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Assembly Source File | 1988-10-11 | 54.2 KB | 1,036 lines

;========================================================================== ; DCACHE.COM - A fixed disk cache for the IBM Personal Computer. ; PC Magazine, Vol 7 # 17 ;-------------------------------------------------------------------------- CODE SEGMENT PARA PUBLIC 'CODE' ASSUME CS:CODE ORG 2CH ENV_SEG DW ? ;Segment of the environment block ORG 80H TAIL_LENGTH DB ? ;Length of the command tail ORG 100H ENTRY: JMP MAIN_ENTRY ;-------------------------------------------------------------------------- ; Data Area ;-------------------------------------------------------------------------- PROGRAM DB 'DCACHE 1.0 (c) 1988 Ziff Communications Co.',13,10 DB 'PC Magazine ',254,' Douglas Boling',13,10,'$',26 ENABLED DB 1 ;0 = cache disabled, 1 = enabled EMS_FLAG DB 0 ;use EMS ram flag, 1 = use EMS EMS_HANDLE DW 0 ;handle for EMS memory. ADDR_MASK DW 001EH ;Default mask set for 64K cache SIZE_MASK DW 0 EMS_MASK DW 0 ;used to sel. the proper EMS page DISK_NUM DB 80H ;number of fixed disk to cache PAGE_SIZE DB 8 ;size of cache page MAX_HEAD DW ? ;maximum value of head parameter MAX_SECTOR DW ? ;maximum value of sector MAX_SEGMENT DW ? ;last segment of data cache DOSBOFFSET DW ? ;offset of dos data buffer DOSBSEGMENT DW ? ;sector of dos data buffer NUM_OF_SEC DB ? ;number of sectors requested DISK_FUNCT DB ? ;function requested SECTOR_NUM DW ? ;sector parameter from dos call HEAD_NUM DB ? ;head parameter CYLINDER_NUM DW ? ;cylinder parameter SEGMENT_PTR DW 0 ;pointers into the cache PAGE_PTR DW 0 LOG_SEC_HIGH DW 0 ;Logical sector number of disk LOG_SEC_LOW DW 0 ; request. LAST_BAD_PAGE DW -1 ;stores the last page that ;contained an error LOOKUPTABLE DW OFFSET DATA_START ;offset of lookup table CACHE_SEGMENT DW 0 ;segment of cache data OLD_DISK_INT LABEL DWORD ;old bios interrupt 13h vector OLD_INT13H DW 2 DUP (?) ;----------------------------------------------------------------------------- ; This routine intercepts the bios disk calls. ; Entry: ah - disk function (All other registers specific to disk read.) ; al - number of sectors es:bx - pointer to data buffer ; ch - Cylinder number dh - Head number ; cl - 7,6 Cyl. high. 5-0 sector number dl - drive number ;----------------------------------------------------------------------------- DISK_INT PROC FAR ASSUME CS:CODE,DS:NOTHING,ES:NOTHING CMP CS:ENABLED,0 ;See if cache enabled JE SKIP_CACHE CMP DL,CS:DISK_NUM ;See if the correct disk JNE SKIP_CACHE STI ;Allow interrupts CMP AH,2 ;If any other function besides JE CACHE_IT ; read or write, reset cache. CMP AH,3 JE CACHE_IT1 CMP AH,1 ;If just checking the last status JE SKIP_CACHE ; skip cache, but don't reset. RESET_CMD: PUSH ES ;If the command is not a simple PUSH CS ; read, write, or status, assume POP ES ; the worst and clear the lookup ASSUME ES:CODE ; table. CALL RESET_CACHE POP ES ASSUME ES:NOTHING SKIP_CACHE: JMP CS:OLD_DISK_INT ;jmp to bios disk routine. ;-------------------------------------------------------------------------- ;Compute the logical sector number from the cylinder, head, and sector. ;-------------------------------------------------------------------------- CACHE_IT: CMP AL,CS:PAGE_SIZE ;For disk read, cache reads of JA SKIP_CACHE ; a page or less. CACHE_IT1: PUSH DS ;save registers PUSH DI PUSH SI PUSHF PUSH AX PUSH BX PUSH CX PUSH DX PUSH CS ;set ds to code segment POP DS ASSUME DS:CODE ;-------------------------------------------------------------------------- ;Store calling parameters. ;-------------------------------------------------------------------------- MOV DOSBOFFSET,BX ;save dos pointer to its data MOV DOSBSEGMENT,ES ; buffer. MOV BX,CX ;copy cx AND BX,003FH ;strip all but the sector number MOV SECTOR_NUM,BX ;save sector number MOV HEAD_NUM,DH ;save head number MOV NUM_OF_SEC,AL ;save the number of sectors needed MOV DISK_FUNCT,AH ;save function called. ;-------------------------------------------------------------------------- ;Compute logical sector number from the cylinder, head, and sector parameters. ;-------------------------------------------------------------------------- XCHG CL,CH ;create full 10 bit cylinder num. ROL CH,1 ; the top 2 bits are in ch bits ROL CH,1 ; 7 and 6. roll them into bits AND CH,03H ; 1 and 2. MOV CYLINDER_NUM,CX ;save the cylinder number MOV AX,CX ;copy cylinder number for multiply MOV BL,DH ;get head number out of dx MUL MAX_HEAD ;multiply cylinder to make room XOR BH,BH ;clear high byte of head value ADD AX,BX ;add in head. MUL MAX_SECTOR ;multiply by max sector value ADD AX,SECTOR_NUM ;add sector number ADC DX,0 ;propigate carry. MOV LOG_SEC_HIGH,DX ;save logical sector number MOV LOG_SEC_LOW,AX ;-------------------------------------------------------------------------- ;Store values needed later. ;-------------------------------------------------------------------------- MOV BH,AL SHL BH,1 AND BX,3E00H MOV PAGE_PTR,BX ;save page index AND BH,30H MOV SI,BX ;save page index for cache load ;-------------------------------------------------------------------------- ;Point the segment register to the proper DOS memory block ;-------------------------------------------------------------------------- MOV BX,AX ;copy logical sector low MOV CL,5 SHL BX,CL ;Convert logical sector number to AND BX,SIZE_MASK ; cache page index ADD BX,CACHE_SEGMENT MOV SEGMENT_PTR,BX ;save segment index MOV BX,AX ;copy logical sector number MOV DI,LOOKUPTABLE ;use di to point to lookup table ;-------------------------------------------------------------------------- ;Check for a read or a write ;-------------------------------------------------------------------------- CMP DISK_FUNCT,2 JNE DISK_WRITE JMP DISK_READ ;-------------------------------------------------------------------------- ;Process bios write calls. ;-------------------------------------------------------------------------- DISK_WRITE: MOV CL,AL ;See if the write crosses a page AND CL,07H ; boundry. If > 8, it does. MOV CH,NUM_OF_SEC ADD CL,CH CMP CL,PAGE_SIZE ;If the write crosses a page JA WRITE_UPDATE_SKP ; boundry, skip the update and CMP EMS_FLAG,0 ; just purge the cache. JE WRITE_SKP_EMS CALL EMS_SETUP ;access the EMS page bx=logsec_low WRITE_SKP_EMS: PUSH AX CALL CHECK_HIT ;Check to see if the data is in POP AX ; the cache. JNE EXIT_AND_RESTORE ;If miss, skip all this stuff ;-------------------------------------------------------------------------- ;Since the data is in the cache, update just the stuff to be written ;-------------------------------------------------------------------------- XOR CL,CL MOV DI,PAGE_PTR ;Load the pointers for the data MOV SI,DOSBOFFSET ; move. ch already contains the MOV ES,SEGMENT_PTR ; number of sectors to move. cx MOV DS,DOSBSEGMENT ; then contains the number of ASSUME DS:NOTHING,ES:NOTHING ; words to move. CLD REP MOVSW ;Copy the data to be written into PUSH CS ; the cache. POP DS ASSUME DS:CODE JMP SHORT EXIT_AND_RESTORE ;-------------------------------------------------------------------------- ;If the write crosses a page boundry, just delete the entry from the table. ;-------------------------------------------------------------------------- WRITE_UPDATE_SKP: MOV SI,AX ;Save logical sector low logical MOV CL,PAGE_SIZE ; sector high will be fine in dx. DEC CH DISK_WRITE1: CMP CH,CL ;If the number of sectors is less JA DISK_WRITE2 ; than the page size, decriment MOV CL,CH ; by the number of