quakeforge/libs/util/zone.c

/*
	zone.c

	(description)

	Copyright (C) 1996-1997  Id Software, Inc.

	This program is free software; you can redistribute it and/or
	modify it under the terms of the GNU General Public License
	as published by the Free Software Foundation; either version 2
	of the License, or (at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

	See the GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to:

		Free Software Foundation, Inc.
		59 Temple Place - Suite 330
		Boston, MA  02111-1307, USA

*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

static __attribute__ ((used)) const char rcsid[] = 
	"$Id$";

#ifdef HAVE_STRING_H
# include <string.h>
#endif
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif

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

#include "QF/cmd.h"
#include "QF/cvar.h"
#include "QF/qargs.h"
#include "QF/sys.h"
#include "QF/zone.h"

#include "compat.h"

static void Cache_FreeLow (int new_low_hunk);
static void Cache_Profile (void);
static qboolean Cache_FreeLRU (void);

#define	ZONEID			0x1d4a11
#define	HUNK_SENTINAL	0x1df001ed

#define MINFRAGMENT	64

/*
   						ZONE MEMORY ALLOCATION

	There is never any space between memblocks, and there will never be two
	contiguous free memblocks.

	The rover can be left pointing at a non-empty block

	The zone calls are pretty much used only for small strings and structures,
	all big things are allocated on the hunk.
*/

typedef struct memblock_s
{
	int         size;		// including the header and possibly tiny fragments
	int         tag;		// a tag of 0 is a free block
	struct memblock_s *next, *prev;
	int         id;			// should be ZONEID
	int         id2;		// pad to 64 bit boundary
} memblock_t;

struct memzone_s
{
	int         size;		// total bytes malloced, including header
	int         used;		// ammount used, including header
	int         offset;
	int         ele_size;
	memblock_t  blocklist;	// start / end cap for linked list
	memblock_t  *rover;
};


static int
z_block_size (memblock_t *block)
{
	return block->size - sizeof (memblock_t) - 4;
}

static int
z_offset (memzone_t *zone, memblock_t *block)
{
	int         offset = ((byte *) (block + 1) - (byte *) zone);
	
	return offset / zone->ele_size + zone->offset;
}

VISIBLE void
Z_ClearZone (memzone_t *zone, int size, int zone_offset, int ele_size)
{
	memblock_t	*block;
	
	// set the entire zone to one free block

	block = (memblock_t *) (zone + 1);
	zone->blocklist.next = block;
	zone->blocklist.prev = block;
	zone->blocklist.tag = 1;	// in use block
	zone->blocklist.id = 0;
	zone->blocklist.size = 0;
	zone->offset = zone_offset;
	zone->ele_size = ele_size;
	zone->rover = block;
	zone->size = size;
	zone->used = sizeof (memzone_t);
	
	block->prev = block->next = &zone->blocklist;
	block->tag = 0;			// free block
	block->id = ZONEID;
	block->id2 = ZONEID;
	block->size = size - sizeof (memzone_t);
}

VISIBLE void
Z_Free (memzone_t *zone, void *ptr)
{
	memblock_t	*block, *other;

	if (!ptr)
		Sys_Error ("Z_Free: NULL pointer");

	block = (memblock_t *) ((byte *) ptr - sizeof (memblock_t));
	if (((byte *) block < (byte *) zone)
		|| (((byte *) block) >= (byte *) zone + zone->size))
		Sys_Error ("Z_Free: freed a pointer outside of the zone: %x",
				   z_offset (zone, block));
	if (block->id != ZONEID || block->id2 != ZONEID) {
		Sys_Printf ("bad pointer %x\n", z_offset (zone, block));
		Z_Print (zone);
		fflush (stdout);
		Sys_Error ("Z_Free: freed a pointer without ZONEID");
	}
	if (block->tag == 0)
		Sys_Error ("Z_Free: freed a freed pointer");

	block->tag = 0;		// mark as free
	zone->used -= block->size;
	
	other = block->prev;
	if (!other->tag) {
		// merge with previous free block
		other->size += block->size;
		other->next = block->next;
		other->next->prev = other;
		if (block == zone->rover)
			zone->rover = other;
		block = other;
	}
	
	other = block->next;
	if (!other->tag) {
		// merge the next free block onto the end
		block->size += other->size;
		block->next = other->next;
		block->next->prev = block;
		if (other == zone->rover)
			zone->rover = block;
	}
}

