LwEVT v0.1.0 documentation

Welcome to the documentation for version v0.1.0.

LwEVT is a simple event manager for embedded system. Its main purpose is to be able to send various events in the application from various modules. Application defines custom types with optional data structure to be sent to various application listeners.

_images/logo.svg

Download library Getting started Open Github Donate

Features

  • Written in ANSI C99

  • Platform independent, no architecture specific code

  • Flexible for application defined event types and associated data

  • Easy to use and maintain

  • User friendly MIT license

Requirements

  • C compiler

  • Few kB of non-volatile memory

Contribute

Fresh contributions are always welcome. Simple instructions to proceed:

  1. Fork Github repository

  2. Respect C style & coding rules used by the library

  3. Create a pull request to develop branch with new features or bug fixes

Alternatively you may:

  1. Report a bug

  2. Ask for a feature request

License

MIT License

Copyright (c) 2022 Tilen MAJERLE

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

Table of contents

Getting started

Getting started may be the most challenging part of every new library. This guide is describing how to start with the library quickly and effectively

Download library

Library is primarly hosted on Github.

You can get it by:

  • Downloading latest release from releases area on Github

  • Cloning main branch for latest stable version

  • Cloning develop branch for latest development

Download from releases

All releases are available on Github releases area.

Clone from Github
First-time clone

This is used when you do not have yet local copy on your machine.

  • Make sure git is installed.

  • Open console and navigate to path in the system to clone repository to. Use command cd your_path

  • Clone repository with one of available options below

    • Run git clone --recurse-submodules https://github.com/MaJerle/lwevt command to clone entire repository, including submodules

    • Run git clone --recurse-submodules --branch develop https://github.com/MaJerle/lwevt to clone development branch, including submodules

    • Run git clone --recurse-submodules --branch main https://github.com/MaJerle/lwevt to clone latest stable branch, including submodules

  • Navigate to examples directory and run favourite example

Update cloned to latest version

  • Open console and navigate to path in the system where your repository is located. Use command cd your_path

  • Run git pull origin main command to get latest changes on main branch

  • Run git pull origin develop command to get latest changes on develop branch

  • Run git submodule update --init --remote to update submodules to latest version

Note

This is preferred option to use when you want to evaluate library and run prepared examples. Repository consists of multiple submodules which can be automatically downloaded when cloning and pulling changes from root repository.

Add library to project

At this point it is assumed that you have successfully download library, either cloned it or from releases page. Next step is to add the library to the project, by means of source files to compiler inputs and header files in search path

  • Copy lwevt folder to your project, it contains library files

  • Add lwevt/src/include folder to include path of your toolchain. This is where C/C++ compiler can find the files during compilation process. Usually using -I flag

  • Add source files from lwevt/src/ folder to toolchain build. These files are built by C/C++ compiler

  • Copy lwevt/src/include/lwevt/lwevt_opts_template.h to project folder and rename it to lwevt_opts.h

  • Copy lwevt/src/include/lwevt/lwevt_types_template.h to project folder and rename it to lwevt_types.h

  • Build the project

Configuration file

Configuration file is used to overwrite default settings defined for the essential use case. Library comes with template config file, which can be modified according to needs. and it should be copied (or simply renamed in-place) and named lwevt_opts.h

Note

Default configuration template file location: lwevt/src/include/lwevt/lwevt_opts_template.h. File must be renamed to lwevt_opts.h first and then copied to the project directory where compiler include paths have access to it by using #include "lwevt_opts.h".

List of configuration options are available in the Configuration section. If any option is about to be modified, it should be done in configuration file

Template configuration file
 1/**
 2 * \file            lwevt_opts_template.h
 3 * \brief           LwEVT configuration file
 4 */
 5
 6/*
 7 * Copyright (c) 2022 Tilen MAJERLE
 8 *
 9 * Permission is hereby granted, free of charge, to any person
10 * obtaining a copy of this software and associated documentation
11 * files (the "Software"), to deal in the Software without restriction,
12 * including without limitation the rights to use, copy, modify, merge,
13 * publish, distribute, sublicense, and/or sell copies of the Software,
14 * and to permit persons to whom the Software is furnished to do so,
15 * subject to the following conditions:
16 *
17 * The above copyright notice and this permission notice shall be
18 * included in all copies or substantial portions of the Software.
19 *
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
22 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
23 * AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
24 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
25 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
26 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
27 * OTHER DEALINGS IN THE SOFTWARE.
28 *
29 * This file is part of LwEVT - Lightweight event manager.
30 *
31 * Author:          Tilen MAJERLE <tilen@majerle.eu>
32 * Version:         v0.1.0
33 */
34#ifndef LWEVT_HDR_OPTS_H
35#define LWEVT_HDR_OPTS_H
36
37/* Rename this file to "lwevt_opts.h" for your application */
38
39/*
40 * Open "include/lwevt/lwevt_opt.h" and
41 * copy & replace here settings you want to change values
42 */
43
44#endif /* LWEVT_HDR_OPTS_H */

Note

If you prefer to avoid using configuration file, application must define a global symbol LWEVT_IGNORE_USER_OPTS, visible across entire application. This can be achieved with -D compiler option.

