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OSSL_LIB_CTX(3ossl)		    OpenSSL		   OSSL_LIB_CTX(3ossl)

NAME
       OSSL_LIB_CTX, OSSL_LIB_CTX_new, OSSL_LIB_CTX_new_from_dispatch,
       OSSL_LIB_CTX_new_child, OSSL_LIB_CTX_free, OSSL_LIB_CTX_load_config,
       OSSL_LIB_CTX_get0_global_default, OSSL_LIB_CTX_set0_default - OpenSSL
       library context

SYNOPSIS
	#include <openssl/crypto.h>

	typedef	struct ossl_lib_ctx_st OSSL_LIB_CTX;

	OSSL_LIB_CTX *OSSL_LIB_CTX_new(void);
	OSSL_LIB_CTX *OSSL_LIB_CTX_new_from_dispatch(const OSSL_CORE_HANDLE *handle,
						     const OSSL_DISPATCH *in);
	OSSL_LIB_CTX *OSSL_LIB_CTX_new_child(const OSSL_CORE_HANDLE *handle,
					     const OSSL_DISPATCH *in);
	int OSSL_LIB_CTX_load_config(OSSL_LIB_CTX *ctx,	const char *config_file);
	void OSSL_LIB_CTX_free(OSSL_LIB_CTX *ctx);
	OSSL_LIB_CTX *OSSL_LIB_CTX_get0_global_default(void);
	OSSL_LIB_CTX *OSSL_LIB_CTX_set0_default(OSSL_LIB_CTX *ctx);

DESCRIPTION
       OSSL_LIB_CTX is an internal OpenSSL library context type.  Applications
       may allocate their own, but may also use	NULL to	use a default context
       with functions that take	an OSSL_LIB_CTX	argument.

       When a non default library context is in	use care should	be taken with
       multi-threaded applications to properly clean up	thread local resources
       before the OSSL_LIB_CTX is freed.  See OPENSSL_thread_stop_ex(3)	for
       more information.

       OSSL_LIB_CTX_new() creates a new	OpenSSL	library	context.

       OSSL_LIB_CTX_new_from_dispatch()	creates	a new OpenSSL library context
       initialised to use callbacks from the OSSL_DISPATCH structure. This is
       primarily useful	for provider authors. The handle and dispatch
       structure arguments passed should be the	same ones as passed to a
       provider's OSSL_provider_init function. Some OpenSSL functions, such as
       BIO_new_from_core_bio(3), require the library context to	be created in
       this way	in order to work.

       OSSL_LIB_CTX_new_child()	is only	useful to provider authors and does
       the same	thing as OSSL_LIB_CTX_new_from_dispatch() except that it
       additionally links the new library context to the application library
       context.	The new	library	context	is a full library context in its own
       right, but will have all	the same providers available to	it that	are
       available in the	application library context (without having to reload
       them). If the application loads or unloads providers from the
       application library context then	this will be automatically mirrored in
       the child library context.

       In addition providers that are not loaded in the	parent library context
       can be explicitly loaded	into the child library context independently
       from the	parent library context.	Providers loaded independently in this
       way will	not be mirrored	in the parent library context and will not be
       affected	if the parent library context subsequently loads the same
       provider.

       A provider may call the function	OSSL_PROVIDER_load(3) with the child
       library context as required. If the provider already exists due to it
       being mirrored from the parent library context then it will remain
       available and its reference count will be increased. If
       OSSL_PROVIDER_load(3) is	called in this way then
       OSSL_PROVIDER_unload(3) should be subsequently called to	decrement the
       reference count.	OSSL_PROVIDER_unload(3)	must not be called for a
       provider	in the child library context that did not have an earlier
       OSSL_PROVIDER_load(3) call for that provider in that child library
       context.

       In addition to providers, a child library context will also mirror the
       default properties (set via EVP_set_default_properties(3)) from the
       parent library context. If EVP_set_default_properties(3)	is called
       directly	on a child library context then	the new	properties will
       override	anything from the parent library context and mirroring of the
       properties will stop.

       When OSSL_LIB_CTX_new_child() is	called from within the scope of	a
       provider's OSSL_provider_init function the currently initialising
       provider	is not yet available in	the application's library context and
       therefore will similarly	not yet	be available in	the newly constructed
       child library context. As soon as the OSSL_provider_init	function
       returns then the	new provider is	available in the application's library
       context and will	be similarly mirrored in the child library context.

       OSSL_LIB_CTX_load_config() loads	a configuration	file using the given
       "ctx".  This can	be used	to associate a library context with providers
       that are	loaded from a configuration.

       OSSL_LIB_CTX_free() frees the given ctx,	unless it happens to be	the
       default OpenSSL library context.

       OSSL_LIB_CTX_get0_global_default() returns a concrete (non NULL)
       reference to the	global default library context.

       OSSL_LIB_CTX_set0_default() sets	the default OpenSSL library context to
       be ctx in the current thread.  The previous default library context is
       returned.  Care should be taken by the caller to	restore	the previous
       default library context with a subsequent call of this function.	If ctx
       is NULL then no change is made to the default library context, but a
       pointer to the current library context is still returned. On a
       successful call of this function	the returned value will	always be a
       concrete	(non NULL) library context.

       Care should be taken when changing the default library context and
       starting	async jobs (see	ASYNC_start_job(3)), as	the default library
       context when the	job is started will be used throughout the lifetime of
       an async	job, no	matter how the calling thread makes further default
       library context changes in the mean time.  This means that the calling
       thread must not free the	library	context	that was the default at	the
       start of	the async job before that job has finished.

RETURN VALUES
       OSSL_LIB_CTX_new(), OSSL_LIB_CTX_get0_global_default() and
       OSSL_LIB_CTX_set0_default() return a library context pointer on
       success,	or NULL	on error.

       OSSL_LIB_CTX_free() doesn't return any value.

HISTORY
       All of the functions described on this page were	added in OpenSSL 3.0.

COPYRIGHT
       Copyright 2019-2021 The OpenSSL Project Authors.	All Rights Reserved.

       Licensed	under the Apache License 2.0 (the "License").  You may not use
       this file except	in compliance with the License.	 You can obtain	a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.

3.0.2+quic			  2022-03-15		   OSSL_LIB_CTX(3ossl)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | HISTORY | COPYRIGHT

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