memmgr.c

用C语言实现的DOS操作系统的源代码

/****************************************************************/
/*                                                              */
/*                          memmgr.c                            */
/*                                                              */
/*               Memory Manager for Core Allocation             */
/*                                                              */
/*                      Copyright (c) 1995                      */
/*                      Pasquale J. Villani                     */
/*                      All Rights Reserved                     */
/*                                                              */
/* This file is part of DOS-C.                                  */
/*                                                              */
/* DOS-C 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, or (at your option) any later version.                    */
/*                                                              */
/* DOS-C 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 DOS-C; see the file COPYING.  If not,     */
/* write to the Free Software Foundation, 675 Mass Ave,         */
/* Cambridge, MA 02139, USA.                                    */
/****************************************************************/

#include "../../hdr/portab.h"
#include "globals.h"


/* $Logfile*/
#ifdef VERSION_STRING
static BYTE *memmgrRcsId = "$Header:   C:/dos-c/src/kernel/memmgr.c_v   1.6   04 Jan 1998 23:15:18   patv  $";
#endif

/* $Log:   C:/dos-c/src/kernel/memmgr.c_v  $
 * 
 *    Rev 1.6   04 Jan 1998 23:15:18   patv
 * Changed Log for strip utility
 * 
 *    Rev 1.5   16 Jan 1997 12:47:00   patv
 * pre-Release 0.92 feature additions
 * 
 *    Rev 1.4   29 May 1996 21:03:34   patv
 * bug fixes for v0.91a
 * 
 *    Rev 1.3   19 Feb 1996  3:21:36   patv
 * Added NLS, int2f and config.sys processing
 * 
 *    Rev 1.2   01 Sep 1995 17:54:20   patv
 * First GPL release.
 * 
 *    Rev 1.1   30 Jul 1995 20:51:58   patv
 * Eliminated version strings in ipl
 * 
 *    Rev 1.0   02 Jul 1995  8:33:08   patv
 * Initial revision.
 */
/* $EndLog$ */

VOID mcb_init();        
VOID mcb_print();
VOID show_chain();

/* The following code is 8086 dependant                         */

#ifdef KERNEL
VOID 
mcb_init (mcb FAR *mcbp, UWORD size)
{
	COUNT i;

	mcbp -> m_type = MCB_LAST;
	mcbp -> m_psp = FREE_PSP;
	mcbp -> m_size = size;
	for(i = 0; i < 8; i++)
		mcbp -> m_name[i] = '\0';
	mem_access_mode = FIRST_FIT;
}
#endif

seg 
far2para (VOID FAR *p)
{
	seg u1 = FP_SEG(p);
	offset u2 = FP_OFF(p);
	ULONG phy_addr;

	phy_addr = (((long)u1) << 4) + u2;
	return (phy_addr>>4);
}


seg 
long2para (LONG size)
{
	return ((size + 0x0f)>>4);
}


VOID FAR *
add_far (VOID FAR *fp, ULONG off)
{
	UWORD seg_val;
	UWORD off_val;

	/* Break far pointer into components                            */
	seg_val = FP_SEG(fp);
	off_val = FP_OFF(fp);

	/* add the offset  to the fp's offset part                      */
	off += off_val;

	/* make off_val equal to lower part of new value                */
	off_val = off & 0xffff;

	/* and add top part into seg                                    */
	seg_val += ((off & 0x000f0000l) / 0x10);

	/* and send back the new pointer                                */
	return (VOID FAR *)MK_FP(seg_val, off_val);
}


VOID FAR *
adjust_far (VOID FAR *fp)
{
	ULONG linear;
	UWORD seg_val;
	UWORD off_val;

	/* First, convert the segmented pointer to a linear address     */
	linear = (((ULONG)FP_SEG(fp)) << 4) + FP_OFF(fp);

	/* Break it into segments.                                      */
	seg_val = (UWORD)(linear >> 4);
	off_val = (UWORD)(linear & 0xf);

	/* and return an adddress adjusted to the nearest paragraph     */
	/* boundary.                                                    */
	return MK_FP(seg_val, off_val);
}

#undef REG
#define REG 

#ifdef KERNEL
COUNT 
DosMemAlloc (UWORD size, COUNT mode, seg FAR *para, UWORD FAR *asize)
{
	REG mcb FAR *p;
	mcb FAR *q;
	COUNT i;
	BOOL found;

	/* Initialize                                           */
	p = (mcb FAR *)(MK_FP(first_mcb, 0));