Types file

Every project needs definition of various event types. lwevt_types.h file defines list of events and optional data structure next to the event type

Template types file
 1/**
 2 * \file            lwevt_types_template.h
 3 * \brief           LwEVT application types
 4 */
 5
 6/*
 7 * Copyright (c) 2022 Tilen MAJERLE
 8 *
 9 * Permission is hereby granted, free of charge, to any person
10 * obtaining a copy of this software and associated documentation
11 * files (the "Software"), to deal in the Software without restriction,
12 * including without limitation the rights to use, copy, modify, merge,
13 * publish, distribute, sublicense, and/or sell copies of the Software,
14 * and to permit persons to whom the Software is furnished to do so,
15 * subject to the following conditions:
16 *
17 * The above copyright notice and this permission notice shall be
18 * included in all copies or substantial portions of the Software.
19 *
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
22 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
23 * AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
24 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
25 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
26 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
27 * OTHER DEALINGS IN THE SOFTWARE.
28 *
29 * This file is part of LwEVT - Lightweight event manager.
30 *
31 * Author:          Tilen MAJERLE <tilen@majerle.eu>
32 * Version:         v0.1.0
33 */
34
35/* Rename this file to "lwevt_opts.h" for your application and do not use include guard macros */
36
37/*
38 * Define your different event types with 2 macros
39 *
40 * Basic definition - event type w/o possibility for data
41 * 
42 * LWEVT_TYPE_BASIC(APP_EVT_BASIC_1)
43 * 
44 * Extended definition - event type w/ possibility for data
45 * 
46 * LWEVT_TYPE_BASIC(APP_EVT_EXT_W_DATA_1, struct { uint32_t my_par1; uint32_t my_par2; } ext_w_data;)
47 */

User manual

LwEVT is simple event manager library, its sole purpose is to be able to isolate various application modules and communicate in-between through event manager library.

Idea behind the library is to allow every module to subscribe to events or publish them upon various events or actions.

Define application events

Note

At this point we assume you have properly setup the library from Getting started guideline.

Every application is different and wants to use different types of events and its related data to be part of it. It is important to define your own lwevt_types.h application file with your events.

There are 2 methods to define the event type:

In your lwevt_types.h declare list of your application defines, as per example below. This file has to be generated by user and is application specific.

Definition of event types
1/* Define basic types */
2LWEVT_TYPE_BASIC(LWEVT_TYPE_MY_BASIC_1)
3LWEVT_TYPE_BASIC(LWEVT_TYPE_MY_BASIC_2)
4LWEVT_TYPE_BASIC(LWEVT_TYPE_MY_BASIC_3)
5
6/* Define extended types */
7LWEVT_TYPE_EXT(LWEVT_TYPE_MY_EXT_1, struct { int par1; int par2; } ext1)
8LWEVT_TYPE_EXT(LWEVT_TYPE_MY_EXT_2, struct { int par3; int par4; } ext2)
9LWEVT_TYPE_EXT(LWEVT_TYPE_MY_EXT_3, struct { int par1; int par2; } ext3)

You are now ready to send events to all subscribed modules

Produce events

Producing (sending) the event is simple and requires to fill event type and potential data (only part of extended type).

Tip

Producer does not need to be subscribed to any events.

Produce event to all subscribers
 1#include "lwevt/lwevt.h"
 2
 3void
 4produce() {
 5    lwevt_t* evt;
 6
 7    /* Initialize event management system = must be called only once in the application */
 8    lwevt_init();
 9    
10    /*
11     * Get event handle, set event data and dispatch event
12     *
13     * Send basic event - without any data
14     */
15    evt = lwevt_get_handle();
16    lwevt_dispatch(LWEVT_TYPE_MY_BASIC_1);
17
18    /*
19     * Get event handle, set event data and dispatch event
20     *
21     * Send extended event - with data
22     */
23    evt = lwevt_get_handle();
24    evt->msg.ext1.par1 = 10;    /* Some value */
25    evt->msg.ext1.par2 = 12;    /* Some value */
26    lwevt_dispatch(LWEVT_TYPE_MY_EXT_1);
27    return 0;
28}

Subscribe to events

Subscribing to events involves calling lwevt_register() function with callback function as parameter. All events are processed in the callback function from now on.

