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

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);

DESCRIPTION

       These functions help applications and engines to create loaders for schemes they support.

   Types
       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.

       OSSL_STORE_LOADER_CTX is a type template, to be defined by each loader using struct
       ossl_store_loader_ctx_st { ... }.

       OSSL_STORE_open_fn, OSSL_STORE_ctrl_fn, OSSL_STORE_expect_fn, OSSL_STORE_find_fn,
       OSSL_STORE_load_fn, OSSL_STORE_eof_fn, and 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.

       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 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
           privata data store (OSSL_STORE_LOADER_CTX, see above), and to return it.  If something
           goes wrong, this function is expected to return NULL.

       OSSL_STORE_ctrl_fn
           This function takes a OSSL_STORE_LOADER_CTX pointer, a command number cmd and a
           va_list args and is used to manipulate loader specific parameters.

           Loader specific command numbers must begin at 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.

       OSSL_STORE_expect_fn
           This function takes a OSSL_STORE_LOADER_CTX pointer and a OSSL_STORE_INFO identity
           expected, and is used to tell the loader what object type is expected.  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.

       OSSL_STORE_find_fn
           This function takes a OSSL_STORE_LOADER_CTX pointer and a OSSL_STORE_SEARCH search
           criterion, and is used to tell the loader what to search for.

           When called with the loader context being 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 NULL, this function is
           expected to return 1 on success, 0 on error.

       OSSL_STORE_load_fn
           This function takes a OSSL_STORE_LOADER_CTX pointer and a 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 OSSL_STORE_INFO using one of the OSSL_STORE_INFO(3)
           functions.  If no more data is available or an error occurs, this function is expected
           to return NULL.  The OSSL_STORE_eof_fn and 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 one data item only.

       OSSL_STORE_eof_fn
           This function takes a 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.

       OSSL_STORE_error_fn
           This function takes a OSSL_STORE_LOADER_CTX pointer and is expected to return 1 to
           indicate that an error occurred in a previous call to the OSSL_STORE_load_fn function.
           It is otherwise expected to return 0.

       OSSL_STORE_close_fn
           This function takes a 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
           OSSL_STORE_LOADER_CTX pointer.  It returns 1 on success and 0 on error.

   Functions
       OSSL_STORE_LOADER_new() creates a new OSSL_STORE_LOADER.  It takes an ENGINE e and a
       string scheme.  scheme must always be set.  Both e and 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 store_loader.
       OSSL_STORE_LOADER_get0_scheme() returns the scheme of the store_loader.

       OSSL_STORE_LOADER_set_open() sets the opener function for the store_loader.

       OSSL_STORE_LOADER_set_ctrl() sets the control function for the store_loader.

       OSSL_STORE_LOADER_set_expect() sets the expect function for the store_loader.

       OSSL_STORE_LOADER_set_load() sets the loader function for the store_loader.

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

       OSSL_STORE_LOADER_set_close() sets the closing function for the store_loader.

       OSSL_STORE_LOADER_free() frees the given store_loader.

       OSSL_STORE_register_loader() register the given 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 scheme.

NOTES

       The file: scheme has built in support.

RETURN VALUES

       The functions with the types OSSL_STORE_open_fn, OSSL_STORE_ctrl_fn, OSSL_STORE_expect_fn,
       OSSL_STORE_load_fn, OSSL_STORE_eof_fn and 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 OSSL_STORE_LOADER on success, or 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 NULL on
       failure.

SEE ALSO

       ossl_store(7), OSSL_STORE_open(3)

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 to OpenSSL
       1.1.1.

COPYRIGHT

       Copyright 2016-2018 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 <https://www.openssl.org/source/license.html>.