README.md

Żmija

Żmija is a simple universal code generation tool. It is intended to be used as a means to generate code that is both efficient and easily maintainable.

It is intended to be used in embedded systems with limited resources, however it can be used anywhere else as well.

Usage

Żmija lets you define sections in your code where code is generated automatically in accordance to a provided Python script. Such a section typically looks like this:

/* ~ZMIJA.GENERATOR:
def declare(variables):
	pass
	
def init(variables):
	pass
	
def generate(variables):
	return ""
*/// ~ZMIJA.GENERATED_CODE:

// ~ZMIJA.END

The section is defined inside a multi-line comment as to not affect the compilation of the code it is located in. Żmija supports any languge, including those that have non C-style comment styles (hence it is universal).

This is what the same section might look like inside a Lua script, for example:

--[[ ~ZMIJA.GENERATOR:
def declare(variables):
	pass
	
def init(variables):
	pass
	
def generate(variables):
	return ""
]]-- ~ZMIJA.GENERATED_CODE:

-- ~ZMIJA.END

Each section consists of a declare-function, an init-function and a generate-function. Each function is provided with the variables argument, which is a dictionary that is intended to be used for the storage of variables.

The declare-function is executed first. It is meant for variable declaration and should only reference its own variables.

The init-function is meant to initialize variables, including those of other sections. It is executed only after the declare-function has been executed for all sections in the project.

The generate-function returns the generated code for the section it is located in. It is executed only after the declare and init-functions of all sections have been executed.

Note: Empty functions can safely be removed.

Run python3 ./src/zmija.py /path/to/your/project/directory/ to perform the code generation. The generated code will be placed between the ~ZMIJA.GENERATED_CODE: and the ~ZMIJA.END lines.

Help output

Zmija. Simple universal code generation.

Usage:
	zmija.py path
	zmija.py path -d | --delete
	zmija.py path -c | --check-only
	zmija.py path --config-path="path/to/config"
	zmija.py -h | --help
	
Options:
	-h --help         Show this screen.
	-d --delete       Delete all generated code.
	-c --check-only   Check Python code for syntax and runtime errors without writing the
	                  changes to file.
	-u --unsafe       Skip the test pass. May cause data loss if the Python code raises
	                  exceptions, but offers better performance. Use with caution.
	--config-path     Provides a path to a configuration file.
	
Config:
	file_filter(file_path)     A function intended to filter file paths. Any file path
	                           for which this function returns False is ignored.

Config

You can define a file path filter function inside a config file, such that certain files are ignored by Żmija.

Here's what an example config file may look like:

def file_filter(file_path):
	return file_path.endswith('.cpp') or file_path.endswith('.h')

The file path of the config file needs to be supplied using the --config-file argument, like so:

python3 ./src/zmija.py /path/to/your/project/directory/ --config-file="/path/to/your/config/file"

Example

Say you have two modules, a ButtonController and a LedController. You would like to implement the observer pattern to allow the ButtonController to communicate with the LedController without depending on it.

The following C++ code implements this. It is a simple example where pressing the button toggles the LED.

#include <stdio.h>
#include <vector>
#include <functional>

// This would typically go into .h files:
struct ButtonController {
private:
    // Callbacks are functions that will be called
    // when the button is pressed. Notice how the
    // vector is constructed at runtime and held in
    // RAM.
    std::vector<std::function<void()>> callbacks;

public:
    void on_button_pressed();
    void register_callback(std::function<void()> cb);
};

struct LedController {
public:
    void toggle_led();

    LedController();
};



// This would typically go into .cpp files:
ButtonController *button_controller;
LedController *led_controller;

// This function is meant to be automatically
// called whenever a button is pressed.
void ButtonController::on_button_pressed() {
    // call all registered callbacks
    for (auto &cb : callbacks) cb();
}

// This function is meant to be called by other
// modules that would like to react to button
// presses.
void ButtonController::register_callback(std::function<void()> cb) {
    callbacks.push_back(cb);
}


void LedController::toggle_led() {
    printf("LED toggled.\n");
}

LedController::LedController() {
    // Registering a new callback consumes precious RAM.
    button_controller->register_callback([this]() {
        toggle_led();
    });
}

int main() {
    button_controller = new ButtonController();
    led_controller = new LedController();

    button_controller->on_button_pressed();

    return 0;
}

Calling the main() function will print LED toggled. to the console, as intended.

