id_mm.c

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// NEWMM.C

/*
=============================================================================

		   ID software memory manager
		   --------------------------

Primary coder: John Carmack

RELIES ON
---------
Quit (char *error) function


WORK TO DO
----------
MM_SizePtr to change the size of a given pointer

Multiple purge levels utilized

EMS / XMS unmanaged routines

=============================================================================
*/

#include "ID_HEADS.H"
#pragma hdrstop

#pragma warn -pro
#pragma warn -use

/*
=============================================================================

							LOCAL INFO

=============================================================================
*/

#define LOCKBIT		0x80	// if set in attributes, block cannot be moved
#define PURGEBITS	3		// 0-3 level, 0= unpurgable, 3= purge first
#define PURGEMASK	0xfffc
#define BASEATTRIBUTES	0	// unlocked, non purgable

#define MAXUMBS		10

typedef struct mmblockstruct
{
	unsigned	start,length;
	unsigned	attributes;
	memptr		*useptr;	// pointer to the segment start
	struct mmblockstruct far *next;
} mmblocktype;


//#define GETNEWBLOCK {if(!(mmnew=mmfree))Quit("MM_GETNEWBLOCK: No free blocks!")\
//	;mmfree=mmfree->next;}

#define GETNEWBLOCK {if(!mmfree)MML_ClearBlock();mmnew=mmfree;mmfree=mmfree->next;}

#define FREEBLOCK(x) {*x->useptr=NULL;x->next=mmfree;mmfree=x;}

/*
=============================================================================

						 GLOBAL VARIABLES

=============================================================================
*/

mminfotype	mminfo;
memptr		bufferseg;
boolean		mmerror;

void		(* beforesort) (void);
void		(* aftersort) (void);

/*
=============================================================================

						 LOCAL VARIABLES

=============================================================================
*/

boolean		mmstarted;

void far	*farheap;
void		*nearheap;

mmblocktype	far mmblocks[MAXBLOCKS]
			,far *mmhead,far *mmfree,far *mmrover,far *mmnew;

boolean		bombonerror;

//unsigned	totalEMSpages,freeEMSpages,EMSpageframe,EMSpagesmapped,EMShandle;

void		(* XMSaddr) (void);		// far pointer to XMS driver

unsigned	numUMBs,UMBbase[MAXUMBS];

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

//
// local prototypes
//

boolean		MML_CheckForEMS (void);
void 		MML_ShutdownEMS (void);
void 		MM_MapEMS (void);
boolean 	MML_CheckForXMS (void);
void 		MML_ShutdownXMS (void);
void		MML_UseSpace (unsigned segstart, unsigned seglength);
void 		MML_ClearBlock (void);

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

/*
======================
=
= MML_CheckForXMS
=
= Check for XMM driver
=
=======================
*/

boolean MML_CheckForXMS (void)
{
	numUMBs = 0;

asm {
	mov	ax,0x4300
	int	0x2f				// query status of installed diver
	cmp	al,0x80
	je	good
	}

	return false;
good:
	return true;
}


/*
======================
=
= MML_SetupXMS
=
= Try to allocate all upper memory block
=
=======================
*/

void MML_SetupXMS (void)
{
	unsigned	base,size;

asm	{
	mov	ax,0x4310
	int	0x2f
	mov	[WORD PTR XMSaddr],bx
	mov	[WORD PTR XMSaddr+2],es		// function pointer to XMS driver
	}

getmemory:
asm	{
	mov	ah,XMS_ALLOCUMB
	mov	dx,0xffff					// try for largest block possible
	call	[DWORD PTR XMSaddr]
	or	ax,ax
	jnz	gotone

	cmp	bl,0xb0						// error: smaller UMB is available
	jne	done;

	mov	ah,XMS_ALLOCUMB
	call	[DWORD PTR XMSaddr]		// DX holds largest available UMB
	or	ax,ax
	jz	done						// another error...
	}

gotone:
asm	{
	mov	[base],bx
	mov	[size],dx
	}
	MML_UseSpace (base,size);
	mminfo.XMSmem += size*16;
	UMBbase[numUMBs] = base;
	numUMBs++;
	if (numUMBs < MAXUMBS)
		goto getmemory;

done:;
}


/*
======================
=
= MML_ShutdownXMS
=
======================
*/

void MML_ShutdownXMS (void)
{
	int	i;
	unsigned	base;

	for (i=0;i<numUMBs;i++)
	{
		base = UMBbase[i];

asm	mov	ah,XMS_FREEUMB
asm	mov	dx,[base]
asm	call	[DWORD PTR XMSaddr]
	}
}

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

/*
======================
=
= MML_UseSpace
=
= Marks a range of paragraphs as usable by the memory manager
= This is used to mark space for the near heap, far heap, ems page frame,
= and upper memory blocks
=
======================
*/

void MML_UseSpace (unsigned segstart, unsigned seglength)
{
	mmblocktype far *scan,far *last;
	unsigned	oldend;
	long		extra;

	scan = last = mmhead;
	mmrover = mmhead;		// reset rover to start of memory

//
// search for the block that contains the range of segments
//
	while (scan->start+scan->length < segstart)
	{
		last = scan;
		scan = scan->next;
	}

