UI_CREATE_METHOD(3)

✨ UI_CREATE_METHOD 💅 — user interface method creation and destruction ✨

okay bestie, so this is a page from the Library Functions Manual about libcrypto and it's literally all about building your own UI methods. stay with me, it's giving very much "custom plug-in architecture" energy 👑

Also the whole girlie squad of functions we're covering here includes 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_prompt_constructor, UI_method_get_opener, UI_method_get_writer, UI_method_get_flusher, UI_method_get_reader, UI_method_get_closer and UI_method_get_prompt_constructor 🫶 like, yes, that's a lot of names, but they all do exactly what they say on the tin.

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🌸 SYNOPSIS 🌸

Link against libcrypto and pull in the header:

library "libcrypto"
#include <openssl/ui.h>

Then here's the whole roster of prototypes, verbatim, no cap:

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_prompt_constructor(UI_METHOD *method,
    char *(*prompt_constructor)(UI *ui, const char *object_desc, const char *object_name));

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(UI_METHOD *method))(UI *,
    const char *, const char *);

like yes the getter return types are feral to read, but they're just function pointers, i promise 🧚

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🦋 DESCRIPTION 🦋

So a method is basically a little bundle of functions that handles the low level of the User Interface. Think of it as the personality of your UI — the vibe check that decides how prompts actually get shown and how answers actually get read. 💖

Here's who's in the band:

🎀 an opener

Takes a reference to a UI and starts a session — like opening a channel to a tty, or popping up a dialog box. Main character energy: it kicks off the whole thing ✨

🎀 a writer

Takes a reference to a UI and a UI_STRING, and writes the string wherever appropriate — maybe to the tty, maybe as a field label in a dialog box. ⚠️ heads up: this gets fed all strings associated with a UI, one after the other, so you gotta be careful about which ones it actually uses.

🎀 a flusher

Takes a reference to a UI and flushes everything that's been output so far. Like, if your method builds up a dialog box, this is the moment you actually display it — and accept input, which ends when a button gets pressed. 💅

🎀 a reader

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. Same warning as the writer: it gets fed all strings associated with a UI, one after the other, so careful which ones it actually uses 🫶

🎀 a closer

Takes a reference to a UI and closes the session — maybe by closing the channel to the tty, maybe by destroying a dialog box. Cleanup queen 🌸

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So here's the contract: 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 😭). But listen: only the flusher or the reader are expected to return -1. If any of the other functions return it, it's treated as if 0 was returned. So don't go rogue. 💀

About the writer and the reader — do not assume the former should only write, and do not assume the latter should only read. It totally depends on what the method needs. fr fr.

For example: a typical tty reader wouldn't write the prompts in the writer — it'd rather do that in the reader, because prompting on a tty is sequential like that. That's exactly how the UI_OpenSSL(3) method does it. 👑

In contrast, a method that builds up a dialog box would add all the 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. Different strokes, same slay. 🌈

The central function that actually uses these method functions is UI_process(3), and it does the whole thing in five steps:

1. Open the session using the opener function — if that one is defined. If an error occurs, jump to 5.
2. For every UI String associated with the UI, call the writer function — if that one is defined. If an error occurs, jump to 5.
3. Flush everything using the flusher function — if that one is defined. If an error occurs, jump to 5.
4. For every UI String associated with the UI, call the reader function — if that one is defined. If an error occurs, jump to 5.
5. Close the session using the closer function — if that one is defined.

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💜 the actual functions

UI_create_method() creates a new UI method with a given name. Glow-up complete 💅

UI_destroy_method() destroys the given ui_method. rip bestie 🪦

UI_method_set_opener(), UI_method_set_writer(), UI_method_set_flusher(), UI_method_set_reader() and UI_method_set_closer() set one of the five main methods to the given function pointer. Pick your fighter 🎀

UI_method_set_prompt_constructor() sets the prompt constructor — see UI_construct_prompt(3) for the deets ✨

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⭐ RETURN VALUES ⭐

• UI_create_method() returns a UI_METHOD pointer on success or NULL on error 🥲
• UI_method_set_opener(), UI_method_set_writer(), UI_method_set_flusher(), UI_method_set_reader(), UI_method_set_closer(), and UI_method_set_prompt_constructor() return 0 on success or -1 if the given method is NULL. (empty method = sad method 😭)
• UI_method_get_opener(), UI_method_get_writer(), UI_method_get_flusher(), UI_method_get_reader(), UI_method_get_closer(), and UI_method_get_prompt_constructor() return the requested function pointer if it is set in the method, or otherwise NULL. no pointer, no problem 🌸

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🦋 SEE ALSO 🦋

• UI_get_string_type(3)
• UI_new(3)

go read those too, iykyk 📚

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👑 HISTORY 👑

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_get_opener(), UI_method_get_writer(), UI_method_get_flusher(), UI_method_get_reader(), and UI_method_get_closer() first appeared in OpenSSL 0.9.7 and have been available since OpenBSD 3.2. vintage but iconic 💅

UI_method_set_prompt_constructor() and UI_method_get_prompt_constructor() first appeared in OpenSSL 1.0.0 and have been available since OpenBSD 4.9. the newer additions to the family 🎀

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and that's the page, bestie! 💖 brought to you by the Debian crew, dated June 8, 2025 — and this was UI_CREATE_METHOD(3) from the Library Functions Manual. mwah 🫶✨