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https://github.com/microsoft/MS-DOS.git
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MS-DOS v2.0 Release
This commit is contained in:
Rich Turner
508
v2.0/source/BUF.ASM
Normal file
508
v2.0/source/BUF.ASM
Normal file
@@ -0,0 +1,508 @@
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;
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; buffer management for MSDOS
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;
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INCLUDE DOSSEG.ASM
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CODE SEGMENT BYTE PUBLIC 'CODE'
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ASSUME SS:DOSGROUP,CS:DOSGROUP
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.xlist
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.xcref
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INCLUDE DOSSYM.ASM
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INCLUDE DEVSYM.ASM
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.cref
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.list
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i_need BuffHead,DWORD
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i_need PreRead,WORD
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i_need LastBuffer,DWORD
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i_need CurBuf,DWORD
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i_need WPErr,BYTE
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SUBTTL SETVISIT,SKIPVISIT -- MANAGE BUFFER SCANS
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PAGE
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procedure SETVISIT,near
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ASSUME DS:NOTHING,ES:NOTHING
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; Inputs:
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; None
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; Function:
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; Set up a scan of I/O buffers
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; Outputs:
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; All visit flags = 0
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; NOTE: This pre-scan is needed because a hard disk error
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; may cause a scan to stop in the middle leaving some
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; visit flags set, and some not set.
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; DS:DI Points to [BUFFHEAD]
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; No other registers altered
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LDS DI,[BUFFHEAD]
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PUSH AX
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XOR AX,AX
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SETLOOP:
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MOV [DI.VISIT],AL
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LDS DI,[DI.NEXTBUF]
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CMP DI,-1
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JNZ SETLOOP
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LDS DI,[BUFFHEAD]
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POP AX
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return
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entry SKIPVISIT
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ASSUME DS:NOTHING,ES:NOTHING
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; Inputs:
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; DS:DI Points to a buffer
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; Function:
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; Skip visited buffers
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; Outputs:
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; DS:DI Points to next unvisited buffer
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; Zero is set if skip to LAST buffer
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; No other registers altered
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CMP DI,-1
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retz
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CMP [DI.VISIT],1
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retnz
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LDS DI,[DI.NEXTBUF]
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JMP SHORT SKIPVISIT
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return
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SetVisit ENDP
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SUBTTL SCANPLACE, PLACEBUF -- PUT A BUFFER BACK IN THE POOL
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PAGE
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procedure ScanPlace,near
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ASSUME DS:NOTHING,ES:NOTHING
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; Inputs:
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; Same as PLACEBUF
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; Function:
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; Save scan location and call PLACEBUF
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; Outputs:
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; DS:DI Points to saved scan location
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; SI destroyed, other registers unchanged
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PUSH ES
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LES SI,[DI.NEXTBUF] ; Save scan location
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CALL PLACEBUF
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PUSH ES
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POP DS ; Restore scan location
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MOV DI,SI
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POP ES
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return
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ScanPlace ENDP
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NRETJ: JMP SHORT NRET
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procedure PLACEBUF,NEAR
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ASSUME DS:NOTHING,ES:NOTHING
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; Input:
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; DS:DI points to buffer
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; Function:
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; Remove buffer from queue and re-insert it in proper place.
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; If buffer doesn't go at end, and isn't free, decrement
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; priorities.
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; NO registers altered
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;
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; DS:SI -- Curbuf, current buffer in list
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; ES:DI -- Buf, buffer passed as argument
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; BP:CX -- Pointsave, saved Buf.nextbuf
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; DX:BX -- Lastbuf, previous buffer in list
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; AL -- Inserted, Buf has been inserted
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; AH -- Removed, Buf has been removed
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IF IBM
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IF NOT IBM
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invoke save_world
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XOR AX,AX ; Inserted = Removed = FALSE
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LES CX,[DI.NEXTBUF]
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MOV BP,ES ; Pointsave = Buf.nextbuf
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MOV SI,DS
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MOV ES,SI ; Buf is ES:DI
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LDS SI,[BUFFHEAD] ; Curbuf = HEAD
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CALL POINTCOMP ; Buf == HEAD?
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JNZ TNEWHEAD
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CMP CX,-1 ; Buf is LAST?