VISIBLE void *
Z_Malloc (memzone_t *zone, int size)
{
	void	*buf;

	if (!developer || developer->int_val & SYS_DEV)
		Z_CheckHeap (zone);	// DEBUG
	buf = Z_TagMalloc (zone, size, 1);
	if (!buf)
		Sys_Error ("Z_Malloc: failed on allocation of %i bytes",size);
	memset (buf, 0, size);

	return buf;
}

void *
Z_TagMalloc (memzone_t *zone, int size, int tag)
{
	int			 extra;
	memblock_t	*start, *rover, *new, *base;

	if (!tag)
		Sys_Error ("Z_TagMalloc: tried to use a 0 tag");

	// scan through the block list looking for the first free block
	// of sufficient size
	size += sizeof (memblock_t);	// account for size of block header
	size += 4;						// space for memory trash tester
	size = (size + 7) & ~7;			// align to 8-byte boundary
	
	base = rover = zone->rover;
	start = base->prev;
	
	do {
		if (rover == start)			// scaned all the way around the list
			return NULL;
		if (rover->tag)
			base = rover = rover->next;
		else
			rover = rover->next;
	} while (base->tag || base->size < size);
	
	// found a block big enough
	extra = base->size - size;
	if (extra >  MINFRAGMENT) {
		// there will be a free fragment after the allocated block
		new = (memblock_t *) ((byte *) base + size);
		new->size = extra;
		new->tag = 0;			// free block
		new->prev = base;
		new->id = ZONEID;
		new->id2 = ZONEID;
		new->next = base->next;
		new->next->prev = new;
		base->next = new;
		base->size = size;
	}
	
	base->tag = tag;				// no longer a free block
	
	zone->rover = base->next;	// next allocation will start looking here
	
	base->id = ZONEID;
	base->id2 = ZONEID;

	zone->used += base->size;

	// marker for memory trash testing
	*(int *) ((byte *) base + base->size - 4) = ZONEID;

	return (void *) (base + 1);
}

VISIBLE void *
Z_Realloc (memzone_t *zone, void *ptr, int size)
{
	int         old_size;
	memblock_t *block;
	void       *old_ptr;
	
	if (!ptr)
		return Z_Malloc (zone, size);

	block = (memblock_t *) ((byte *) ptr - sizeof (memblock_t));
	if (block->id != ZONEID || block->id2 != ZONEID)
		Sys_Error ("Z_Realloc: realloced a pointer without ZONEID");
	if (block->tag == 0)
		Sys_Error ("Z_Realloc: realloced a freed pointer");

	old_size = block->size;
	old_size -= sizeof (memblock_t);	// account for size of block header
	old_size -= 4;						// space for memory trash tester
	old_ptr = ptr;

	Z_Free (zone, ptr);
	ptr = Z_TagMalloc (zone, size, 1);
	if (!ptr)
		Sys_Error ("Z_Realloc: failed on allocation of %i bytes", size);

	if (ptr != old_ptr)
		memmove (ptr, old_ptr, min (old_size, size));

	return ptr;
}

void
Z_Print (memzone_t *zone)
{
	memblock_t	*block;

	Sys_Printf ("zone size: %i  location: %p  used: %i\n",
				zone->size, zone, zone->used);

	for (block = zone->blocklist.next ; ; block = block->next) {
		Sys_Printf ("block:%p    size:%7i    tag:%3i ofs:%x\n",
					block, z_block_size (block),
					block->tag, z_offset (zone, block));

		if (block->next == &zone->blocklist)
			break;			// all blocks have been hit	
		if (block->id != ZONEID || block->id2 != ZONEID)
			Sys_Printf ("ERROR: block ids incorrect\n");
		if ( (byte *)block + block->size != (byte *)block->next)
			Sys_Printf ("ERROR: block size does not touch the next block\n");
		if ( block->next->prev != block)
			Sys_Printf ("ERROR: next block doesn't have proper back link\n");
		if (!block->tag && !block->next->tag)
			Sys_Printf ("ERROR: two consecutive free blocks\n");
		if (block->tag
			&& (*(int *) ((byte *) block + block->size - 4) != ZONEID))
			Sys_Printf ("ERROR: memory trashed in block\n");
		fflush (stdout);
	}
}

