\"      $NetBSD: tss.3,v 1.2 2019/04/27 10:57:11 wiz Exp $
\"
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\" All rights reserved.
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\" This code is derived from software contributed to The NetBSD Foundation
\" by Kamil Rytarowski.
\"
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Dd October 16, 2016
Dt TSS 3
Os
Sh NAME
Nm tss
Nd thread-specific storage functions
Sh LIBRARY
Lb libpthread
Sh SYNOPSIS
In threads.h
Vt "typedef" "void" "(*tss_dtor_t)" "(void *)"
Ft int
Fn tss_create "tss_t *key" "tss_dtor_t dtor"
Ft void
Fn tss_delete "tss_t key"
Ft void *
Fn tss_get "tss_t key"
Ft int
Fn tss_set "tss_t key" "void *val"
Vt #define TSS_DTOR_ITERATIONS /* implementation specified */
Sh DESCRIPTION
There are two groups of storage in C programs:
Bl -dash
It
local storage,
It
global storage.
El
Pp
Multithreaded programs in C add the third group
Sy thread-specific storage .
This data is private to thread and every entry of this type has an associated
Dv tss_t
opaque key that is global to all threads in the process.
A thread using the
Dv tss_t *
pointer accesses private data.
Pp
The
Fn tss_create
function creates a thread-specific storage with the
Fa key
handler with optional destructor
Fa dtor .
If the
Fa dtor
parameter is not
Dv NULL ,
then specified appropriate destructor will be called on thread termination.
The destructor is not called if a thread called the
Fn tss_delete
function for the specified
Fa key .
If, after all the destructors have been called for all
Pf non- Dv NULL
values with associated destructors,
there are still some
Pf non- Dv NULL
values with associated destructors,
then the process is repeated.
If, after at least
Dv TSS_DTOR_ITERATIONS
iterations of destructor calls for outstanding
Pf non- Dv NULL
values, there are still some
Pf non- Dv NULL
values with associated destructors, the
Nx
implementation stops calling further destructors.
The
Xr thrd_exit 3
function must not be called from a destructor.
Pp
The
Fn tss_delete
function frees resources used by the thread-specific storage identified by the
Fa key
object.
This function can be called inside the
Fa dtor
destructor, however the destructor is not called by
Fn tss_delete .
Pp
The
Fn tss_get
and
Fn tss_set
functions are used to get and set thread-specific storage.
Sh RETURN VALUES
The
Fn tss_create
function returns
Dv thrd_success
on success, otherwise
Dv thrd_error
on failure.
Pp
The
Fn tss_delete
function returns no value.
Pp
The
Fn tss_get
returns pointer to thread-specific storage on success or
Dv NULL
on failure.
Pp
The
Fn tss_set
function returns
Dv thrd_success
on success, otherwise
Dv thrd_error
on failure.
Sh SEE ALSO
Xr pthread_getspecific 3 ,
Xr pthread_key_create 3 ,
Xr threads 3
Sh STANDARDS
The
Nm
interface conforms to
St -isoC-2011 .
Sh HISTORY
This interface first appeared in
Nx 9 .
Sh AUTHORS
An Kamil Rytarowski Aq Mt [email protected]

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