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JZ NRETJ ; Only one buffer, nothing to do
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MOV WORD PTR [BUFFHEAD],CX
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MOV WORD PTR [BUFFHEAD+2],BP ; HEAD = Pointsave
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INC AH ; Removed = TRUE
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MOV DS,BP
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MOV SI,CX ; Curbuf = HEAD
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TNEWHEAD:
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MOV BL,ES:[DI.BUFPRI]
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CMP BL,[SI.BUFPRI]
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JGE BUFLOOP
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NEWHEAD: ; If Buf.pri < HEAD.pri
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MOV WORD PTR ES:[DI.NEXTBUF],SI
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MOV WORD PTR ES:[DI.NEXTBUF+2],DS ; Buf.nextbuf = HEAD
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MOV WORD PTR [BUFFHEAD],DI
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MOV WORD PTR [BUFFHEAD+2],ES ; HEAD = Buf
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INC AL ; Inserted = TRUE
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OR AH,AH
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JNZ NRET ; If Removed == TRUE
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BUFLOOP:
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PUSH DS
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PUSH SI
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LDS SI,[SI.NEXTBUF]
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CALL POINTCOMP
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POP SI
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POP DS
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JNZ TESTINS
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MOV WORD PTR [SI.NEXTBUF],CX ; If Curbuf.nextbuf == buf
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MOV WORD PTR [SI.NEXTBUF+2],BP ; Curbuf.nextbuf = Pointsave
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INC AH ; Removed = TRUE
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OR AL,AL
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JNZ SHUFFLE ; If Inserted == TRUE
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TESTINS:
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OR AL,AL
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JNZ LOOKBUF
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PUSH CX ; If NOT Inserted
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MOV CL,ES:[DI.BUFPRI]
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CMP CL,[SI.BUFPRI]
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POP CX
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JGE LOOKBUF
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PUSH DS ; If Buf.pri < Curbuf.pri
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MOV DS,DX
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MOV WORD PTR [BX.NEXTBUF],DI
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MOV WORD PTR [BX.NEXTBUF+2],ES ; Lastbuf.nextbuf = Buf
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POP DS
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MOV WORD PTR ES:[DI.NEXTBUF],SI
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MOV WORD PTR ES:[DI.NEXTBUF+2],DS ; Buf.nextbuf = Curbuf
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INC AL ; Inserted = TRUE
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OR AH,AH
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JNZ SHUFFLE ; If Removed == TRUE
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LOOKBUF:
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MOV BX,SI
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MOV DX,DS ; Lastbuf = Curbuf
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CMP WORD PTR [SI.NEXTBUF],-1
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JZ ISLAST
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LDS SI,[SI.NEXTBUF] ; Curbuf = Curbuf.nextbuf
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JMP SHORT BUFLOOP
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ISLAST: ; If Curbuf is LAST
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MOV WORD PTR [SI.NEXTBUF],DI
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MOV WORD PTR [SI.NEXTBUF+2],ES ; Curbuf.nextbuf = Buf
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MOV WORD PTR ES:[DI.NEXTBUF],-1
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MOV WORD PTR ES:[DI.NEXTBUF+2],-1 ; Buf is LAST
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NRET:
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invoke restore_world
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return
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SHUFFLE:
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LDS DI,[BUFFHEAD]
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DECLOOP:
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CMP [DI.BUFPRI],FREEPRI
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JZ NODEC
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DEC [DI.BUFPRI]
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NODEC:
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LDS DI,[DI.NEXTBUF]
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CMP DI,-1
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JNZ DECLOOP
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JMP SHORT NRET
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ENDIF
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ENDIF
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invoke save_world
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LES CX,[DI.NEXTBUF]
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CMP CX,-1 ; Buf is LAST?
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JZ NRET ; Buffer already last
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MOV BP,ES ; Pointsave = Buf.nextbuf
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PUSH DS
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POP ES ; Buf is ES:DI
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LDS SI,[BUFFHEAD] ; Curbuf = HEAD
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CALL POINTCOMP ; Buf == HEAD?