void
Z_CheckHeap (memzone_t *zone)
{
	memblock_t	*block;

	for (block = zone->blocklist.next ; ; block = block->next) {
		if (block->next == &zone->blocklist)
			break;			// all blocks have been hit	
		if ( (byte *)block + block->size != (byte *)block->next)
			Sys_Error ("Z_CheckHeap: block size does not touch the next "
					   "block\n");
		if ( block->next->prev != block)
			Sys_Error ("Z_CheckHeap: next block doesn't have proper back "
					   "link\n");
		if (!block->tag && !block->next->tag)
			Sys_Error ("Z_CheckHeap: two consecutive free blocks\n");
	}
}

//============================================================================

typedef struct {
	int         sentinal;
	int         size;			// including sizeof(hunk_t), -1 = not allocated
	char        name[8];
} hunk_t;

byte       *hunk_base;
int         hunk_size;
int         hunk_low_used;
int         hunk_high_used;
int         hunk_tempmark;

qboolean    hunk_tempactive;

/*
	Hunk_Check

	Run consistancy and sentinal trahing checks
*/
VISIBLE void
Hunk_Check (void)
{
	hunk_t     *h;

	for (h = (hunk_t *) hunk_base; (byte *) h != hunk_base + hunk_low_used;) {
		if (h->sentinal != HUNK_SENTINAL)
			Sys_Error ("Hunk_Check: trashed sentinal");
		if (h->size < 16 || h->size + (byte *) h - hunk_base > hunk_size)
			Sys_Error ("Hunk_Check: bad size");
		h = (hunk_t *) ((byte *) h + h->size);
	}
}

/*
	Hunk_Print

	If "all" is specified, every single allocation is printed.
	Otherwise, allocations with the same name will be totaled up before
	printing.
*/
/*
static void
Hunk_Print (qboolean all)
{
	char        name[9];
	hunk_t     *h, *next, *endlow, *starthigh, *endhigh;
	int         count, sum, totalblocks;

	name[8] = 0;
	count = 0;
	sum = 0;
	totalblocks = 0;

	h = (hunk_t *) hunk_base;
	endlow = (hunk_t *) (hunk_base + hunk_low_used);
	starthigh = (hunk_t *) (hunk_base + hunk_size - hunk_high_used);
	endhigh = (hunk_t *) (hunk_base + hunk_size);

	Sys_Printf ("          :%8i total hunk size\n", hunk_size);
	Sys_Printf ("-------------------------\n");

	while (1) {
		// skip to the high hunk if done with low hunk
		if (h == endlow) {
			Sys_Printf ("-------------------------\n");
			Sys_Printf ("          :%8i REMAINING\n",
						hunk_size - hunk_low_used - hunk_high_used);
			Sys_Printf ("-------------------------\n");
			h = starthigh;
		}
		// if totally done, break
		if (h == endhigh)
			break;

		// run consistancy checks
		if (h->sentinal != HUNK_SENTINAL)
			Sys_Error ("Hunk_Check: trahsed sentinal");
		if (h->size < 16 || h->size + (byte *) h - hunk_base > hunk_size)
			Sys_Error ("Hunk_Check: bad size");

		next = (hunk_t *) ((byte *) h + h->size);
		count++;
		totalblocks++;
		sum += h->size;

		// print the single block
		memcpy (name, h->name, 8);
		if (all)
			Sys_Printf ("%8p :%8i %8s\n", h, h->size, name);