However, the ButtonController's callbacks vector is built during runtime and held in RAM. This causes an unnecessary overhead regarding both memory usage and execution speed.

Since the registered callbacks do not change after they have been registered, it may be beneficial to register them during compile time instead.

The following C++ code attempts to achieve this by using Żmija to generate the callbacks during compile time:

#include <stdio.h>

// This would typically go into .h files:
struct ButtonController {
public:
	void on_button_pressed();
};

struct LedController {
public:
	void toggle_led();

	LedController();
};



// This would typically go into .cpp files:
ButtonController *button_controller;
LedController *led_controller;

// This function is meant to be automatically
// called whenever a button is pressed.
void ButtonController::on_button_pressed() {
	/* ~ZMIJA.GENERATOR:
	def declare(variables):
		# Declare a new list called "on_button_pressed".
		# This list will contain calls to callback functions
		# in string form.
		variables["on_button_pressed"] = []
		
	def init(variables):
		# Nothing to do. This function can safely be removed.
		pass
		
	def generate(variables):
		# Return a string containing all callback calls,
		# separated by a newline character.
		return "\n".join(variables["on_button_pressed"])
	*/// ~ZMIJA.GENERATED_CODE:
	
	// ~ZMIJA.END
}


void LedController::toggle_led() {
	printf("LED toggled.\n");
}

LedController::LedController() {
	/* ~ZMIJA.GENERATOR:
	def declare(variables):
		# Nothing to do. This function can safely be removed.
		pass
	
	def init(variables):
		# Add a callback call in string form.
		# This string will be added to the ButtonController's 
		# generated code.
		variables["on_button_pressed"].append("led_controller->toggle_led();")
		
	def generate(variables):
		# Nothing to do. This function can safely be removed.
		return ''
	*/// ~ZMIJA.GENERATED_CODE:
	
	// ~ZMIJA.END
}

int main() {
	button_controller = new ButtonController();
	led_controller = new LedController();

	button_controller->on_button_pressed();

	return 0;
}

Let's run Żmija:

python3 ./src/zmija.py /path/to/your/project/directory/

This is what our newly generated .cpp file looks like now:

#include <stdio.h>

// This would typically go into .h files:
struct ButtonController {
public:
	void on_button_pressed();
};

struct LedController {
public:
	void toggle_led();

	LedController();
};



// This would typically go into .cpp files:
ButtonController *button_controller;
LedController *led_controller;

// This function is meant to be automatically
// called whenever a button is pressed.
void ButtonController::on_button_pressed() {
	/* ~ZMIJA.GENERATOR:
	def declare(variables):
		# Declare a new list called "on_button_pressed".
		# This list will contain calls to callback functions
		# in string form.
		variables["on_button_pressed"] = []
		
	def init(variables):
		# Nothing to do. This function can safely be removed.
		pass
		
	def generate(variables):
		# Return a string containing all callback calls,
		# separated by a newline character.
		return "\n".join(variables["on_button_pressed"])
	*/// ~ZMIJA.GENERATED_CODE:
	led_controller->toggle_led();
	// ~ZMIJA.END
}


void LedController::toggle_led() {
	printf("LED toggled.\n");
}

LedController::LedController() {
	/* ~ZMIJA.GENERATOR:
	def declare(variables):
		# Nothing to do. This function can safely be removed.
		pass
	
	def init(variables):
		# Add a callback call in string form.
		# This string will be added to the ButtonController's 
		# generated code.
		variables["on_button_pressed"].append("led_controller->toggle_led();")
		
	def generate(variables):
		# Nothing to do. This function can safely be removed.
		return ''
	*/// ~ZMIJA.GENERATED_CODE:
	
	// ~ZMIJA.END
}

int main() {
	button_controller = new ButtonController();
	led_controller = new LedController();

	button_controller->on_button_pressed();

	return 0;
}

As you can see, Żmija has generated the led_controller->toggle_led();-line, just as intended.