414 lines
7.8 KiB
NASM
414 lines
7.8 KiB
NASM
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; mem.asm:
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;
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; masm -Mx -Zi -DSEGNAME=????? asm.asm
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;
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TITLE MEM.ASM
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;****************************************************************
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;* MEM.ASM - Assembly mem-copy routines *
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;* for 80286 and 80386 *
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;****************************************************************
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;
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?PLM=1 ; PASCAL Calling convention is DEFAULT
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?WIN=0 ; Windows calling convention
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PMODE=1
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.xlist
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include cmacros.inc
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include windows.inc
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.list
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externA __WinFlags ; in KERNEL
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externA __AHINCR ; in KERNEL
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externA __AHSHIFT ; in KERNEL
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; The following structure should be used to access high and low
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; words of a DWORD. This means that "word ptr foo[2]" -> "foo.hi".
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LONG struc
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lo dw ?
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hi dw ?
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LONG ends
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FARPOINTER struc
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off dw ?
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sel dw ?
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FARPOINTER ends
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; -------------------------------------------------------
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; DATA SEGMENT DECLARATIONS
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; -------------------------------------------------------
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ifndef SEGNAME
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SEGNAME equ <_TEXT>
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endif
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createSeg %SEGNAME, CodeSeg, word, public, CODE
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sBegin Data
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sEnd Data
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sBegin CodeSeg
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assumes cs,CodeSeg
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assumes ds,DATA
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;---------------------------Public-Routine------------------------------;
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; hmemcpy
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;
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; copy memory
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;
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; Entry:
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; lpSrc HPSTR to copy from
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; lpDst HPSTR to copy to
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; cbMem DWORD count of bytes to move
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;
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; NOTE: overlapped copies will work iff lpSrc.sel == lpDst.sel
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; [This is a lie. They will always work.]
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;
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; Returns:
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; destination pointer
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; Error Returns:
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; None
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; Registers Preserved:
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; BP,DS,SI,DI
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; Registers Destroyed:
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; AX,BX,CX,DX,FLAGS
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; Calls:
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; nothing
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; History:
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;
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; Wed 04-Jan-1990 13:45:58 -by- Todd Laney [ToddLa]
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; Created.
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; Tue 16-Oct-1990 16:41:00 -by- David Maymudes [DavidMay]
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; Modified 286 case to work correctly with cbMem >= 64K.
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; Changed name to hmemcpy.
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; Changed 386 case to copy by longwords
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;-----------------------------------------------------------------------;
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cProc MemCopy,<FAR,PASCAL,PUBLIC,NODATA>,<>
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; ParmD lpDst
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; ParmD lpSrc
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; ParmD cbMem
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cBegin <nogen>
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mov ax,__WinFlags
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test ax,WF_CPU286
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jz fmemcpy386
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jmp FAR PTR fmemcpy286
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cEnd <nogen>
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cProc fmemcpy386,<FAR,PASCAL,PUBLIC,NODATA>,<ds>
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ParmD lpDst
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ParmD lpSrc
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ParmD cbMem
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cBegin
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.386
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push edi
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push esi
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cld
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mov ecx,cbMem
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jecxz mc386_exit
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movzx edi,di
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movzx esi,si
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lds si,lpSrc
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les di,lpDst
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;
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; calculate differance of pointers in "selector" space
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;
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mov ax,si ; DX:AX = lpSrc
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mov dx,ds
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mov bx,es ; BX = selector of ptr B
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mov cx,__AHSHIFT ; number of selector bits per 64K 'segment'
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shr dx,cl ; linearize ptr A
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shr bx,cl ; linearize ptr B
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;
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; DX and BX contain normalized selectors
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;
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mov ecx,cbMem
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sub ax,di
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sbb dx,bx ; do long subtraction.
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jnc mc_copy_forward
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add ax,cx
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adc dx,cbMem.hi
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jnc mc_copy_forward ; carry, so >0, thus they do hit.
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std
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add edi,ecx
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add esi,ecx
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sub edi,4
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sub esi,4
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push ecx
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shr ecx,2 ; get count in DWORDs
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rep movs dword ptr es:[edi], dword ptr ds:[esi]
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db 67H ; Fix strange 386 bug
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add edi,3
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add esi,3
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pop ecx
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and ecx,3
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rep movs byte ptr es:[edi], byte ptr ds:[esi]
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db 67H ; Fix strange 386 bug
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jmp mc386_exit
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mc_copy_forward:
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push ecx
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shr ecx,2 ; get count in DWORDs
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rep movs dword ptr es:[edi], dword ptr ds:[esi]
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db 67H
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pop ecx
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and ecx,3
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rep movs byte ptr es:[edi], byte ptr ds:[esi]
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db 67H
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nop
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mc386_exit:
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cld
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pop esi
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pop edi
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mov dx,lpDst.sel ; return destination address
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mov ax,lpDst.off
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.286
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cEnd
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cProc fmemcpy286,<FAR,PASCAL,PUBLIC,NODATA>,<ds,si,di>
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ParmD lpDst
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ParmD lpSrc
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ParmD cbMem
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cBegin
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mov cx,cbMem.lo ; CX holds count
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or cx,cbMem.hi ; or with high word
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jnz @f
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jmp empty_copy
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@@:
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lds si,lpSrc ; DS:SI = src
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les di,lpDst ; ES:DI = dst
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;
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; calculate differance of pointers in "selector" space
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;
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mov ax,si ; DX:AX = lpSrc
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mov dx,ds
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mov bx,es ; BX = selector of ptr B
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mov cx,__AHSHIFT ; number of selector bits per 64K 'segment'
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shr dx,cl ; linearize ptr A
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shr bx,cl ; linearize ptr B
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;
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; DX and BX contain normalized selectors
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;
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mov cx,cbMem.lo
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sub ax,di
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sbb dx,bx ; do long subtraction.