//
// take the given range out of the block
//
	oldend = scan->start + scan->length;
	extra = oldend - (segstart+seglength);
	if (extra < 0)
		Quit ("MML_UseSpace: Segment spans two blocks!");

	if (segstart == scan->start)
	{
		last->next = scan->next;			// unlink block
		FREEBLOCK(scan);
		scan = last;
	}
	else
		scan->length = segstart-scan->start;	// shorten block

	if (extra > 0)
	{
		GETNEWBLOCK;
		mmnew->useptr = NULL;

		mmnew->next = scan->next;
		scan->next = mmnew;
		mmnew->start = segstart+seglength;
		mmnew->length = extra;
		mmnew->attributes = LOCKBIT;
	}

}

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

/*
====================
=
= MML_ClearBlock
=
= We are out of blocks, so free a purgable block
=
====================
*/

void MML_ClearBlock (void)
{
	mmblocktype far *scan,far *last;

	scan = mmhead->next;

	while (scan)
	{
		if (!(scan->attributes&LOCKBIT) && (scan->attributes&PURGEBITS) )
		{
			MM_FreePtr(scan->useptr);
			return;
		}
		scan = scan->next;
	}

	Quit ("MM_ClearBlock: No purgable blocks!");
}


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

/*
===================
=
= MM_Startup
=
= Grabs all space from turbo with malloc/farmalloc
= Allocates bufferseg misc buffer
=
===================
*/

static	char *ParmStrings[] = {"noems","noxms",""};

void MM_Startup (void)
{
	int i;
	unsigned 	long length;
	void far 	*start;
	unsigned 	segstart,seglength,endfree;

	if (mmstarted)
		MM_Shutdown ();


	mmstarted = true;
	bombonerror = true;
//
// set up the linked list (everything in the free list;
//
	mmhead = NULL;
	mmfree = &mmblocks[0];
	for (i=0;i<MAXBLOCKS-1;i++)
		mmblocks[i].next = &mmblocks[i+1];
	mmblocks[i].next = NULL;

//
// locked block of all memory until we punch out free space
//
	GETNEWBLOCK;
	mmhead = mmnew;				// this will allways be the first node
	mmnew->start = 0;
	mmnew->length = 0xffff;
	mmnew->attributes = LOCKBIT;
	mmnew->next = NULL;
	mmrover = mmhead;


//
// get all available near conventional memory segments
//
	length=coreleft();
	start = (void far *)(nearheap = malloc(length));

	length -= 16-(FP_OFF(start)&15);
	length -= SAVENEARHEAP;
	seglength = length / 16;			// now in paragraphs
	segstart = FP_SEG(start)+(FP_OFF(start)+15)/16;
	MML_UseSpace (segstart,seglength);
	mminfo.nearheap = length;

//
// get all available far conventional memory segments
//
	length=farcoreleft();
	start = farheap = farmalloc(length);
	length -= 16-(FP_OFF(start)&15);
	length -= SAVEFARHEAP;
	seglength = length / 16;			// now in paragraphs
	segstart = FP_SEG(start)+(FP_OFF(start)+15)/16;
	MML_UseSpace (segstart,seglength);
	mminfo.farheap = length;
	mminfo.mainmem = mminfo.nearheap + mminfo.farheap;

//
// allocate the misc buffer
//
	mmrover = mmhead;		// start looking for space after low block

	MM_GetPtr (&bufferseg,BUFFERSIZE);
}

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

/*
====================
=
= MM_Shutdown
=
= Frees all conventional, EMS, and XMS allocated
=
====================
*/

void MM_Shutdown (void)
{
  if (!mmstarted)
	return;

  farfree (farheap);
  free (nearheap);
//  MML_ShutdownXMS ();
}

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

/*
====================
=
= MM_GetPtr
=
= Allocates an unlocked, unpurgable block
=
====================
*/

void MM_GetPtr (memptr *baseptr,unsigned long size)
{
	mmblocktype far *scan,far *lastscan,far *endscan
				,far *purge,far *next;
	int			search;
	unsigned	needed,startseg;

	needed = (size+15)/16;		// convert size from bytes to paragraphs

	GETNEWBLOCK;				// fill in start and next after a spot is found
	mmnew->length = needed;
	mmnew->useptr = baseptr;
	mmnew->attributes = BASEATTRIBUTES;

tryagain:
	for (search = 0; search<3; search++)
	{
	//
	// first search:	try to allocate right after the rover, then on up
	// second search: 	search from the head pointer up to the rover
	// third search:	compress memory, then scan from start
		if (search == 1 && mmrover == mmhead)
			search++;

		switch (search)
		{
		case 0:
			lastscan = mmrover;
			scan = mmrover->next;
			endscan = NULL;
			break;
		case 1:
			lastscan = mmhead;
			scan = mmhead->next;
			endscan = mmrover;
			break;
		case 2:
			MM_SortMem ();
			lastscan = mmhead;
			scan = mmhead->next;
			endscan = NULL;
			break;
		}