sectors DISK_WRITE2: PUSH CX CALL CHECK_HIT ;Check to see if the sector POP CX JNE DISK_WRITE3 ;is in table. Purge the tag if MOV WORD PTR [DI][BX],0FFFFH ;this is a hit. DISK_WRITE3: PUSH SI ;Save copy of logical sector num SUB CH,CL MOV BL,CL ;Subtract the page size from the XOR BH,BH ; number of sectors written. Add ADD SI,BX ; to the logical sector number. ADC DL,0 MOV AX,SI ;Move logical sector low to ax. POP BX ;Get sector before add for compare XOR BX,AX ;If there is no difference in the TEST BL,08H ; logical page after the inc then JNZ DISK_WRITE1 ; exit the loop. ;-------------------------------------------------------------------------- ;restore the registers for the bios call. ;-------------------------------------------------------------------------- EXIT_TO_BIOS: POP DX ;jump to the bios interrupt as if POP CX ; we were not here. POP BX POP AX POPF MOV ES,DOSBSEGMENT POP SI POP DI POP DS JMP CS:OLD_DISK_INT ;-------------------------------------------------------------------------- ;Exit to bios and restore EMS if necessary ;-------------------------------------------------------------------------- EXIT_AND_RESTORE: CMP EMS_FLAG,0 JE EXIT_TO_BIOS MOV AH,48H ;Restore EMS configuration MOV DX,EMS_HANDLE INT 67H OR AH,AH JE EXIT_TO_BIOS INT_EMS_ERR: MOV ENABLED,0 ;EMS error, assume the worst and JMP SHORT EXIT_TO_BIOS ; disable the cache. ;-------------------------------------------------------------------------- ;Process bios read calls. ;-------------------------------------------------------------------------- DISK_READ: ASSUME DS:CODE ;If using Expanded memory, get the needed segments. CMP EMS_FLAG,0 JE INT_DOS_MEM CALL EMS_SETUP INT_DOS_MEM: ;-------------------------------------------------------------------------- ;Convert logical sector number to an index into the lookup table. ;-------------------------------------------------------------------------- XOR CL,CL ;clear sector counter CALL CHECK_HIT ;see if we have a hit CMP AX,LAST_BAD_PAGE ;If this page has a bad sector JE EXIT_AND_RESTORE ; don't fetch it. MOV WORD PTR [DI][BX],AX ;update the look up table. ;-------------------------------------------------------------------------- ;if we need 2 pages, check to see if the other page is in the cache ;-------------------------------------------------------------------------- MOV AX,LOG_SEC_LOW ;Add the number of sectors needed MOV CH,AL ; to the displacment in the page AND CH,07H ; if > 8, we need 2 pages. ADD CH,NUM_OF_SEC CMP CH,PAGE_SIZE JLE END_OF_CHK ;we only need 1 page CMP SI,03000H JNE CHK_2ND_PAGE MOV DX,SEGMENT_PTR ;check to see if we are at the CMP DX,MAX_SEGMENT ; very top of the cache and we JB CHK_2ND_PAGE MOV [DI][BX],0FFFFH ;clear lookup table JMP SHORT EXIT_AND_RESTORE ;skip cache. ;-------------------------------------------------------------------------- ;adjust the index into the lookup table to check for the second page. ;-------------------------------------------------------------------------- CHK_2ND_PAGE: MOV DX,LOG_SEC_HIGH ;we need 2 pages, check to see if XOR BH,BH ; the other page is in the cache. MOV BL,NUM_OF_SEC ADD AX,BX ;Do this by adding the number of ADC DL,0 ; sectors needed to the starting CALL CHECK_HIT ; logical sector number. JE END_OF_CHK ;skip next if second page hit. MOV WORD PTR [DI][BX],AX ;update the look up table. MOV AL,PAGE_SIZE CMP CL,AL ;If we need only the second page, JNE END_OF_CHK ; adjust the starting pointers ADD SI,1000H ; into the cache. XOR AH,AH ADD LOG_SEC_LOW,AX ADC LOG_SEC_HIGH,0 END_OF_CHK: ;-------------------------------------------------------------------------- ;Now that we have checked for the data in the cahe, jump to the right routine ;-------------------------------------------------------------------------- CMP