#include "consspaceobject.h"

#ifndef __conspage_h
#define __conspage_h

/**
 * the number of cons cells on a cons page. The maximum value this can
 * be (and consequently, the size which, by version 1, it will default
 * to) is the maximum value of an unsigned 32 bit integer, which is to
 * say 4294967296. However, we'll start small.
 */
#define CONSPAGESIZE 8

/**
 * the number of cons pages we will initially allow for. For
 * convenience we'll set up an array of cons pages this big; however,
 * later we will want a mechanism for this to be able to grow
 * dynamically to the maximum we can currently allow, which is
 * 4294967296.
 *
 * Note that this means the total number of addressable cons cells is
 * 1.8e19, each of 20 bytes; or 3e20 bytes in total; and there are 
 * up to a maximum of 4e9 of heap space objects, each of potentially
 * 4e9 bytes. So we're talking about a potential total of 8e100 bytes
 * of addressable memory, which is only slightly more than the
 * number of atoms in the universe.
 */
#define NCONSPAGES 8

/**
 * a cons page is essentially just an array of cons space objects. It
 * might later have a local free list (i.e. list of free cells on this
 * page) and a pointer to the next cons page, but my current view is
 * that that's probably unneccessary.
 */
struct cons_page {
    struct cons_space_object cell[CONSPAGESIZE];
};

/**
 * The (global) pointer to the (global) freelist. Not sure whether this ultimately 
 * belongs in this file.
 */
extern struct cons_pointer freelist;

/**
 * An array of pointers to cons pages.
 */
extern struct cons_page *conspages[NCONSPAGES];

/**
 * Frees the cell at the specified pointer. Dangerous, primitive, low
 * level.
 *
 * @pointer the cell to free
 */
void free_cell( struct cons_pointer pointer );

/**
 * Allocates a cell with the specified tag. Dangerous, primitive, low
 * level.
 *
 * @param tag the tag of the cell to allocate - must be a valid cons space tag.
 * @return the cons pointer which refers to the cell allocated.
 */
struct cons_pointer allocate_cell( char *tag );

/**
 * initialise the cons page system; to be called exactly once during startup.
 */
void initialise_cons_pages(  );

/**
 * dump the allocated pages to this output stream.
 */
void dump_pages( FILE * output );

#endif