CでOO

main.c

#include <stdio.h>

#include "Object.c"
#include "String.c"

int main(void) {

	int len;
	struct String *s = new(String, "hello");
	len = s->length(s);
	printf("length : %d\n", len);

	s->set(s, "hello, world");
	len = s->length(s);
	printf("length : %d\n", len);

	s->set(s, "test")->puts(s)
		->set(s, "Hi!")->puts(s);


	s->destroy(s);

	return 0;
}

Object.c

#pragma once

#include <stdlib.h>
#include <stdarg.h>


typedef struct _Class * Class;
struct _Class {
	size_t size;
	void * (*new)(void *self, va_list *args);
};


//
// Class Object
//
typedef struct Object * _Object;
struct Object {
	void *self;
	Class super;

	void (*class)(_Object self);
};

void object_class(_Object self) {
	printf("Class : Object\n");
}
void* object_new(void *_self, va_list *args) {
	_Object self = _self;

	self->class = &object_class;

	return self;
}
static const struct _Class __Object = {
	sizeof(struct Object),
	&object_new
};
const void *Object = &__Object;



//
// Class Util
//
void* new(const void *_class, ...) {
	const struct _Class *obj = _class;

	va_list ap;
	va_start(ap, _class);
	void *p = calloc(1, obj->size);
	*(const struct _Class **)p = obj;
	p = (obj->new)(p, &ap);
	va_end(ap);

	return p;
}

String.c

#pragma once

#include <stdlib.h>
#include <string.h>
#include <stdarg.h>

#include "Object.c"

typedef struct String * _String;
struct String {
	void *self;
	_Object super;

	char *_str;
	int _length;

	void (*initialize)(_String self, va_list *args);
	void (*destroy)(_String self);
	_String (*set)(_String self, char *str);
	int (*length)(_String self);
	_String (*puts)(_String self);
};

void string_initialize(_String self, va_list *args) {
	char *text = va_arg(*args, char *);
	(self->set)(self, text);
}

void string_destroy(_String self) {
	free(self->_str);
	self->_str = 0;

	free(self);
}

_String string_set(_String self, char *str) {
	if (self == NULL) return NULL;

	free(self->_str);
	self->_str = malloc(strlen(str) + 1);
	strcpy(self->_str, str);

	self->_length = strlen(str);

	return self;
}

_String string_puts(_String self) {
	if (self == NULL) return NULL;

	printf("%s\n", self->_str);
	return self;
}

int string_length(_String self) {
	if (self == NULL) return 0;

	return self->_length;
}

void* string_new(void *_self, va_list *args) {
	_String self = _self;

	self->initialize = &string_initialize;
	self->destroy = &string_destroy;
	self->set = &string_set;
	self->length = &string_length;
	self->puts= &string_puts;

	(self->initialize)(self, args);

	return self;
}

static const struct _Class __String = {
	sizeof(struct String),
	&string_new
};
const void *String = &__String;