nps/Object.h

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#ifndef NPS_OBJECT_H
#define NPS_OBJECT_H

#include <stdarg.h>
#include <stdlib.h>
#include "../error/error.h"

/*
  There are two key struct types Objects and Classes.  Class inherits from Object.
*/

struct Object { 
    const struct Class *class;
    unsigned long count; /* reference count */    
};

struct Class {
  const struct Object descr; /* object struct is embedded within class == inheritance */
  const struct Class *super;
  size_t size;
  char *name;    
  /* methods follow */
  struct Object *(*ctor) (struct Object *, nps_error_t *, va_list *ap);    
  int (*dtor) (struct Object *, nps_error_t *error);    
};

/* Object (the type) is the root of all Objects. Class (the type) is the root of all classes.
   And yet... it is convenient to create _values_ with similar names that are classes (below).
   Class (the value) is the root of the class object hierarchy, whereas Object (the value) is 
   the class root of the non-Class Object hierarchy.  The descendents of Class (the value) 
   construct new Object classes in what is called a meta-class system. 
*/
extern const struct Class Object[];
extern const struct Class Class[];


/* The object system needs to be initialized before first use using
   nps_initObject();
*/
extern          void  nps_initObject();
/* Classes can be reclaimed at the end of the program using
   nps_releaseClasses */

extern           int  nps_releaseClasses(nps_error_t *error);

/* When used in conjunction with the CAST macro, cast provides a type safe
   casting mechanism. */
extern struct Object *nps_cast(const struct Class *to, struct Object *val);
/* retain() increments the reference count */
extern          void  nps_retain(  struct Object *o);     /* reference counting */
/* release() decrements the reference count */
extern           int  nps_release( struct Object *o, nps_error_t *err);
/* Construct an object of type class, using arguments givin in ..., and 
   setting the reference count to 1. */
extern struct Object *nps_new(const struct Class *class, nps_error_t *err,...);

#define CAST(cls,val) (struct cls *) nps_cast(cls,(struct Object *)val)
#define NEW(cls,nps_err,...)                                  \
    ((struct cls*) nps_new((struct Class *)cls, nps_err, __VA_ARGS__))

#define RELEASE(val,error) nps_release(CAST(Object,val),error)
#define RETAIN(val)   nps_retain(CAST(Object,val))

#endif

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