=pod

=head1 NAME

OSSL_STORE_LOADER, OSSL_STORE_LOADER_CTX, OSSL_STORE_LOADER_new,

OSSL_STORE_LOADER_get0_engine, OSSL_STORE_LOADER_get0_scheme,

OSSL_STORE_LOADER_set_open, OSSL_STORE_LOADER_set_ctrl,

OSSL_STORE_LOADER_set_expect, OSSL_STORE_LOADER_set_find,

OSSL_STORE_LOADER_set_load, OSSL_STORE_LOADER_set_eof,

OSSL_STORE_LOADER_set_error, OSSL_STORE_LOADER_set_close,

OSSL_STORE_LOADER_free, OSSL_STORE_register_loader,

OSSL_STORE_unregister_loader, OSSL_STORE_open_fn, OSSL_STORE_ctrl_fn,

OSSL_STORE_expect_fn, OSSL_STORE_find_fn,

OSSL_STORE_load_fn, OSSL_STORE_eof_fn, OSSL_STORE_error_fn,

OSSL_STORE_close_fn - Types and functions to manipulate, register and

unregister STORE loaders for different URI schemes

=head1 SYNOPSIS

 #include <openssl/store.h>

 typedef struct ossl_store_loader_st OSSL_STORE_LOADER;

 OSSL_STORE_LOADER *OSSL_STORE_LOADER_new(ENGINE *e, const char *scheme);

 const ENGINE *OSSL_STORE_LOADER_get0_engine(const OSSL_STORE_LOADER

                                             *store_loader);

 const char *OSSL_STORE_LOADER_get0_scheme(const OSSL_STORE_LOADER

                                           *store_loader);

 /* struct ossl_store_loader_ctx_st is defined differently by each loader */

 typedef struct ossl_store_loader_ctx_st OSSL_STORE_LOADER_CTX;

 typedef OSSL_STORE_LOADER_CTX *(*OSSL_STORE_open_fn)(const char *uri,

                                                      const UI_METHOD *ui_method,

                                                      void *ui_data);

 int OSSL_STORE_LOADER_set_open(OSSL_STORE_LOADER *store_loader,

                                OSSL_STORE_open_fn store_open_function);

 typedef int (*OSSL_STORE_ctrl_fn)(OSSL_STORE_LOADER_CTX *ctx, int cmd,

                                   va_list args);

 int OSSL_STORE_LOADER_set_ctrl(OSSL_STORE_LOADER *store_loader,

                                OSSL_STORE_ctrl_fn store_ctrl_function);

 typedef int (*OSSL_STORE_expect_fn)(OSSL_STORE_LOADER_CTX *ctx, int expected);

 int OSSL_STORE_LOADER_set_expect(OSSL_STORE_LOADER *loader,

                                  OSSL_STORE_expect_fn expect_function);

 typedef int (*OSSL_STORE_find_fn)(OSSL_STORE_LOADER_CTX *ctx,

                                   OSSL_STORE_SEARCH *criteria);

 int OSSL_STORE_LOADER_set_find(OSSL_STORE_LOADER *loader,

                                OSSL_STORE_find_fn find_function);

 typedef OSSL_STORE_INFO *(*OSSL_STORE_load_fn)(OSSL_STORE_LOADER_CTX *ctx,

                                                UI_METHOD *ui_method,

                                                void *ui_data);

 int OSSL_STORE_LOADER_set_load(OSSL_STORE_LOADER *store_loader,

                                OSSL_STORE_load_fn store_load_function);

 typedef int (*OSSL_STORE_eof_fn)(OSSL_STORE_LOADER_CTX *ctx);

 int OSSL_STORE_LOADER_set_eof(OSSL_STORE_LOADER *store_loader,

                               OSSL_STORE_eof_fn store_eof_function);

 typedef int (*OSSL_STORE_error_fn)(OSSL_STORE_LOADER_CTX *ctx);

 int OSSL_STORE_LOADER_set_error(OSSL_STORE_LOADER *store_loader,

                                 OSSL_STORE_error_fn store_error_function);

 typedef int (*OSSL_STORE_close_fn)(OSSL_STORE_LOADER_CTX *ctx);

 int OSSL_STORE_LOADER_set_close(OSSL_STORE_LOADER *store_loader,

                                 OSSL_STORE_close_fn store_close_function);

 void OSSL_STORE_LOADER_free(OSSL_STORE_LOADER *store_loader);

 int OSSL_STORE_register_loader(OSSL_STORE_LOADER *loader);

 OSSL_STORE_LOADER *OSSL_STORE_unregister_loader(const char *scheme);

=head1 DESCRIPTION

These functions help applications and engines to create loaders for

schemes they support.

