268 lines
7.8 KiB
NASM
268 lines
7.8 KiB
NASM
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name PROSMMU
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title Scheme Memory Management Utilities for Protected Mode
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page 62,132
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; =====> PROSMMU.ASM
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;****************************************************************
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;* TIPC Scheme '84 Memory Management Utilities *
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;* *
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;* (C) Copyright 1985 by Texas Instruments Incorporated. *
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;* All rights reserved. *
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;* *
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;* Author: Terry Caudill *
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;* Date written: 17 Feb 1987 *
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;****************************************************************
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include schemed.equ
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include schemed.ref
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include schemed.mac
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DOS equ 021h
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DGROUP group data
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PGROUP group prog
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data segment word public 'DATA'
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assume ds:DGROUP
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extrn page0:byte, page4:byte, page5:byte, page6:byte
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extrn page7:byte, page8:byte
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extrn _top:word, _paras:word,first_pa:word,first_dos:word
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public scheme_heap,gc_ing
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scheme_heap dw 0 ;selector for entire scheme heapspace
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gc_ing dw 0 ;denotes when gc is taking place
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sub_segerr db "Error allocating data segment",0Ah,0
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alloc_err db "Unable to allocate memory for scheme heap",0Ah,0
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data ends
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prog segment byte public 'PROG'
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assume cs:PGROUP
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;;======================================================================
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;;
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;; Get page base address of page
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;;
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;;======================================================================
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public getbase
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getbase proc near
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push BP
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mov BP,SP
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mov BX,word ptr [BP+4]
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mov AX,word ptr [BX+pagetabl] ;; Get table indicator
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pop BP
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ret
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getbase endp
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;;======================================================================
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;;
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;; InitMem()
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;; Compute the best page size, but not smaller than MIN_PAGESIZE
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;;
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;;======================================================================
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public InitMem
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InitMem proc near
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push BP
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sub SP,2 ;; Allocate loacl storage
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mov BP,SP
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mov word ptr [bp+0],0 ;; number of pages allocated
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mov bx,ds
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mov es,bx ;; ensure ES = DS
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;; The first eight pagetable entries contain offsets to data within
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;; the local data segment. These offsets must be changed to to
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;; selectors so that they can be accessed as any other scheme object.
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;; Convert offset within pagetabl[0] into paragraph address
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mov di,offset pagetabl
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xor si,si
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mov bx,word ptr [di] ;; si:bx = offset within DS
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xor cx,cx
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mov dx,16 ;; cx:dx = length
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mov ax,0E801h ;; Create Data Window
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int DOS
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jc subsegerr
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mov word ptr [di],ax ;; move selector into pagetabl
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;; Now convert pagetabl[4] through pagetabl[8]
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mov dx,5 ;; dx = # entries to modify
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mov di,offset pagetabl[8]
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EmmP$0:
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push dx
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mov bx,word ptr [di] ;; si:bx = offset within ds
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xor cx,cx ;; cx:dx = length
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mov dx,0600h ;; (big enough for largest page)
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mov ax,0E801h ;; Create Data Window
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int DOS
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pop dx ;; get # entries
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jc subsegerr
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mov word ptr [di],ax ;; move selector into pagetabl
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add di,2 ;; address next pagetable entry
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dec dx ;; any remaining?
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jnz EmmP$0 ;; yes, loop
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jmp around_error
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subsegerr:
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lea bx,sub_segerr
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jmp FatalError
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around_error:
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;; Now we must allocate the remaining memory (to approx. 4mb), and fill
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;; the remaining pagetabl entries with selectors to address each page.
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;; ask for too much memory, # bytes available will be returned in cx:dx
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mov cx,0ffffh
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mov dx,0ffffh ;; cx:dx = # bytes requested
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mov ax,0E800h ;; create data segment
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int 021h ;; extended dos function from AIA
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mov ax,dx
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mov dx,cx ;; dx:ax = # bytes available
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push ax
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push dx ;; save for later
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;; calculate #paragraphs available
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mov cx,4 ;; cx = shift count
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make_para:
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shr dx,1
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rcr ax,1
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loop make_para
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;; lets make the pagesize a multiple of 2000h bytes (this is so that when
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;; pages must be merged to hold large objects, there will be no wasted
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;; space).