		// print the total
		if (next == endlow || next == endhigh ||
			strncmp (h->name, next->name, 8)) {
			if (!all)
				Sys_Printf ("          :%8i %8s (TOTAL)\n", sum, name);
			count = 0;
			sum = 0;
		}

		h = next;
	}

	Sys_Printf ("-------------------------\n");
	Sys_Printf ("%8i total blocks\n", totalblocks);
}
*/
static void
Hunk_FreeToHighMark (int mark)
{
	if (hunk_tempactive) {
		hunk_tempactive = false;
		Hunk_FreeToHighMark (hunk_tempmark);
	}
	if (mark < 0 || mark > hunk_high_used)
		Sys_Error ("Hunk_FreeToHighMark: bad mark %i", mark);
	memset (hunk_base + hunk_size - hunk_high_used, 0, hunk_high_used - mark);
	hunk_high_used = mark;
}

static int
Hunk_HighMark (void)
{
	if (hunk_tempactive) {
		hunk_tempactive = false;
		Hunk_FreeToHighMark (hunk_tempmark);
	}

	return hunk_high_used;
}

VISIBLE void *
Hunk_AllocName (int size, const char *name)
{
	hunk_t     *h;

#ifdef PARANOID
	Hunk_Check ();
#endif

	if (size < 0)
		Sys_Error ("Hunk_Alloc: bad size: %i", size);

	size = sizeof (hunk_t) + ((size + 15) & ~15);

	if (hunk_size - hunk_low_used - hunk_high_used < size) {
		Hunk_HighMark();
		Cache_FreeLRU ();
	}
	if (hunk_size - hunk_low_used - hunk_high_used < size) {
		int         mem = hunk_size / (1024 * 1024);
		mem += 8;
		mem &= ~7;
		Cache_Profile ();
		Sys_Error
			("Not enough RAM allocated.  Try starting using \"-mem %d\" on "
			 "the %s command line. (%d -  %d - %d < %d)", mem,
			 PACKAGE_NAME, hunk_size, hunk_low_used, hunk_high_used, size);
	}

	h = (hunk_t *) (hunk_base + hunk_low_used);
	hunk_low_used += size;

	Cache_FreeLow (hunk_low_used);

	memset (h, 0, size);

	h->size = size;
	h->sentinal = HUNK_SENTINAL;
	strncpy (h->name, name, 8);

	return (void *) (h + 1);
}

VISIBLE void *
Hunk_Alloc (int size)
{
	return Hunk_AllocName (size, "unknown");
}

VISIBLE int
Hunk_LowMark (void)
{
	return hunk_low_used;
}

VISIBLE void
Hunk_FreeToLowMark (int mark)
{
	if (mark < 0 || mark > hunk_low_used)
		Sys_Error ("Hunk_FreeToLowMark: bad mark %i", mark);
	memset (hunk_base + mark, 0, hunk_low_used - mark);
	hunk_low_used = mark;
}

static void *
Hunk_HighAlloc (int size)
{
	if (size < 0)
		Sys_Error ("Hunk_HighAlloc: bad size: %i", size);

	if (hunk_tempactive) {
		Hunk_FreeToHighMark (hunk_tempmark);
		hunk_tempactive = false;
	}
#ifdef PARANOID
	Hunk_Check ();
#endif

	size = ((size + 15) & ~15);

	if (hunk_size - hunk_low_used - hunk_high_used < size) {
		Sys_Printf ("Hunk_HighAlloc: failed on %i bytes\n", size);
		return NULL;
	}

	hunk_high_used += size;

	return (void *) (hunk_base + hunk_size - hunk_high_used);
}

/*
	Hunk_TempAlloc

	Return space from the top of the hunk
*/
VISIBLE void *
Hunk_TempAlloc (int size)
{
	void       *buf;

	size = (size + 15) & ~15;

	if (hunk_tempactive) {
		if (hunk_high_used - hunk_tempmark >= size + (int) sizeof (hunk_t)) {
			return (hunk_t *) (hunk_base + hunk_size - hunk_high_used) + 1;
		}
		Hunk_FreeToHighMark (hunk_tempmark);
		hunk_tempactive = false;
	}

	hunk_tempmark = Hunk_HighMark ();

	buf = Hunk_HighAlloc (size);

	hunk_tempactive = true;

	return buf;
}

/* CACHE MEMORY */

typedef struct cache_system_s cache_system_t;
struct cache_system_s {
	cache_system_t *prev, *next;
	cache_system_t *lru_prev, *lru_next;	// for LRU flushing 
	char        name[16];
	size_t      size;							// including this header
	int			readlock;
	cache_user_t *user;
};

static cache_system_t cache_head;

