.\"	$NetBSD: puffs_cc.3,v 1.6 2007/05/06 13:56:16 pooka Exp $
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.Dd April 19, 2007
.Dt PUFFS_CC 3
.Os
.Sh NAME
.Nm puffs_cc
.Nd puffs continuation routines
.Sh LIBRARY
.Lb libpuffs
.Sh SYNOPSIS
.In puffs.h
.Ft struct puffs_usermount *
.Fn puffs_cc_getusermount "struct puffs_cc *pcc"
.Ft void *
.Fn puffs_cc_getspecific "struct puffs_cc *pcc"
.Ft void
.Fn puffs_cc_yield "struct puffs_cc *pcc"
.Ft void
.Fn puffs_cc_continue "struct puffs_cc *pcc"
.Ft int
.Fn puffs_docc "struct puffs_cc *pcc" "struct puffs_putreq *ppr"
.Sh DESCRIPTION
.Em IMPORTANT NOTE!
This document describes interfaces which are not yet guaranteed to be
stable.
In case you update your system sources, please recompile everything
and fix complation errors.
If your sources are out-of-sync, incorrect operation may result.
The interfaces in this document will most likely be hugely simplified
in later versions or made transparent to the implementation.
.Pp
These functions enable the use of continuations within the framework.
Every operation callback within a file system implementation is
automatically passed an opaque cookie,
.Va pcc ,
to be used as a continuation handle.
.Pp
File systems using continuations should define their own event loop
instead of using
.Fn puffs_mainloop .
.Pp
.Bl -tag -width xxxx
.It Fn puffs_cc_getusermount "pcc"
Returns a pointer to the file system structure
.Va struct puffs_usermount
the context is associated with.
.It Fn puffs_cc_getspecific "pcc"
Returns a pointer to file system private data.
This is shorthand for
calling
.Fn puffs_getspecific
with the result from
.Fn puffs_cc_getusermount .
.It Fn puffs_cc_yield "pcc"
Suspend and save the current execution context and return control
to the previous point.
In practice, from the file system author perspective, control returns
back to where either
.Fn puffs_req_handle
or
.Fn puffs_docc
was called.
.It Fn puffs_cc_continue pcc
Will suspend current execution and return control to where it was
before before calling
.Fn puffs_cc_yield .
This is rarely called directly.
.It Fn puffs_docc "pcc" "ppr"
Continues request suspended with
.Fn puffs_cc_yield .
If the request completes without yielding again, the result can be
found from
.Fa ppr .
.El
.Pp
Before calling
.Fn puffs_cc_yield
a file system will typically want to record some cookie value into its
own internal bookkeeping.
This cookie should be hooked to the
.Va pcc
so that the correct continuation can be continued when the event it
was waiting for triggers.
.Pp
The puffs ssh file system is supposed to be the canonical example
for the use of the continuation framework.
.Sh SEE ALSO
.Xr puffs 3 ,
.Xr puffs_framebuf 3 ,
.Xr puffs_req 3 ,
.Xr mount_psshfs 8