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JNZ BUFLOOP
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MOV WORD PTR [BUFFHEAD],CX
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MOV WORD PTR [BUFFHEAD+2],BP ; HEAD = Pointsave
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JMP SHORT LOOKEND
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BUFLOOP:
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PUSH DS
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PUSH SI
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LDS SI,[SI.NEXTBUF]
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CALL POINTCOMP
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JZ GOTTHEBUF
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POP AX
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POP AX
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JMP SHORT BUFLOOP
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GOTTHEBUF:
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POP SI
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POP DS
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MOV WORD PTR [SI.NEXTBUF],CX ; If Curbuf.nextbuf == buf
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MOV WORD PTR [SI.NEXTBUF+2],BP ; Curbuf.nextbuf = Pointsave
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LOOKEND:
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PUSH DS
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PUSH SI
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LDS SI,[SI.NEXTBUF]
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CMP SI,-1
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JZ GOTHEEND
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POP AX
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POP AX
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JMP SHORT LOOKEND
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GOTHEEND:
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POP SI
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POP DS
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MOV WORD PTR [SI.NEXTBUF],DI
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MOV WORD PTR [SI.NEXTBUF+2],ES ; Curbuf.nextbuf = Buf
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MOV WORD PTR ES:[DI.NEXTBUF],-1
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MOV WORD PTR ES:[DI.NEXTBUF+2],-1 ; Buf is LAST
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NRET:
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invoke restore_world
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return
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PLACEBUF ENDP
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procedure PLACEHEAD,NEAR
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ASSUME DS:NOTHING,ES:NOTHING
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; SAME AS PLACEBUF except places buffer at head
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invoke save_world
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PUSH DS
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POP ES
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LDS SI,[BUFFHEAD]
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MOV WORD PTR [BUFFHEAD],DI
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MOV WORD PTR [BUFFHEAD+2],ES
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MOV WORD PTR ES:[DI.NEXTBUF],SI
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MOV WORD PTR ES:[DI.NEXTBUF+2],DS
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LOOKEND2:
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PUSH DS
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PUSH SI
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LDS SI,[SI.NEXTBUF]
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CALL POINTCOMP
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JZ GOTHEEND2
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POP AX
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POP AX
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JMP SHORT LOOKEND2
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GOTHEEND2:
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POP SI
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POP DS
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MOV WORD PTR [SI.NEXTBUF],-1
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MOV WORD PTR [SI.NEXTBUF+2],-1 ; Buf is LAST
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JMP SHORT NRET
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PLACEHEAD ENDP
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SUBTTL POINTCOMP -- 20 BIT POINTER COMPARE
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PAGE
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procedure PointComp,NEAR
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ASSUME DS:NOTHING,ES:NOTHING
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; Compare DS:SI to ES:DI (or DS:DI to ES:SI) for equality
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; DO NOT USE FOR < or >
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; No Registers altered
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CMP SI,DI
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retnz
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PUSH CX
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PUSH DX
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MOV CX,DS
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MOV DX,ES
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CMP CX,DX
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POP DX
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POP CX
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return
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PointComp ENDP
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SUBTTL GETBUFFR -- GET A SECTOR INTO A BUFFER
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PAGE
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procedure GETBUFFR,NEAR
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ASSUME DS:DOSGROUP,ES:NOTHING
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; Input:
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; AH = Priority buffer is to have
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; AL = 0 means sector must be pre-read
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; ELSE no pre-read
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; DX = Desired physical sector number
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; ES:BP = Pointer to drive parameters
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; Function:
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; Get the specified sector into one of the I/O buffers
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; And shuffle the queue
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; Output:
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; [CURBUF] Points to the Buffer for the sector
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; DX,ES:BP unchanged, all other registers destroyed
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XOR SI,SI
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entry GETBUFFRB
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MOV [PREREAD],AX
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MOV AL,ES:[BP.dpb_drive]
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LDS DI,[LASTBUFFER]
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ASSUME DS:NOTHING
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CMP DI,-1 ; Recency pointer valid?
