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UI_CREATE_METHOD(3)                 OpenSSL                UI_CREATE_METHOD(3)
NAME
       UI_METHOD, UI_create_method, UI_destroy_method, UI_method_set_opener,
       UI_method_set_writer, UI_method_set_flusher, UI_method_set_reader,
       UI_method_set_closer, UI_method_set_data_duplicator,
       UI_method_set_prompt_constructor, UI_method_set_ex_data,
       UI_method_get_opener, UI_method_get_writer, UI_method_get_flusher,
       UI_method_get_reader, UI_method_get_closer,
       UI_method_get_data_duplicator, UI_method_get_data_destructor,
       UI_method_get_prompt_constructor, UI_method_get_ex_data - user
       interface method creation and destruction
SYNOPSIS
        #include <openssl/ui.h>
        typedef struct ui_method_st UI_METHOD;
        UI_METHOD *UI_create_method(const char *name);
        void UI_destroy_method(UI_METHOD *ui_method);
        int UI_method_set_opener(UI_METHOD *method, int (*opener) (UI *ui));
        int UI_method_set_writer(UI_METHOD *method,
                                 int (*writer) (UI *ui, UI_STRING *uis));
        int UI_method_set_flusher(UI_METHOD *method, int (*flusher) (UI *ui));
        int UI_method_set_reader(UI_METHOD *method,
                                 int (*reader) (UI *ui, UI_STRING *uis));
        int UI_method_set_closer(UI_METHOD *method, int (*closer) (UI *ui));
        int UI_method_set_data_duplicator(UI_METHOD *method,
                                          void *(*duplicator) (UI *ui, void *ui_data),
                                          void (*destructor)(UI *ui, void *ui_data));
        int UI_method_set_prompt_constructor(UI_METHOD *method,
                                             char *(*prompt_constructor) (UI *ui,
                                                                          const char
                                                                          *object_desc,
                                                                          const char
                                                                          *object_name));
        int UI_method_set_ex_data(UI_METHOD *method, int idx, void *data);
        int (*UI_method_get_opener(const UI_METHOD *method)) (UI *);
        int (*UI_method_get_writer(const UI_METHOD *method)) (UI *, UI_STRING *);
        int (*UI_method_get_flusher(const UI_METHOD *method)) (UI *);
        int (*UI_method_get_reader(const UI_METHOD *method)) (UI *, UI_STRING *);
        int (*UI_method_get_closer(const UI_METHOD *method)) (UI *);
        char *(*UI_method_get_prompt_constructor(const UI_METHOD *method))
            (UI *, const char *, const char *);
        void *(*UI_method_get_data_duplicator(const UI_METHOD *method)) (UI *, void *);
        void (*UI_method_get_data_destructor(const UI_METHOD *method)) (UI *, void *);
        const void *UI_method_get_ex_data(const UI_METHOD *method, int idx);
DESCRIPTION
       A method contains a few functions that implement the low-level of the
       User Interface.  These functions are:
       an opener
           This function takes a reference to a UI and starts a session, for
           example by opening a channel to a tty, or by creating a dialog box.
       a writer
           This function takes a reference to a UI and a UI String, and writes
           the string where appropriate, maybe to the tty, maybe added as a
           field label in a dialog box.  Note that this gets fed all strings
           associated with a UI, one after the other, so care must be taken
           which ones it actually uses.
       a flusher
           This function takes a reference to a UI, and flushes everything
           that has been output so far.  For example, if the method builds up
           a dialog box, this can be used to actually display it and accepting
           input ended with a pressed button.
       a reader
           This function takes a reference to a UI and a UI string and reads
           off the given prompt, maybe from the tty, maybe from a field in a
           dialog box.  Note that this gets fed all strings associated with a
           UI, one after the other, so care must be taken which ones it
           actually uses.
       a closer
           This function takes a reference to a UI, and closes the session,
           maybe by closing the channel to the tty, maybe by destroying a
           dialog box.
       All of these functions are expected to return 0 on error, 1 on success,
       or -1 on out-off-band events, for example if some prompting has been
       cancelled (by pressing Ctrl-C, for example).  Only the flusher or the
       reader are expected to return -1.  If returned by another of the
       functions, it's treated as if 0 was returned.
       Regarding the writer and the reader, don't assume the former should
       only write and don't assume the latter should only read.  This depends
       on the needs of the method.
       For example, a typical tty reader wouldn't write the prompts in the
       write, but would rather do so in the reader, because of the sequential
       nature of prompting on a tty.  This is how the UI_OpenSSL() method does
       it.
       In contrast, a method that builds up a dialog box would add all prompt
       text in the writer, have all input read in the flusher and store the
       results in some temporary buffer, and finally have the reader just
       fetch those results.
       The central function that uses these method functions is UI_process(),
       and it does it in five steps:
       1.  Open the session using the opener function if that one's defined.
           If an error occurs, jump to 5.
       2.  For every UI String associated with the UI, call the writer
           function if that one's defined.  If an error occurs, jump to 5.
       3.  Flush everything using the flusher function if that one's defined.
           If an error occurs, jump to 5.
       4.  For every UI String associated with the UI, call the reader
           function if that one's defined.  If an error occurs, jump to 5.
       5.  Close the session using the closer function if that one's defined.
       UI_create_method() creates a new UI method with a given name.
       UI_destroy_method() destroys the given UI method ui_method.
       UI_method_set_opener(), UI_method_set_writer(),
       UI_method_set_flusher(), UI_method_set_reader() and
       UI_method_set_closer() set the five main method function to the given
       function pointer.
       UI_method_set_data_duplicator() sets the user data duplicator and
       destructor.  See UI_dup_user_data(3).
       UI_method_set_prompt_constructor() sets the prompt constructor.  See
       UI_construct_prompt(3).
       UI_method_set_ex_data() sets application specific data with a given
       EX_DATA index.  See CRYPTO_get_ex_new_index(3) for general information
       on how to get that index.
       UI_method_get_opener(), UI_method_get_writer(),
       UI_method_get_flusher(), UI_method_get_reader(),
       UI_method_get_closer(), UI_method_get_data_duplicator(),
       UI_method_get_data_destructor() and UI_method_get_prompt_constructor()
       return the different method functions.
       UI_method_get_ex_data() returns the application data previously stored
       with UI_method_set_ex_data().
RETURN VALUES
       UI_create_method() returns a UI_METHOD pointer on success, NULL on
       error.
       UI_method_set_opener(), UI_method_set_writer(),
       UI_method_set_flusher(), UI_method_set_reader(),
       UI_method_set_closer(), UI_method_set_data_duplicator() and
       UI_method_set_prompt_constructor() return 0 on success, -1 if the given
       method is NULL.
       UI_method_set_ex_data() returns 1 on success and 0 on error (because
       CRYPTO_set_ex_data() does so).
       UI_method_get_opener(), UI_method_get_writer(),
       UI_method_get_flusher(), UI_method_get_reader(),
       UI_method_get_closer(), UI_method_get_data_duplicator(),
       UI_method_get_data_destructor() and UI_method_get_prompt_constructor()
       return the requested function pointer if it's set in the method,
       otherwise NULL.
       UI_method_get_ex_data() returns a pointer to the application specific
       data associated with the method.
SEE ALSO
       UI(3), CRYPTO_get_ex_data(3), UI_STRING(3)
HISTORY
       The UI_method_set_data_duplicator(), UI_method_get_data_duplicator()
       and UI_method_get_data_destructor() functions were added in OpenSSL
       1.1.1.
COPYRIGHT
       Copyright 2001-2020 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>;.
1.1.1k                            2021-03-25               UI_CREATE_METHOD(3)