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.\" Copyright (c) 2001-2002 Packet Design, LLC.
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.\" 
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.\" Author: Archie Cobbs <archie@freebsd.org>
.\"
.\" $Id: tinfo.3,v 1.1 2012/02/21 23:25:53 misho Exp $
.\"
.Dd April 22, 2002
.Dt TINFO 3
.Os
.Sh NAME
.Nm tinfo
.Nd self-(de)allocating thread-local data structures
.Sh LIBRARY
PDEL Library (libpdel, \-lpdel)
.Sh SYNOPSIS
.In pthread.h
.In pdel/util/tinfo.h
.Fn TINFO_INIT type mtype initfunc
.Ft "void *"
.Fn tinfo_get "struct tinfo *t"
.Ft "int"
.Fn tinfo_set "struct tinfo *t" "const void *data"
.Ft "int"
.Fn tinfo_set_nocopy "struct tinfo *t" "void *data"
.Sh DESCRIPTION
These functions provide support for thread-local data structures defined by
.Xr structs 3
types that are automatically initialized and destroyed.
A thread-local data structure is described by a static or global
.Li "struct tinfo" ;
each such structure must be initialized with the
.Fn TINFO_INIT
macro.
For example:
.Pp
.Bd -literal -compact -offset 3n
static struct tinfo foo_info
        = TINFO_INIT(&foo_type, "foo", fooinit);
.Ed
.Pp
.Fa type
is the
.Xr structs 3
type for the data structure,
.Fa mtype
is the
.Xr typed_mem 3
type used to allocate memory to hold each thread's instance, and
.Fa initfunc
is an optional instance initializer function of this type:
.Pp
.Bd -literal -compact -offset 3n
typedef int tinfo_init_t(struct tinfo *t, void *data);
.Ed
.Pp
.Fn initfunc
should initialize the data structure pointed to by
.Fa data
as an instance of
.Fa type
(which will also be available as
.Fa "t->type") .
The memory pointed to by
.Fa data
will have been allocated with
.Xr typed_mem 3
type
.Fa mtype
but will be otherwise uninitialized.
If
.Fa initfunc
is
.Dv NULL ,
then
.Xr structs_init 3
is used to initialize the data structure to the default value defined by
.Fa type .
.Pp
Instances of
.Nm tinfo
thread-local data structure are automatically destroyed when the associated
thread exits, by calling
.Fn structs_free type NULL data
and then
.Fn FREE mtype data .
.Pp
.Fn tinfo_get
returns the current thread's instance of the data structure.
If this is the thread's first invocation of
.Fn tinfo_get ,
a new instance is automatically allocated and initialized.
The caller should
.En not
free the returned value, but may modify it in a way consistent
with its
.Xr structs 3
type.
.Pp
.Fn tinfo_set
sets the current thread's data structure instance to be a copy of
.Fa data ,
made using
.Xr structs_get 3 .
The original
.Fa data
is unmodified and remains the caller's responsibility to free.
Any existing thread-local data structure instance is automatically
replaced and freed.
.Pp
.Fn tinfo_set_nocopy
is equivalent to
.Fn tinfo_set
except that no copy of
.Fa data
is made; therefore,
.Fa data
must point to heap memory allocated with
.Xr typed_mem 3
type
.Fa "mtype"
(also available as
.Fa "t->mtype")
and the caller should not dereference
.Fa data
once
.Fn tinfo_set_nocopy
has returned successfully.
.Pp
Both
.Fn tinfo_set
and
.Fn tinfo_set_nocopy
may take a
.Dv NULL
.Fa data
parameter; this causes any existing thread-local data structure instance
to be freed so that the next call to
.Fn tinfo_get
will cause a new instance to be constructed.
.Sh RETURN VALUES
.Fn tinfo_get ,
.Fn tinfo_set ,
and
.Fn tinfo_set_nocopy
return
.Dv NULL
or -1 with
.Va errno
set appropriately to indicate an error.
.Sh SEE ALSO
.Xr libpdel 3 ,
.Xr structs 3 ,
.Xr typed_mem 3
.Sh HISTORY
The PDEL library was developed at Packet Design, LLC.
.Dv "http://www.packetdesign.com/"
.Sh AUTHORS
.An Archie Cobbs Aq archie@freebsd.org