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JZ SKBUF ; No
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CMP DX,[DI.BUFSECNO]
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JNZ SKBUF ; Wrong sector
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CMP AL,[DI.BUFDRV]
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JNZ SKBUF ; Wrong Drive
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JMP SHORT JUSTBUF ; Just asked for same buffer
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SKBUF:
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LDS DI,[BUFFHEAD]
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NXTBFF:
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CMP DX,[DI.BUFSECNO]
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JNZ BUMP
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CMP AL,[DI.BUFDRV]
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JNZ BUMP
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JMP SHORT SETINF
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BUMP:
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LDS DI,[DI.NEXTBUF]
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CMP DI,-1
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JNZ NXTBFF
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LDS DI,[BUFFHEAD]
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PUSH SI
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PUSH DX
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PUSH BP
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PUSH ES
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CALL BUFWRITE ; Write out the dirty buffer
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POP ES
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POP BP
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POP DX
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POP SI
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RDSEC: ; Read in the new sector
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TEST BYTE PTR [PREREAD],-1
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JNZ SETBUF
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LEA BX,[DI.BufInSiz] ; Point at buffer
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MOV CX,1
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PUSH SI
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PUSH DI
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PUSH DX
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OR SI,SI
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JZ NORMSEC
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invoke FATSECRD
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JMP SHORT GOTTHESEC ; Buffer is marked free if read barfs
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NORMSEC:
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invoke DREAD ; Buffer is marked free if read barfs
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GOTTHESEC:
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POP DX
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POP DI
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POP SI
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SETBUF:
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MOV [DI.BUFSECNO],DX
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MOV WORD PTR [DI.BUFDRVDP],BP
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MOV WORD PTR [DI.BUFDRVDP+2],ES
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XOR AH,AH
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MOV AL,ES:[BP.dpb_drive]
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MOV WORD PTR [DI.BUFDRV],AX
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SETINF:
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MOV AX,1 ; Default to not a FAT sector
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OR SI,SI
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JZ SETSTUFFOK
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MOV AL,ES:[BP.dpb_FAT_count]
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MOV AH,ES:[BP.dpb_FAT_size]
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SETSTUFFOK:
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MOV WORD PTR [DI.BUFWRTCNT],AX
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CALL PLACEBUF
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JUSTBUF:
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MOV WORD PTR [CURBUF+2],DS
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MOV WORD PTR [LASTBUFFER+2],DS
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PUSH SS
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POP DS
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ASSUME DS:DOSGROUP
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MOV WORD PTR [CURBUF],DI
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MOV WORD PTR [LASTBUFFER],DI
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return
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GETBUFFR ENDP
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SUBTTL FLUSHBUF -- WRITE OUT DIRTY BUFFERS
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PAGE
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procedure FlushBuf,NEAR
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ASSUME DS:DOSGROUP,ES:NOTHING
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; Input:
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; DS = DOSGROUP
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; AL = Physical unit number
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; = -1 for all units
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; Function:
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; Write out all dirty buffers for unit, and flag them as clean
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; DS Preserved, all others destroyed (ES too)
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LDS DI,[BUFFHEAD]
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ASSUME DS:NOTHING
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MOV AH,-1
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NXTBUFF:
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CMP [DI.BUFDRV],AH
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JZ SKIPBFF ; Skip free buffers
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CMP AH,AL
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JZ DOBUFFER ; Do all dirty buffers
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CMP AL,[DI.BUFDRV]
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JNZ SKIPBFF ; Buffer not for this unit
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DOBUFFER:
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CMP BYTE PTR [DI.BUFDIRTY],0
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JZ SKIPBFF ; Buffer not dirty
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PUSH AX
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PUSH WORD PTR [DI.BUFDRV]
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CALL BUFWRITE
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POP AX
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XOR AH,AH ; Buffer is clean
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CMP AL,BYTE PTR [WPERR]
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JNZ NOZAP
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MOV AL,0FFH ; Invalidate buffer, it is inconsistent
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NOZAP:
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MOV WORD PTR [DI.BUFDRV],AX
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POP AX ; Search info
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SKIPBFF:
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LDS DI,[DI.NEXTBUF]
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CMP DI,-1
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JNZ NXTBUFF
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PUSH SS
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POP DS
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return
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FlushBuf ENDP
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SUBTTL BUFWRITE -- WRITE OUT A BUFFER IF DIRTY
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PAGE
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procedure BufWrite,NEAR
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ASSUME DS:NOTHING,ES:NOTHING
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; Input:
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; DS:DI Points to the buffer
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; Function:
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; Write out all the buffer if dirty.
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; Output:
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; Buffer marked free
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; DS:DI Preserved, ALL others destroyed (ES too)
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MOV AX,00FFH
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XCHG AX,WORD PTR [DI.BUFDRV] ; Free, in case write barfs
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CMP AL,0FFH
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retz ; Buffer is free.
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OR AH,AH
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retz ; Buffer is clean.
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CMP AL,BYTE PTR [WPERR]
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retz ; If in WP error zap buffer
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LES BP,[DI.BUFDRVDP]
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LEA BX,[DI.BufInSiz] ; Point at buffer
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MOV DX,[DI.BUFSECNO]
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MOV CX,WORD PTR [DI.BUFWRTCNT]
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MOV AL,CH ; [DI.BUFWRTINC]
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XOR CH,CH
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MOV AH,CH
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PUSH DI
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WRTAGAIN:
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PUSH CX
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PUSH AX
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MOV CX,1
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PUSH BX
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PUSH DX
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invoke DWRITE ; Write out the dirty buffer
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POP DX
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POP BX
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POP AX
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POP CX
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ADD DX,AX
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LOOP WRTAGAIN
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POP DI
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return
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BufWrite ENDP
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do_ext
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CODE ENDS
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||||
END
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Reference in New Issue
Block a user