UI_CREATE_METHOD(3SSL) OpenSSL UI_CREATE_METHOD(3SSL)
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 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>.
3.5.7 2026-06-09 UI_CREATE_METHOD(3SSL)
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