=head2 Types

B<OSSL_STORE_LOADER> is the type to hold a loader.

It contains a scheme and the functions needed to implement

OSSL_STORE_open(), OSSL_STORE_load(), OSSL_STORE_eof(), OSSL_STORE_error() and

OSSL_STORE_close() for this scheme.

B<OSSL_STORE_LOADER_CTX> is a type template, to be defined by each loader

using B<struct ossl_store_loader_ctx_st { ... }>.

B<OSSL_STORE_open_fn>, B<OSSL_STORE_ctrl_fn>, B<OSSL_STORE_expect_fn>,

B<OSSL_STORE_find_fn>, B<OSSL_STORE_load_fn>, B<OSSL_STORE_eof_fn>,

and B<OSSL_STORE_close_fn>

are the function pointer types used within a STORE loader.

The functions pointed at define the functionality of the given loader.

=over 4

=item B<OSSL_STORE_open_fn>

This function takes a URI and is expected to interpret it in the best

manner possible according to the scheme the loader implements, it also

takes a B<UI_METHOD> and associated data, to be used any time

something needs to be prompted for.

Furthermore, this function is expected to initialize what needs to be

initialized, to create a private data store (B<OSSL_STORE_LOADER_CTX>, see

above), and to return it.

If something goes wrong, this function is expected to return NULL.

=item B<OSSL_STORE_ctrl_fn>

This function takes a B<OSSL_STORE_LOADER_CTX> pointer, a command number

B<cmd> and a B<va_list> B<args> and is used to manipulate loader

specific parameters.

=begin comment

Globally known command numbers are documented in L<OSSL_STORE_ctrl(3)>,

along with what B<args> are expected with each of them.

=end comment

Loader specific command numbers must begin at B<OSSL_STORE_C_CUSTOM_START>.

Any number below that is reserved for future globally known command

numbers.

This function is expected to return 1 on success, 0 on error.

=item B<OSSL_STORE_expect_fn>

This function takes a B<OSSL_STORE_LOADER_CTX> pointer and a B<OSSL_STORE_INFO>

identity B<expected>, and is used to tell the loader what object type is

expected.

B<expected> may be zero to signify that no specific object type is expected.

This function is expected to return 1 on success, 0 on error.

=item B<OSSL_STORE_find_fn>

This function takes a B<OSSL_STORE_LOADER_CTX> pointer and a

B<OSSL_STORE_SEARCH> search criterion, and is used to tell the loader what

to search for.

When called with the loader context being B<NULL>, this function is expected

to return 1 if the loader supports the criterion, otherwise 0.

When called with the loader context being something other than B<NULL>, this

function is expected to return 1 on success, 0 on error.

=item B<OSSL_STORE_load_fn>

This function takes a B<OSSL_STORE_LOADER_CTX> pointer and a B<UI_METHOD>

with associated data.

It's expected to load the next available data, mold it into a data

structure that can be wrapped in a B<OSSL_STORE_INFO> using one of the

L<OSSL_STORE_INFO(3)> functions.

If no more data is available or an error occurs, this function is

expected to return NULL.

The B<OSSL_STORE_eof_fn> and B<OSSL_STORE_error_fn> functions must indicate if

it was in fact the end of data or if an error occurred.

Note that this function retrieves I<one> data item only.

=item B<OSSL_STORE_eof_fn>

This function takes a B<OSSL_STORE_LOADER_CTX> pointer and is expected to

return 1 to indicate that the end of available data has been reached.

It is otherwise expected to return 0.

=item B<OSSL_STORE_error_fn>

This function takes a B<OSSL_STORE_LOADER_CTX> pointer and is expected to

return 1 to indicate that an error occurred in a previous call to the

B<OSSL_STORE_load_fn> function.