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jnc forward_copy ; difference is positive, so copy forward
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; see if the blocks intersect: is source + count > dest?
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; equivalently, is source-dest + count > 0 ?
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; sub ax,cx
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; sbb dx,0
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; jnc next ; This looks wrong. Recheck!
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add ax,cx
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adc dx,cbMem.hi
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jc reverse_copy ; carry, so >0, thus they do hit.
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forward_copy:
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jmp next
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reverse_copy:
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; first, we have to set ds:si and es:di to the _ends_ of the blocks
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sub cx,1
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sbb cbMem.hi,0 ; subtract 2 from (long) count
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xor ax,ax
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add si,cx
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adc ax,cbMem.hi
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push cx
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mov cx,__AHSHIFT
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shl ax,cl
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pop cx
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mov bx,ds
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add ax,bx ; advance DS
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mov ds,ax
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xor ax,ax
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add di,cx
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adc ax,cbMem.hi
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push cx
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mov cx,__AHSHIFT
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shl ax,cl
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pop cx
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mov bx,es
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add ax,bx ; advance ES
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mov es,ax
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add cx,1
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adc cbMem.hi,0 ; restore count
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;
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; DS:SI += Count
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; ES:DI += Count
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; While Count != 0 Do
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; Num = MIN(Count,SI+1,DI+1)
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; Reverse Copy "Num" Bytes from DS:SI to ES:DI
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; (SI -= Num, DI -= Num)
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; Count -= Num
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; If Count == 0 Then
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; BREAK
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; If SI == 0xFFFF Then
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; DS -= __AHINCR
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; If DI == 0xFFFF Then
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; ES -= __AHINCR
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;
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next_r:
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mov ax,si
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sub ax,di
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sbb bx,bx
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and ax,bx
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add ax,di ; AX = MIN(SI, DI)
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test cbMem.hi,-1 ; is high word not zero?
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jnz @f ; at least 64k to go
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dec cx
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sub ax,cx
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sbb bx,bx
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and ax,bx
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add ax,cx
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inc cx
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@@:
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xor bx,bx
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add ax,1 ; AX = Num = MIN(Count-1,SI,DI)+1
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adc bx,0 ; bx==1 if exactly 64k
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xchg ax,cx
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sub ax,cx ; Count -= Num
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sbb cbMem.hi,bx
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std
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shr bx,1
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rcr cx,1 ; if bx==1, then cx ends up 0x8000
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dec si
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dec di
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rep movsw
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inc si ; realign pointers
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inc di
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adc cl,cl
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rep movsb ; move last byte, if necessary
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cld
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mov cx,ax ; restore cx
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or ax,cbMem.hi
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jz done ; If Count == 0 Then BREAK
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cmp si,-1 ; if SI wraps, update DS
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jne @f
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mov ax,ds
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sub ax,__AHINCR
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mov ds,ax ; update DS if appropriate
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@@:
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cmp di,-1 ; if DI wraps, update ES
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jne next_r
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mov ax,es
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sub ax,__AHINCR
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mov es,ax ; update ES if appropriate
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jmp next_r
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;
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; While Count != 0 Do
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; If (Count + SI > 65536) OR (Count + DI > 65536) Then
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; Num = Min(65536-SI, 65536-DI)
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; Else
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; Num = Count
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; Copy "Num" Bytes from DS:SI to ES:DI (SI += Num, DI += Num)
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; Count -= Num
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; If Count == 0 Then
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; BREAK
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; If SI == 0 Then
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; DS += __AHINCR
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; If DI == 0 Then
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; ES += __AHINCR
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;
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next:
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;;;;;;;;mov ax,cx
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;;;;;;;;dec ax
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mov ax,di
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not ax ; AX = 65535-DI
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mov dx,si
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not dx ; DX = 65535-SI
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sub ax,dx
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sbb bx,bx
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and ax,bx
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add ax,dx ; AX = MIN(AX,DX) = MIN(65535-SI,65535-DI)
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; problem: ax might have wrapped to zero
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test cbMem.hi,-1
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jnz plentytogo ; at least 64k still to copy
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dec cx ; this is ok, since high word is zero
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sub ax,cx
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sbb bx,bx
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and ax,bx
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add ax,cx ; AX = MIN(AX,CX)
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inc cx
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plentytogo:
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xor bx,bx
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add ax,1 ; AX = Num = MIN(count,65536-SI,65536-DI)
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; we must check the carry here!
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adc bx,0 ; BX could be 1 here, if CX==0 indicating
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; exactly 64k to copy
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xchg ax,cx
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sub ax,cx ; Count -= Num
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sbb cbMem.hi,bx
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shr bx,1
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rcr cx,1 ; if bx==1, then cx ends up 0x8000
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rep movsw
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adc cl,cl
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rep movsb ; move last byte, if necessary
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mov cx,ax ; put low word of count back in cx
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or ax,cbMem.hi
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jz done ; If Count == 0 Then BREAK
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or si,si ; if SI wraps, update DS
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jnz @f
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mov ax,ds
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add ax,__AHINCR
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mov ds,ax ; update DS if appropriate
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@@:
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or di,di ; if DI wraps, update ES
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jnz next
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mov ax,es
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add ax,__AHINCR
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mov es,ax ; update ES if appropriate
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jmp next
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;
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; Restore registers and return
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;
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done:
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empty_copy:
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mov dx,lpDst.sel ; return destination address
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mov ax,lpDst.off
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cEnd
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sEnd
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sEnd CodeSeg
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end
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