Receive events from the application
 1#include "lwevt/lwevt.h"
 2
 3/* Define event functions */
 4static void
 5prv_evt_fn(lwevt_t* e) {
 6    printf("Event type: %u\r\n", (unsigned)e->type);
 7    switch (e->type) {
 8        case LWEVT_TYPE_MY_BASIC_1: {
 9            printf("Basic event type - no data\r\n");
10            break;
11        }
12        case LWEVT_TYPE_MY_EXT_1: {
13            printf("Extended event type - with data: par1: %d, par2: %d\r\n",
14                (int)e->msg.ext1.par1, (int)e->msg.ext1.par2);
15            break;
16        }
17        default:
18            break;
19    }
20}
21
22int
23main() {
24    lwevt_t* evt;
25
26    /* Initialize event management system = must be called only once in the application  */
27    lwevt_init();
28
29    /* Set 2 custom functions for event */
30    lwevt_register(prv_evt_fn);
31
32    /* Do nothing - events are handled in callback function */
33
34    return 0;
35}

Global and local event handle

To optimize memory consumption, main event handle is defined as static global variable in the LwEVT module. It is accessible through lwevt_get_handle() function and allows use of default lwevt_dispatch() function call to send event to the application.

Note

lwevt_get_handle() and lwevt_dispatch() are available only when LWEVT_CFG_ENABLE_DEFAULT_HANDLE is enabled

In multi-threading environment, application must ensure thread safety between get handle and dispatch calls. To avoid use of semaphore or mutexes, alternative is to always define local lwevt_t based variable and dispatch event using lwevt_dispatch_ex() function

Produce events with global or local event handle
 1#include "lwevt/lwevt.h"
 2
 3void
 4produce() {
 5    lwevt_t* evt_global;
 6    lwevt_t evt_local;
 7
 8    /*
 9     * Send event using global handle
10     * Thread safety has to be ensured in multi-threading environments
11     */
12    evt_global = lwevt_get_handle();
13    evt_global->msg.ext1.par1 = 10; /* Some value */
14    evt_global->msg.ext1.par2 = 12; /* Some value */
15    lwevt_dispatch(LWEVT_TYPE_MY_EXT_1);
16
17    /*
18     * Send event usin local handle
19     * No need to ensure thread safety
20     */
21    evt_local.msg.ext1.par1 = 10;   /* Some value */
22    evt_local.msg.ext1.par2 = 12;   /* Some value */
23    lwevt_dispatch(LWEVT_TYPE_MY_EXT_1);
24    return 0;
25}

API reference

List of all the modules:

LwEVT

group LWEVT

Lightweight event system.

Defines

LWEVT_TYPE_BASIC(name)

Defines basic event type with respective name, only.

Basic events do not have possibility to send data to application

#define LWEVT_TYPE_BASIC(MY_EVENT_NAME)

LWEVT_TYPE_EXT(name, data)

Defines extended event type with possibily to send data.

Data C-type has to be declared for proper use case

#define LWEVT_TYPE_EXT(MY_EVENT_NAME, struct {int par1; int par2;} my_event_name;)

Typedefs

typedef void (*lwevt_fn)(lwevt_t *evt)

Event callback function prototype.

Enums

enum lwevt_type_t

Event type.

Values:

enumerator LWEVT_TYPE_LAST

Last element on the list

Functions

void lwevt_init(void)

Initialize LwEVT module.

uint8_t lwevt_register(lwevt_fn evt_fn)

Register new event listener callback to event manager.

Parameters

evt_fn – Function to add to list of listeners

Returns

1 if added, 0 otherwise

lwevt_t *lwevt_get_handle(void)

Get default handle object for dispatch purpose.

Note

Available only when LWEVT_CFG_ENABLE_DEFAULT_HANDLE is enabled

Returns

Pointer to default event handle

uint8_t lwevt_dispatch(lwevt_type_t type)

Dispatch event to all registered functions.

Note

It uses default event handle as parameter

Note

Available only when LWEVT_CFG_ENABLE_DEFAULT_HANDLE is enabled

Parameters

type – [in] Event type to dispatch

Returns

1 if dispatched, 0 otherwise

uint8_t lwevt_dispatch_ex(lwevt_t *e, lwevt_type_t type)

Dispatch event to all registered functions using custom event handle object.

Parameters

  • e – Event handle used as parameter to listeners

  • type – Event type to dispatch

Returns

1 if dispatched, 0 otherwise

struct lwevt_t
#include <lwevt.h>

Main event structure.

Public Members

lwevt_type_t type

Event type

const unsigned int dummy

Dummy element if no others are used by user

union lwevt_t::[anonymous] msg

Message union for extended event types

Configuration

This is the default configuration of the middleware. When any of the settings shall be modified, it shall be done in dedicated application config lwevt_opts.h file.

Note

Check Getting started for guidelines on how to create and use configuration file.

group LWEVT_OPT

Default configuration setup.

Defines

LWEVT_CFG_MAX_EVT_LISTENERS

Maximum number of event listeners that can receive info on event dispatch.

It defines size of array for function pointers

LWEVT_CFG_ENABLE_DEFAULT_HANDLE

Enables 1 or disables 0 creation of default event handle.

When enabled, user can use lwevt_get_handle and lwevt_dispatch functions to operate on defualt handle.

When disabled, user must create event handle before every dispatch, and is only able to use lwevt_dispatch_ex function