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mov cx,NUMPAGES-PreAlloc ;; cx = number pagetabl entrys available
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idiv cx
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mov bx,ax ;; bx = # paras per page
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mov ax,200h
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cmp ax,bx ;; if #paras/page < 200 paras
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jge make_pagesize ;; round to 200, jump
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mov ax,400h ;; if #paras/page < 400 paras
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cmp ax,bx ;; round to 400, jump
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jge make_pagesize
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mov ax,7FFh ;; default pagesize to 7FF0 bytes
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;; change the paras used in calculations above to bytes
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make_pagesize:
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mov cx,4
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shl ax,cl ;; dx = number bytes per page
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mov pagesize,ax ;; save away in pagesize
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;; divide the # bytes available by the #bytes/page to see how many
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;; pages will be required. max = NUMPAGES-PreAlloc
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mov cx,ax ;; cx = # bytes/page
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pop dx
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pop ax ;; dx:ax = # bytes available
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idiv cx ;; ax = # pages required
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cmp ax,NUMPAGES-PreAlloc ;; do we exceed number avail page?
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jle Emmp$0a ;; no, jump
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mov ax,NUMPAGES-PreAlloc ;; yes, just fill the table
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Emmp$0a:
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xor dx,dx
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mul cx ;; dx:ax = total memory rquirements
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;; Allocate only enough memory for the pagetable. Initially allocate just
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;; one segment large enough to hold all the scheme heap.
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push cx ;;tempsave bytes/page
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mov cx,dx
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mov dx,ax ;; cx:dx = length
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mov ax,0E800h ;; Create Data Segment
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int DOS
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pop bx ;;restore bytes/page
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jnc Emmp$0b
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allocerr:
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lea bx,alloc_err
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jmp FatalError
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Emmp$0b:
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mov scheme_heap,ax ;; save selector to scheme heap
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;; Now allocate multiple "windows" within this larger segment. The pages
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;; may overlap so that we can merge pages to hold objects that are larger
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;; than a single page. In AI Archiects terminology, we will allocate
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;; "pages" of 8000h (large enough for our largest object) with a "stride"
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;; of our desired pagesize (this causes overlap every pagesize number of
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;; bytes. The call below will return a selector to the starting page,
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;; and the number of selectors necessary to cover the entire segment.
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;;
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;; Warning: ds register does not address our data segment below
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;;
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mov ds,ax ;; ds = large segment
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xor cx,cx
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mov dx,08000h ;; cx:dx = size of each page
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xor si,si ;; si:bx = stride
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push bx ;; save page size
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mov AX,0EA00h ;; Allocate Multiple Windows
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int DOS ;; extended Dos func from AIA
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pop si ;; restore page size
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push ss
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pop ds
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jc allocerr ;; if error, exit
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;;
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;; Warning: ds register does not address our data segment above
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;;
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;; ax = first selector, bx = number of selectors, si=page size
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;; loop number of selector times, filling the pagetabl with
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;; selectors to the memory. selectors are 8 bytes in length
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;; so bump each selector by 8 to get to the next one.
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mov dx,nextpage ;; Next page table entry
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mov freepage,dx ;; is also next free page
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mov first_pa,dx ;; save for rlsexp, sbid
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mov cx,bx ;; cx = number of pages to fill
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jcxz Emmp$2 ;; if no pages, jump
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EmmP$1:
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mov bx,dx
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shl bx,1 ;; bx = page index
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mov word ptr ss:pagetabl[BX],AX ;; Save selector in table
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and word ptr ss:attrib[BX],not NOMEMORY ;; mark as allocated
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mov word ptr ss:psize[BX],si ;; note its size
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inc dx ;; and update for next page
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mov word ptr ss:pagelink[BX],dx ;; update page link
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mov word ptr ss:nextcell[BX],0 ;; clear free chain pointer
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inc word ptr [bp+0] ;; page_count++
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add ax,8 ;; next selector
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loop EmmP$1 ;; get next selector
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EmmP$2:
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mov nextpage,dx ;; set up nextpage
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mov lastpage,dx ;; lastpage = nextpage
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pop ax ;; return number pages allocated
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pop bp
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ret
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FatalError:
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mov ax,ss ;; ensure ds=es=ss
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mov ds,ax
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mov es,ax
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push bx ;; push error message
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C_call print_an ;; print message and quit
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InitMem endp
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;;======================================================================
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;;
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;; rlsexp - Release Dos Allocated Pages
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;;
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;;======================================================================
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public rlsexp
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rlsexp proc near
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push ES
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push BP
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mov BP,SP
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mov es,scheme_heap ;; es = slector for scheme heap
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mov AX,4900h ;; free allocated memory
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int DOS ;; do it
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pop BP
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pop ES
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ret
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rlsexp endp
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prog ends
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end
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