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/*
* Copyright © 2022 Michael Smith <mikesmiffy128@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*/
#ifndef INC_EVENT_H
#define INC_EVENT_H
#define _EVENT_CAT4_(a, b, c, d) a##b##c##d
#define _EVENT_CAT4(a, b, c, d) _EVENT_CAT4_(a, b, c, d)
/*
* Declares an event defined somewhere in the codebase, allowing a handler to be
* defined with HANDLE_EVENT() below. Takes an optional list of types for
* parameters. The handler will be called every time the event is emitted by the
* declaring module.
*/
#define DECL_EVENT(evname, ...) typedef void _must_declare_event_##evname;
/*
* Declares a predicate - a special type of even returning bool. Predicates are
* used to determine whether some other action should be performed, and
* generally should not have side effects, since they get short-circuited and
* thus won't always fire when a check is being performed.
*/
#define DECL_PREDICATE(evname, ...) typedef bool _must_declare_event_##evname;
/*
* Defines an event belonging to this module. Doing so allows EMIT_<event>() to
* be called to fire handlers in all modules. Two modules (i.e. source files)
* cannot define an event (or predicate) with the same name.
*/
#define DEF_EVENT(event, ...) void EMIT_##event(__VA_ARGS__);
/*
* Defines a predicate belonging to this module. Doing so allows CHECK_<pred>()
* to be called to determine whether to perform some action. Predicates share a
* namespace with events and two modules cannot define two things with the same
* name.
*/
#define DEF_PREDICATE(pred, ...) bool CHECK_##pred(__VA_ARGS__);
/*
* Begins an event handler function that gets hooked up to an event by the code
* generation system. This is type-generic: if the event is a regular event,
* the function will return void; if it is a predicate it will return bool.
* Takes a function argument list which must match the type lists given to the
* above DEF/DECL macros.
*
* Note again that predicates are not guaranteed to fire at all due to
* short-circuiting and thus generally should not have side effects.
*
* In the current event implementation, each source file may handle only one of
* each event type, as any more wouldn't be too useful anyway.
*/
#define HANDLE_EVENT(evname, ...) \
_must_declare_event_##evname _EVENT_CAT4(_evhandler_, MODULE_NAME, _, \
evname)(__VA_ARGS__) /* function body here */
#endif
// vi: sw=4 ts=4 noet tw=80 cc=80
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