static cache_system_t *Cache_TryAlloc (size_t size, qboolean nobottom);
#if 0
static void
check_cache (void)
{
	cache_system_t *cs;
	int used = hunk_tempactive ? hunk_tempmark : hunk_high_used;

	for (cs = cache_head.prev; cs != &cache_head; cs = cs->prev)
		if (cs->prev != &cache_head) {
			if ((byte *) cs + cs->size != (byte *) cs->prev)
				Sys_Error ("inconsistent cache %p %p %d %d", cs, cs->prev,
						   (int)cs->size,
						   (int) ((char *)cs->prev - (char *)cs));
			if (hunk_size - ((byte*)cs - hunk_base) > used)
				Sys_Error ("cache block out of high hunk");
		}
	if (cache_head.prev != &cache_head &&
		hunk_size - ((byte*) cache_head.prev - hunk_base) != used)
		Sys_Error ("cache bottom not at bottom of high hunk");
}
#endif
static void
Cache_Move (cache_system_t * c)
{
	cache_system_t *new;

	// we are clearing up space at the bottom, so allocate it late
	new = Cache_TryAlloc (c->size, true);
	if (new) {
		Sys_MaskPrintf (SYS_DEV, "cache_move ok\n");

		memcpy (new + 1, c + 1, c->size - sizeof (cache_system_t));
		new->user = c->user;
		memcpy (new->name, c->name, sizeof (new->name));
		Cache_Free (c->user);
		new->user->data = (void *) (new + 1);
	} else {
		Sys_MaskPrintf (SYS_DEV, "cache_move failed\n");

		Cache_Free (c->user);			// tough luck...
	}
}

/*
	Cache_FreeLow

	Throw things out until the hunk can be expanded to the given point
*/
static void
Cache_FreeLow (int new_low_hunk)
{
	cache_system_t *c;

	while (1) {
		c = cache_head.prev;
		if (c == &cache_head)
			return;						// nothing in cache at all
		if ((byte *) c >= hunk_base + new_low_hunk)
			return;						// there is space to grow the hunk
		Sys_Error ("FIXME: Cache_FreeLow: not enough memory");
		Cache_Move (c);					// reclaim the space
	}
}

static inline void
Cache_UnlinkLRU (cache_system_t * cs)
{
	if (!cs->lru_next || !cs->lru_prev)
		Sys_Error ("Cache_UnlinkLRU: NULL link: %s %p %p",
				   cs->name, cs->lru_next, cs->lru_prev);

	cs->lru_next->lru_prev = cs->lru_prev;
	cs->lru_prev->lru_next = cs->lru_next;

	cs->lru_prev = cs->lru_next = NULL;
}

static void
Cache_MakeLRU (cache_system_t * cs)
{
	if (cs->lru_next || cs->lru_prev)
		Sys_Error ("Cache_MakeLRU: active link: %s %p %p",
				   cs->name, cs->lru_next, cs->lru_prev);

	cache_head.lru_next->lru_prev = cs;
	cs->lru_next = cache_head.lru_next;
	cs->lru_prev = &cache_head;
	cache_head.lru_next = cs;
}

static qboolean
Cache_FreeLRU (void)
{
	cache_system_t *cs;

	//check_cache ();
	for (cs = cache_head.lru_prev;
		 cs != &cache_head && cs->readlock; cs = cs->lru_prev)
		;
	if (cs == &cache_head)
		return 0;
	Cache_Free (cs->user);
	return 1;
}

static void
link_cache_system (cache_system_t *new, cache_system_t *cs)
{
	new->next = cs;
	new->prev = cs->prev;
	cs->prev->next = new;
	cs->prev = new;

}

/*
	Cache_TryAlloc

	Looks for a free block of memory between the high and low hunk marks
	Size should already include the header and padding
*/
static cache_system_t *
Cache_TryAlloc (size_t size, qboolean nobottom)
{
	cache_system_t *cs, *new;

	//check_cache ();
	// is the cache completely empty?
	if (!nobottom && cache_head.prev == &cache_head) {
		new = (cache_system_t *) Hunk_HighAlloc (size);
		if (!new)
			return 0;
		memset (new, 0, size);
		new->size = size;
		cache_head.prev = cache_head.next = new;
		new->prev = new->next = &cache_head;
		Cache_MakeLRU (new);
		//check_cache ();
		return new;
	}

