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ldap_dup.3

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.TH LDAP_OPEN 3 "2018/03/22" "OpenLDAP 2.4.46"
.\" $OpenLDAP$
.\" Copyright 1998-2018 The OpenLDAP Foundation All Rights Reserved.
.\" Copying restrictions apply.  See COPYRIGHT/LICENSE.
.SH NAME
ldap_dup, ldap_destroy, \- Duplicate and destroy LDAP session handles
.SH LIBRARY
OpenLDAP LDAP (libldap, \-lldap)
.SH SYNOPSIS
.nf
.ft B
#include <ldap.h>
.LP
.ft B
LDAP *ldap_dup(
.RS
.ft B
LDAP *\fIold\fB );
.RE
.LP
.ft B
int ldap_destroy(
.RS
.ft B
LDAP *\fIold\fB );
.RE
.SH DESCRIPTION
.LP
.B ldap_dup()
duplicates an existing LDAP
.RB ( "LDAP *" )
session handle.
The new session handle may be used concurrently with the
original session handle.
In a threaded environment, different threads may execute concurrent
requests on the same connection/session without fear of contamination.
Each session handle manages its own private error results.
.LP
.B ldap_destroy()
destroys an existing session handle.
.LP
The
.B ldap_dup()
and
.B ldap_destroy()
functions are used in conjunction with a "thread safe" version
of
.B libldap
.RB ( libldap_r )
to enable operation thread safe API calls, so that a single session
may be simultaneously used across multiple threads with consistent
error handling.
.LP
When a session is created through the use of one of the session creation
functions including
.BR ldap_open (3),
.BR ldap_init (3),
.BR ldap_initialize (3)
or
.BR ldap_init_fd (3)
an
.B "LDAP *"
session handle is returned to the application.
The session handle may be shared amongst threads, however the
error codes are unique to a session handle.
Multiple threads performing different operations using the same
session handle will result in inconsistent error codes and
return values.
.LP
To prevent this confusion,
.B ldap_dup()
is used duplicate an existing session handle so that multiple threads
can share the session, and maintain consistent error information
and results.
.LP
The message queues for a session are shared between sibling session handles.
Results of operations on a sibling session handles are accessible
to all the sibling session handles.
Applications desiring results associated with a specific operation
should provide the appropriate msgid to
.BR ldap_result() .
Applications should avoid calling
.B ldap_result()
with
.B LDAP_RES_ANY
as that may "steal" and return results in the calling thread
that another operation in a different thread, using a
different session handle, may require to complete.
.LP
When
.B ldap_unbind()
is called on a session handle with siblings, all the 
siblings become invalid.
.LP
Siblings must be destroyed using
.BR ldap_destroy() .
Session handle resources associated with the original
.RB ( "LDAP *" )
will be freed when the last session handle is destroyed or when
.B ldap_unbind()
is called, if no other session handles currently exist.
.SH ERRORS
If an error occurs,
.B ldap_dup()
will return NULL and 
.I errno
should be set appropriately.
.B ldap_destroy()
will directly return the LDAP code associated to the error (or
.I LDAP_SUCCESS
in case of success);
.I errno
should be set as well whenever appropriate.
.SH SEE ALSO
.BR ldap_open (3),
.BR ldap_init (3),
.BR ldap_initialize (3),
.BR ldap_init_fd (3),
.BR errno (3)
.SH ACKNOWLEDGEMENTS
This work is based on the previously proposed
.B LDAP C API Concurrency Extensions
draft
.BR ( draft-zeilenga-ldap-c-api-concurrency-00.txt )
effort.
.lf 1 ./../Project
.\" Shared Project Acknowledgement Text
.B "OpenLDAP Software"
is developed and maintained by The OpenLDAP Project <http://www.openldap.org/>.
.B "OpenLDAP Software"
is derived from the University of Michigan LDAP 3.3 Release.  
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