid	*newfid;
	\fI...\fP
} Req;
.fi
.PP
.ft L
.nf
.ta \w'\fLFidpool* 'u
Fidpool*	allocfidpool(void (*destroy)(Fid*))
void	freefidpool(Fidpool *p)
Fid*	allocfid(Fidpool *p, ulong fid)
Fid*	lookupfid(Fidpool *p, ulong fid)
Fid*	removefid(Fidpool *p, ulong fid);
void	closefid(Fid *f)
.fi
.PP
.ft L
.nf
.ta \w'\fLReqpool* 'u
Reqpool*	allocreqpool(void (*destroy)(Req*))
void	freereqpool(Reqpool *p)
Req*	allocreq(Reqpool *p, ulong tag)
Req*	lookupreq(Reqpool *p, ulong tag)
Req*	removereq(Reqpool *p, ulong tag);
void	closereq(Req *f)
.fi
.SH DESCRIPTION
These routines provide management of 
.B Fid
and
.B Req
structures from 
.BR Fidpool s
and
.BR Reqpool s.
They are primarily used by the 9P server loop
described in 
.IR 9p (2).
.PP
.B Fid
structures are intended to represent
active fids in a 9P connection, as 
.B Chan
structures do in the Plan 9 kernel.
The
.B fid
element is the integer fid used in the 9P 
connection.
.B Omode
is the mode under which the fid was opened, or 
.B -1 
if this fid has not been opened yet.
Note that in addition to the values 
.BR OREAD ,
.BR OWRITE ,
and
.BR ORDWR ,
.B omode
can contain the various flags permissible in
an open call.
To ignore the flags, use
.BR omode&OMASK .
.B Omode
should not be changed by the client.
The fid derives from a successful authentication by
.BR uid .
.B Qid
contains the qid returned in the last successful
.B walk
or
.B create
transaction involving the fid.
In a file tree-based server, the 
.BR Fid 's
.B file
element points at a
.B File
structure 
(see
.IR 9pfile (2))
corresponding to the fid.
The
.B aux
member is intended for use by the
client to hold information specific to a particular
.BR Fid .
With the exception of 
.BR aux ,
these elements should be treated
as read-only by the client.
.PP
.I Allocfidpool
creates a new 
.BR Fidpool .
.I Freefidpool
destroys such a pool.
.I Allocfid
returns a new
.B Fid
whose fid number is
.IR fid .
There must not already be an extant
.B Fid
with that number in the pool.
Once a 
.B Fid
has been allocated, it can be looked up by 
fid number using
.IR lookupfid .
.BR Fid s
are reference counted: both 
.I allocfid
and
.I lookupfid
increment the reference count on the 
.B Fid
structure before
returning.
When a reference to a 
.B Fid
is no longer needed, 
.I closefid
should be called to note the destruction of the reference.
When the last reference to a 
.B Fid
is removed, if
.I destroy
(supplied when creating the fid pool)
is not zero, it is called with the 
.B Fid
as a parameter.
It should perform whatever cleanup is necessary
regarding the
.B aux
element.
.I Removefid
is equivalent to
.I lookupfid
but also removes the
.B Fid
from the pool.
Note that due to lingering references,
the return of
.I removefid
may not mean that
.I destroy
has been called.
.PP
.IR Allocreqpool ,
.IR freereqpool ,
.IR allocreq ,
.IR lookupreq ,
.IR closereq ,
and
.I removereq
are analogous but
operate on 
.BR Reqpool s
and
.B Req
structures.
.SH SOURCE
.B /sys/src/lib9p
.SH SEE ALSO
.IR 9p (2),
.IR 9pfile (2)