	// search for space in existing cache
	for (cs = cache_head.next; cs != &cache_head; cs = cs->next) {
		if (cs->user)
			continue;					// block isn't free
		if (cs->size >= size) {
			// found a big enough free block. If possible, carve it up for
			// later reuse, using the upper portion of the block for the
			// newly allocated block.
			new = cs;
			if (size - cs->size >= sizeof (cache_system_t)) {
				new = (cache_system_t *) ((char *) cs + cs->size - size);
				memset (new, 0, size);
				new->size = size;
				cs->size -= size;
				link_cache_system (new, cs);
				//check_cache ();
			}
			Cache_MakeLRU (new);
			return new;
		}
	}

	if (nobottom)
		return 0;

	// didn't find a free block, so make a new one.
	new = Hunk_HighAlloc (size);
	if (new) {
		memset (new, 0, size);
		new->size = size;
		link_cache_system (new, &cache_head);
		Cache_MakeLRU (new);
		//check_cache ();
		return new;
	}

	return 0;							// couldn't allocate
}

static void
Cache_Profile (void)
{
	cache_system_t *cs;
	unsigned int i;
	unsigned int items[31] = {0}, sizes[31] = {0};
	int count = 0, total = 0;

	cs = cache_head.next;
	while (cs != &cache_head) {
		for (i = 0; (cs->size >> (i + 1)) && i < 30; i++)
			;
		items[i]++;
		sizes[i] += cs->size;
		total += cs->size;
		count++;
		cs = cs->next;
	}
	Sys_Printf ("Cache Profile:\n");
	Sys_Printf ("%8s  %8s  %8s  %8s  %8s\n",
				"count", "min", "max", "average", "percent");
	for (i = 0; i < 31; i++) {
		if (!items[i])
			continue;
		Sys_Printf ("%8d  %8d  %8d  %8d  %7d%%\n",
					items[i], 1 << i, (1 << (i + 1)) - 1,
					sizes[i] / items[i],
					(sizes[i] * 100) / total);
	}
	Sys_Printf ("Total allocations: %d in %d allocations, average of"
				" %d per allocation\n", total, count, total / count);
}

static void
Cache_Print (void)
{
	cache_system_t *cd;

	for (cd = cache_head.next; cd != &cache_head; cd = cd->next) {
		Sys_Printf ("%8d : %s\n", (int) cd->size, cd->name);
	}
}

static void
Cache_Init (void)
{
	cache_head.next = cache_head.prev = &cache_head;
	cache_head.lru_next = cache_head.lru_prev = &cache_head;
	cache_head.user = (cache_user_t *) 1;	// make it look allocated
	cache_head.readlock = 1; // don't try to free or move it

	Cmd_AddCommand ("cache_flush", Cache_Flush, "Clears the current game "
					"cache");
	Cmd_AddCommand ("cache_profile", Cache_Profile, "Prints a profile of "
					"the current cache");
	Cmd_AddCommand ("cache_print", Cache_Print, "Prints out items in the "
					"cache");
}

/*
	Cache_Flush

	Throw everything out, so new data will be demand cached
*/
void
Cache_Flush (void)
{
	// cache_head.prev is guaranteed to not be free because it's the bottom
	// one and Cache_Free actually properly releases it
	while (cache_head.prev != &cache_head) {
		if (!cache_head.prev->user->data)
			Sys_Error ("Cache_Flush: user/system out of sync for "
					   "'%s' with %d size",
					   cache_head.prev->name, (int) cache_head.prev->size);
		Cache_Free (cache_head.prev->user);	// reclaim the space
	}
}

VISIBLE void *
Cache_Check (cache_user_t *c)
{
	cache_system_t *cs;

	if (!c->data)
		return NULL;

	cs = ((cache_system_t *) c->data) - 1;

