/*
 * bauble: a tiny room-based messaging system.
 *
 * zone.h: header information for zoned virtual memory
 *
 * virtual memory is implemented as a series of chunks, 64 bytes each,
 * with a header-block that's a bitmap of all the addressable virtual
 * memory (bits set represent used blocks.)  Used blocks have a 4-byte
 * header on them that gives the number of chunks that are allocated
 * in that block, plus a magic number for vfree() validation.  vmalloc
 * scans the bitmap to find enough contiguous chunks to give back, so
 * no other header information is needed.
 */
#ifndef _ZONE_H
#define _ZONE_H

#include <limits.h>	/* for CHAR_BITS definition */

#define	ZSIZE	64				/* memory chunksize */
#define	ZMAP	512				/* # words in zonemap */
#define	ZTOC	(ZMAP*sizeof(zonemap[0]))	/* # bytes in swapfile*/
#define	SZONES	(ZTOC*CHAR_BIT)			/* # zones in zonemap */
#define	SBITS	(CHAR_BIT*sizeof(zonemap[0]))	/* # bits per short */

extern unsigned short zonemap[ZMAP];	/* bitmap of allocated/free memory */

typedef struct {		/* zone header block */
    short z_magic;		/* magic number (0x42) */
    short z_segs;		/* # blocks occupied by used zone */
} zoneheader;

#define	Z_MAGIC	0x42		/* magic number for zone headers */

/* a couple of semi-handy macros */
#define	Zbit(x)    (1<<(x%SBITS))
#define	Zvalid(x)  ((x%ZSIZE) == sizeof(zoneheader))
#define	Zisfree(x) ((zonemap[x/SBITS] & Zbit(x)) == 0)
#define	Zfree(x)   (zonemap[x/SBITS] &= ~Zbit(x))
#define	Zalloc(x)  (zonemap[x/SBITS] |= Zbit(x))

extern int swapdev;				/* the vm swapfile */

#endif /*_ZONE_H*/