252 lines
6.7 KiB
NASM
252 lines
6.7 KiB
NASM
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; Copyright (c) Mix Software 1988
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;
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; --------------------------------------------------
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; _fmalloc - allocate from far heap
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; if no memory available, allocate from near heap
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; char far *_fmalloc(size)
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; unsigned size;
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; --------------------------------------------------
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;
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IDT _fmalloc
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DEF _fmalloc
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FREF falloc
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FREF malloc
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;
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_fmalloc MOV SI,SP
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PUSH [SI][%PARM1-2]
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CALLFAR falloc
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ADD SP,%2
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MOV CX,DX
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OR CX,AX
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JNZ OK
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MOV SI,SP
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PUSH [SI][%PARM1-2]
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CALLFAR malloc
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ADD SP,%2
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TEST AX,AX
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JZ NULL
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MOV DX,DS
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OK RETSEG
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NULL XOR DX,DX
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RETSEG
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END
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;
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; --------------------------------------------------
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; _ffree - release from near or far heap
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; void _ffree(ptr)
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; char far *ptr;
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; --------------------------------------------------
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;
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IDT _ffree
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DEF _ffree
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FREF ffree
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FREF free
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;
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_ffree MOV SI,SP
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MOV AX,[SI][%PARM2-2]
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MOV CX,DS
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CMP AX,CX
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JZ NEAR
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PUSH AX
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PUSH [SI][%PARM1-2]
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CALLFAR ffree
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ADD SP,%4
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RETSEG
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NEAR PUSH [SI][%PARM1-2]
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CALLFAR free
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ADD SP,%2
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RETSEG
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END
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;
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; --------------------------------------------------
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; _nmsize - return the size of a memory block
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; unsigned _nmsize(ptr)
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; char near *ptr;
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; --------------------------------------------------
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;
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IDT _nmsize
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DEF _nmsize
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DEF _msize
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;
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_msize EQU $
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_nmsize MOV SI,SP
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MOV BX,[SI][%PARM1-2]
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MOV AX,[BX][%-2] ; get size and allocated flag
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AND AX,>FFFE
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SUB AX,%2
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RETSEG
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END
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;
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; --------------------------------------------------
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; _memavl - return the byte count of available memory
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; unsigned _memavl()
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; --------------------------------------------------
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;
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IDT _memavl
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REF $$CURH
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REF $$HMIN
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REF $$HMAX
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DEF _memavl
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;
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_memavl MOV AX,[$$HMAX]
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SUB AX,[$$HMIN]
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SUB AX,[$$CURH]
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SUB AX,6
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RETSEG
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END
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;
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; --------------------------------------------------
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; coreleft - return the byte count of available memory
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; unsigned coreleft()
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; --------------------------------------------------
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;
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IDT coreleft
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REF $$CURH
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REF $$HMIN
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REF $$HMAX
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DEF coreleft
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;
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coreleft MOV AX,[$$HMAX]
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SUB AX,[$$HMIN]
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SUB AX,[$$CURH]
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SUB AX,6
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RETSEG
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END
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;
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; --------------------------------------------------
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; _freect - return the number of items in heap
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; unsigned _freect(size)
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; unsigned size;
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; --------------------------------------------------
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;
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IDT _freect
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REF $$CURH
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REF $$HMIN
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REF $$HMAX
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DEF _freect
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;
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_freect MOV AX,[$$HMAX]
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SUB AX,[$$HMIN]
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SUB AX,[$$CURH]
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SUB AX,6
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MOV BX,SP
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MOV BX,[BX][%PARM1-2]
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XOR DX,DX
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TEST BX,BX
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JZ EXIT
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DIV BX
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EXIT RETSEG
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END
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;
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; --------------------------------------------------
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; _expand - expand a block of memory without moving it
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; _expand(ptr,size)
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; char *ptr;
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; unsigned size; /* requested new size */
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; --------------------------------------------------
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;
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IDT _expand
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DEF _expand
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IF UPPER
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DEF _EXPAND
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ENDIF
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REF $$FREE
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REF $$CURH
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REF $$MAXH
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FREF free
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;
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_EXPAND EQU $
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_expand PUSH BP
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MOV BP,SP
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MOV BX,[BP][%PARM1]
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MOV CX,[BX][%-2] ; get size and allocated flag
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TEST CX,>0001
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JZ AVAIL
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SUB CX,%3 ; remove flag and overhead
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CMP CX,[BP][%PARM2]
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JB EXPAND ; Make larger
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;
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; Try to shrink the block
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; If shrink is by at least 6 bytes, create a new pointer
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; and use free to release it.
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;
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SHRINK SUB CX,[BP][%PARM2]
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NEG CX
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AND CX,>FFFE ; Must be an even number
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CMP CX,%6
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JB FREEOK ; Not enough to free
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SUB [BX][%-2],CX ; Remove from this block count
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ADD BX,[BX][%-2] ; Point to end of block
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DEC BX ; remove allocated flag
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INC CX
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MOV [BX][%-2],CX ; create allocated block header
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PUSH BX
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CALLFAR free
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POP BX
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MOV AX,[BP][%PARM1]
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POP BP
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RETSEG
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;
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; Try to expand the block.
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; the next higher block must be free
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;
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EXPAND MOV SI,[$$FREE] ; Start of free list
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MOV DX,SI
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ADD BX,CX ; Point to next block header
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SEARCH CMP SI,BX ; Found next block?
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JZ FOUND
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MOV SI,[SI][%2] ; Move to next free block
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CMP SI,DX ; Full circuit?
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JNZ SEARCH
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JMPS NULLEXIT ; unable to expand
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FOUND CMP [SI],6
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JBE NULLEXIT ; protect anchor
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MOV DI,[SI][%4] ; predecessor
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MOV BX,[SI][%2] ; successor
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MOV [DI][%2],BX
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MOV [BX][%4],DI ; block linked out
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MOV CX,[SI] ; length of the free block
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ADD [$$CURH],CX
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MOV AX,[$$CURH]
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CMP AX,[$$MAXH]
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JBE ADJUST
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MOV [$$MAXH],AX
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ADJUST MOV BX,[BP][%PARM1] ; merge block
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ADD CX,[BX][%-2]
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MOV [BX][%-2],CX ; Blocks are merged
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SUB CX,%3
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JMPS SHRINK ; Return the excess
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;
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; Block is free - it has therefore already become as large as
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; possible. Check size to generate return value
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;
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AVAIL SUB CX,%2
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CMP CX,[BP][%PARM2]
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JAE FREEOK ; Large enough
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NULLEXIT XOR AX,AX
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POP BP
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RETSEG
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FREEOK MOV AX,BX
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POP BP
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RETSEG
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END
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;
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; --------------------------------------------------
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; heapsiz - return the byte count of available memory
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; unsigned heapsiz()
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; --------------------------------------------------
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;
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IDT heapsiz
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REF $$CURH
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REF $$HMIN
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REF $$HMAX
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DEF heapsiz
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;
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heapsiz MOV AX,[$$HMAX]
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SUB AX,[$$HMIN]
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SUB AX,[$$CURH]
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SUB AX,6
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RETSEG
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END
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