	// move to head of LRU
	Cache_UnlinkLRU (cs);
	Cache_MakeLRU (cs);

	return c->data;
}

/*
	Cache_Free

	Frees the memory and removes it from the LRU list
*/
VISIBLE void
Cache_Free (cache_user_t *c)
{
	cache_system_t *cs;

	if (!c->data)
		Sys_Error ("Cache_Free: not allocated");

	cs = ((cache_system_t *) c->data) - 1;

	if (cs->readlock)
		Sys_Error ("Cache_Free: attempt to free locked block");

	Sys_MaskPrintf (SYS_DEV, "Cache_Free: freeing '%s' %p\n", cs->name, cs);

	Cache_UnlinkLRU (cs);

	//check_cache ();
	cs->user = 0;
	if (!cs->prev->user) {
		cs->size += cs->prev->size;
		cs->prev->prev->next = cs;
		cs->prev = cs->prev->prev;
	}
	if (!cs->next->user) {
		cs = cs->next;
		cs->size += cs->prev->size;
		cs->prev->prev->next = cs;
		cs->prev = cs->prev->prev;
	}
	if (cs->next == &cache_head) {
		cs->next->prev = cs->prev;
		cs->prev->next = cs->next;
		if (cs->prev != &cache_head)
			Hunk_FreeToHighMark (hunk_size - ((byte*)cs->prev - hunk_base));
		else
			Hunk_FreeToHighMark (0);
	}
	//check_cache ();

	c->data = NULL;
}

VISIBLE void *
Cache_Alloc (cache_user_t *c, int size, const char *name)
{
	cache_system_t *cs;

	if (c->data)
		Sys_Error ("Cache_Alloc: already allocated");

	if (size <= 0)
		Sys_Error ("Cache_Alloc: size %i", size);

	size = (size + sizeof (cache_system_t) + 15) & ~15;

	// find memory for it   
	while (1) {
		cs = Cache_TryAlloc (size, false);
		if (cs) {
			strncpy (cs->name, name, sizeof (cs->name) - 1);
			c->data = (void *) (cs + 1);
			cs->user = c;
			break;
		}
		// free the least recently used cachedat
		if (!Cache_FreeLRU())
			Sys_Error ("Cache_Alloc: out of memory");
	}

	return Cache_Check (c);
}

VISIBLE void
Cache_Report (void)
{
	Sys_MaskPrintf (SYS_DEV, "%4.1f megabyte data cache\n",
					(hunk_size - hunk_high_used -
					 hunk_low_used) / (float) (1024 * 1024));
}

VISIBLE void
Cache_Add (cache_user_t *c, void *object, cache_loader_t loader)
{
	if (c->data || c->object || c->loader)
		Sys_Error ("Cache_Add: cache item already exists!");

	c->object = object;
	c->loader = loader;

//	c->loader (c, Cache_Alloc); // for debugging
}

VISIBLE void
Cache_Remove (cache_user_t *c)
{
	if (!c->object || !c->loader)
		Sys_Error ("Cache_Remove: already removed!");

	if (Cache_Check (c))
		Cache_Free (c);

	c->object = 0;
	c->loader = 0;
}

VISIBLE void *
Cache_TryGet (cache_user_t *c)
{
	void *mem;

	mem = Cache_Check (c);
	if (!mem) {
		c->loader (c->object, Cache_Alloc);
		mem = Cache_Check (c);
	}
	if (mem)
		(((cache_system_t *)c->data) - 1)->readlock++;

	return mem;
}

VISIBLE void *
Cache_Get (cache_user_t *c)
{
	void *mem = Cache_TryGet (c);

	if (!mem)
		Sys_Error ("Cache_Get: couldn't get cache!");
	return mem;
}

VISIBLE void
Cache_Release (cache_user_t *c)
{
	int *readlock;

	readlock = &(((cache_system_t *)c->data) - 1)->readlock;

	if (!*readlock)
		Sys_Error ("Cache_Release: already released!");

	(*readlock)--;

//	if (!*readlock)
//		Cache_Free (c); // for debugging
}

VISIBLE int
Cache_ReadLock (cache_user_t *c)
{
	return (((cache_system_t *)c->data) - 1)->readlock;
}


//============================================================================

VISIBLE void
Memory_Init (void *buf, int size)
{
	hunk_base = buf;
	hunk_size = size;
	hunk_low_used = 0;
	hunk_high_used = 0;

	Cache_Init ();
}