It is otherwise expected to return 0.

=item B<OSSL_STORE_close_fn>

This function takes a B<OSSL_STORE_LOADER_CTX> pointer and is expected to

close or shut down what needs to be closed, and finally free the

contents of the B<OSSL_STORE_LOADER_CTX> pointer.

It returns 1 on success and 0 on error.

=back

=head2 Functions

OSSL_STORE_LOADER_new() creates a new B<OSSL_STORE_LOADER>.

It takes an B<ENGINE> B<e> and a string B<scheme>.

B<scheme> must I<always> be set.

Both B<e> and B<scheme> are used as is and must therefore be alive as

long as the created loader is.

OSSL_STORE_LOADER_get0_engine() returns the engine of the B<store_loader>.

OSSL_STORE_LOADER_get0_scheme() returns the scheme of the B<store_loader>.

OSSL_STORE_LOADER_set_open() sets the opener function for the

B<store_loader>.

OSSL_STORE_LOADER_set_ctrl() sets the control function for the

B<store_loader>.

OSSL_STORE_LOADER_set_expect() sets the expect function for the

B<store_loader>.

OSSL_STORE_LOADER_set_load() sets the loader function for the

B<store_loader>.

OSSL_STORE_LOADER_set_eof() sets the end of file checker function for the

B<store_loader>.

OSSL_STORE_LOADER_set_close() sets the closing function for the

B<store_loader>.

OSSL_STORE_LOADER_free() frees the given B<store_loader>.

OSSL_STORE_register_loader() register the given B<store_loader> and thereby

makes it available for use with OSSL_STORE_open(), OSSL_STORE_load(),

OSSL_STORE_eof() and OSSL_STORE_close().

OSSL_STORE_unregister_loader() unregister the store loader for the given

B<scheme>.

=head1 NOTES

The B<file:> scheme has built in support.

=head1 RETURN VALUES

The functions with the types B<OSSL_STORE_open_fn>, B<OSSL_STORE_ctrl_fn>,

B<OSSL_STORE_expect_fn>,

B<OSSL_STORE_load_fn>, B<OSSL_STORE_eof_fn> and B<OSSL_STORE_close_fn> have the

same return values as OSSL_STORE_open(), OSSL_STORE_ctrl(), OSSL_STORE_expect(),

OSSL_STORE_load(), OSSL_STORE_eof() and OSSL_STORE_close(), respectively.

OSSL_STORE_LOADER_new() returns a pointer to a B<OSSL_STORE_LOADER> on success,

or B<NULL> on failure.

OSSL_STORE_LOADER_set_open(), OSSL_STORE_LOADER_set_ctrl(),

OSSL_STORE_LOADER_set_load(), OSSL_STORE_LOADER_set_eof() and

OSSL_STORE_LOADER_set_close() return 1 on success, or 0 on failure.

OSSL_STORE_register_loader() returns 1 on success, or 0 on failure.

OSSL_STORE_unregister_loader() returns the unregistered loader on success,

or B<NULL> on failure.

=head1 SEE ALSO

L<ossl_store(7)>, L<OSSL_STORE_open(3)>

=head1 HISTORY

OSSL_STORE_LOADER(), OSSL_STORE_LOADER_CTX(), OSSL_STORE_LOADER_new(),

OSSL_STORE_LOADER_set0_scheme(), OSSL_STORE_LOADER_set_open(),

OSSL_STORE_LOADER_set_ctrl(), OSSL_STORE_LOADER_set_load(),

OSSL_STORE_LOADER_set_eof(), OSSL_STORE_LOADER_set_close(),

OSSL_STORE_LOADER_free(), OSSL_STORE_register_loader(),

OSSL_STORE_unregister_loader(), OSSL_STORE_open_fn(), OSSL_STORE_ctrl_fn(),

OSSL_STORE_load_fn(), OSSL_STORE_eof_fn() and OSSL_STORE_close_fn()

were added in OpenSSL 1.1.1.

=head1 COPYRIGHT

Copyright 2016-2019 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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

L<https://www.openssl.org/source/license.html>.

=cut