	/* Search through memory blocks                         */
	for(q = (mcb FAR *)0, i = 0, found = FALSE; !found; )
	{
		/* check for corruption                         */
		if(p -> m_type != MCB_NORMAL && p -> m_type != MCB_LAST)
			return DE_MCBDESTRY;

		/* Test if free based on mode rules             */
		switch(mode)
		{
		case LAST_FIT:
		default:
			/* Check for a last fit candidate       */
			if(p -> m_size >= size && p -> m_psp == FREE_PSP)
				/* keep the last know fit       */
				q = p;
			/* not free - bump the pointer          */
			if(p -> m_type != MCB_LAST)
				p = MK_FP(far2para((VOID FAR *)p) + p -> m_size + 1, 0);
			/* was there no room (q == 0)?          */
			else if(p -> m_type == MCB_LAST && q == (mcb FAR *)0)
				return DE_NOMEM;
			/* something was found - continue       */
			else
				found = TRUE;
			break;

		case FIRST_FIT:
			/* Check for a first fit candidate      */
			if(p -> m_size >= size && p -> m_psp == FREE_PSP)
			{
				q = p;
				found = TRUE;
				break;
			}
			/* not free - bump the pointer          */
			if(p -> m_type != MCB_LAST)
				p = MK_FP(far2para((VOID FAR *)p) + p -> m_size + 1, 0);
			/* nothing found till end - no room     */
			else
				return DE_NOMEM;
			break;

		case BEST_FIT:
			/* Check for a best fit candidate       */
			if(p -> m_size >= size && p -> m_psp == FREE_PSP)
			{
				if(i == 0 || p -> m_size < i)
				{
					i = p -> m_size;
					q = p;
				}
			}
			/* not free - bump the pointer          */
			if(p -> m_type != MCB_LAST)
				p = MK_FP(far2para((VOID FAR *)p) + p -> m_size + 1, 0);
			/* was there no room (q == 0)?          */
			else if(p -> m_type == MCB_LAST && q == (mcb FAR *)0)
				return DE_NOMEM;
			/* something was found - continue       */
			else
				found = TRUE;
			break;

		case LARGEST:
			/* Check for a first fit candidate      */
			if((p -> m_psp == FREE_PSP) && (i == 0 || p -> m_size > i))
			{
				size = *asize = i = p -> m_size;
				q = p;
			}
			/* not free - bump the pointer          */
			if(p -> m_type != MCB_LAST)
				p = MK_FP(far2para((VOID FAR *)p) + p -> m_size + 1, 0);
			/* was there no room (q == 0)?          */
			else if(p -> m_type == MCB_LAST && q == (mcb FAR *)0)
				return DE_NOMEM;
			/* something was found - continue       */
			else
				found = TRUE;
			break;
		}
	}
	p = q;
	/* Larger fit case              */
	if(p -> m_size > size)
	{
		if(mode != LAST_FIT)
		{
			q = MK_FP(far2para((VOID FAR *)p) + size + 1, 0);
			/* Always flow m_type up */
			/* on alloc             */
			q -> m_type = p -> m_type;
			p -> m_type = MCB_NORMAL;
			p -> m_psp = cu_psp;
			q -> m_psp = FREE_PSP;
			q -> m_size = p -> m_size - size - 1;
			p -> m_size = size;
			for(i = 0; i < 8; i++)
				p -> m_name[i] = q -> m_name[i] = '\0';
		}
		else
		{
			q = MK_FP(far2para((VOID FAR *)p) + (p -> m_size - size), 0);
			/* Always flow m_type up */
			/* on alloc             */
			q -> m_type = p -> m_type;
			p -> m_type = MCB_NORMAL;
			q -> m_psp = cu_psp;
			p -> m_psp = FREE_PSP;
			p -> m_size = p -> m_size - size - 1;
			q -> m_size = size;
			for(i = 0; i < 8; i++)
				p -> m_name[i] = q -> m_name[i] = '\0';
		}
		/* Found - return good          */
		*para = far2para((VOID FAR *)(mode == LAST_FIT ? (VOID FAR *)q : (VOID FAR *)p));
		return SUCCESS;
	}
	/* Exact fit case               */
	else if(p -> m_size == size)
	{
		p -> m_psp = cu_psp;
		for(i = 0; i < 8; i++)
			p -> m_name[i] = '\0';
		/* Found - return good          */
		*para = far2para((VOID FAR *)(BYTE FAR *)p);
		return SUCCESS;
	}
	else
		return DE_MCBDESTRY;
}


seg 
DosMemLargest (seg FAR *size)
{
	REG mcb FAR *p;
	mcb FAR *q;
	COUNT found;