CL,0 ;check the number of sectors to JE CACHE_HIT ; read from the disk. ;-------------------------------------------------------------------------- ;The request is a cache miss. Load the data needed from the disk to the cache. ;-------------------------------------------------------------------------- CACHE_MISS: XOR CH,CH MOV DI,CX ;save the number of sectors needed ;-------------------------------------------------------------------------- ;Use the logical sector number to compute the new calling parameters. ;-------------------------------------------------------------------------- XOR CX,CX ;clear a place for the sector num MOV DX,LOG_SEC_HIGH ;put the logical sector number MOV AX,LOG_SEC_LOW ; into dx,ax AND AX,0FFF8H ;clear off the odd sector JNE SET_REGS ;if the resulting logical sector OR DX,DX ; number is 0, modify the calling JNE SET_REGS ; parameters to allow for the INC AX ; sectors starting at 1. ADD SI,200H ;si holds the cache target address DEC DI ;di holds the number of sectors SET_REGS: ; to fetch. DIV MAX_SECTOR OR CX,DX ;save the remainder (sector num) JNE SET_REGS1 ;Since the sector number can not MOV CX,MAX_SECTOR ; be zero, check for this and DEC AX ; correct if necessary. SET_REGS1: XOR DX,DX ;remove the remainder DIV MAX_HEAD ;-------------------------------------------------------------------------- ;put cylinder and sector parameters into their proper registers. ;-------------------------------------------------------------------------- MOV DH,DL ;move head to proper register. XCHG AL,AH ;Put the cylinder number into the ROR AL,1 ; strange, but required registers ROR AL,1 OR CX,AX ;-------------------------------------------------------------------------- ;Compute data buffer inside cache. ;-------------------------------------------------------------------------- MOV BX,SI ;Point the data buffer for the MOV ES,SEGMENT_PTR ; call to the proper cache page. ASSUME ES:NOTHING ;-------------------------------------------------------------------------- ;complete the parameters for the bios call. ;-------------------------------------------------------------------------- MOV AX,DI ;get the number of sectors to read MOV AH,02H ;read data from disk MOV DL,DISK_NUM ;access the correct disk ;-------------------------------------------------------------------------- ;Set up parameters and call real bios int 13h. ;-------------------------------------------------------------------------- PUSH AX PUSHF CALL OLD_DISK_INT POP SI JC BIOS_ERROR ;if an error ocurred, deal with it ;-------------------------------------------------------------------------- ;Cache hit. Transfer the data from the cache to the dos buffer. ;-------------------------------------------------------------------------- CACHE_HIT: MOV DI,DOSBOFFSET ;Load es:di with the dos data MOV ES,DOSBSEGMENT ; buffer. ASSUME ES:NOTHING MOV CH,NUM_OF_SEC ;Put number of words to transfer XOR CL,CL ; into cx. MOV SI,PAGE_PTR ;Load ds:si with the location of MOV DS,SEGMENT_PTR ; the data in the cache. ASSUME DS:NOTHING CLD REP MOVSW ;Transfer the data from the cache PUSH CS POP DS ASSUME DS:CODE EXIT_TO_CALLER: ; to the caller of int 13h ;-------------------------------------------------------------------------- ;Restore EMS configuration if necessary. ;-------------------------------------------------------------------------- CMP EMS_FLAG,0 ;Check to see if we are using JE CALLER_EXIT_SKIP ; ems memory. MOV AH,48H MOV DX,EMS_HANDLE ;If so, restore the mapping INT 67H ; context used before this OR AH,AH ; interrupt. JE CALLER_EXIT_SKIP JMP INT_EMS_ERR CALLER_EXIT_SKIP: POP DX POP CX POP BX POP AX POPF XOR AX,AX ;Clear ax to indicate 0 return POP SI ; code. POP DI POP DS CLC ;Clear carry to indicate no error. RET 2 ;Return but keep current flags ;----------------------------------------------------------------------------- ;Error routine ;----------------------------------------------------------------------------- BIOS_ERROR: ASSUME DS:CODE MOV AX,LOG_SEC_LOW ;Get logical sector, convert it MOV DX,LOG_SEC_HIGH ; into an index into the MOV DI,LOOKUPTABLE ; lookup table, then erase the CALL CHECK_HIT ; tag. MOV WORD PTR [DI][BX],0FFFFH MOV CX,SI ;See if we were reading 2 CMP CL,PAGE_SIZE ; pages. If so, clear next JLE BIOS_ERROR1 ; entry in the lookup table. ADD BX,2 MOV WORD PTR [DI][BX],0FFFFH BIOS_ERROR1: MOV LAST_BAD_PAGE,AX XOR AX,AX MOV DL,DISK_NUM ;Reset disk system using PUSHF ; bios int 13 function 0. CALL OLD_DISK_INT JMP EXIT_AND_RESTORE DISK_INT ENDP ;----------------------------------------------------------------------------- ;EMS Setup This routine saves the current state of the EMS driver, then ; loads in the proper EMS page needed for the cache. ;Entry: bx - low word of logical sector number ;----------------------------------------------------------------------------- EMS_SETUP PROC NEAR ASSUME DS:CODE PUSH AX PUSH DX MOV CL,5 SHR BX,CL ;Convert logical sector num to AND BX,EMS_MASK ; a physical EMS page number. ;-------------------------------------------------------------------------- ;Save current state of EMS driver ;-------------------------------------------------------------------------- MOV AH,47H ;Save state function MOV DX,EMS_HANDLE INT 67H ;call EMS driver OR AH,AH ;check for error JNE EMS_SETUP_ERR ;-------------------------------------------------------------------------- ;Get the proper EMS pages from the EMS driver. ;-------------------------------------------------------------------------- MOV AX,4400H ;map EMS memory to cache segment INT 67H OR AH,AH ;check for EMS error JNE EMS_SETUP_ERR POP DX POP AX RET EMS_SETUP_ERR: ADD SP,6 ;clean up stack JMP INT_EMS_ERR EMS_SETUP ENDP ;----------------------------------------------------------------------------- ;Check hit. This routine checks the lookup table for a match. ;Entry: dl,ax logical sector number. Exit: ZF set = hit, ZF clear, miss ; cl = number of sectors to fetch cl = updated number of sectors ; di = base of lookup table ;----------------------------------------------------------------------------- CHECK_HIT PROC NEAR ASSUME DS:CODE AND AX,0FFF8H ;remove the page index. OR AX,DX ;add in the top 3 bits MOV BX,AX ;copy the log sec num to bx to SHR BX,1 ; create the table index. SHR BX,1 AND BX,ADDR_MASK ;Use the addr mask to limit the CMP AX,WORD PTR [DI][BX] ; size of the lookup table JE CHECK_HIT1 ;Check for a hit. ADD CL,PAGE_SIZE ;cache miss, grab a page of sectors CHECK_HIT1: RET CHECK_HIT ENDP ;----------------------------------------------------------------------------- ;Reset Cache. Routine clears the cache look up table. ;Entry ds - segment of the lookup table, and the lookup table offset ;----------------------------------------------------------------------------- RESET_CACHE PROC NEAR ASSUME CS:CODE,DS:NOTHING,ES:NOTHING PUSH DI PUSH CX PUSH AX MOV AX,0FFFFH MOV DI,ES:LOOKUPTABLE ;point di to the lookup table MOV CX,ES:ADDR_MASK ;compute size of the lookup table SHR CX,1 INC CX REP STOSW ;write ffff to each entry in the POP AX ; lookup table. POP CX POP DI RET RESET_CACHE ENDP ;-------------------------------------------------------------------------- ;Safe place to clear lookup table. ;-------------------------------------------------------------------------- INSTALL1: ASSUME DS:CODE ;DS points to code segment PUSH CS POP ES ;point es to lookup table segment ASSUME ES:NOTHING CALL RESET_CACHE ;Clear lookup table POP CX ;get state of enable flag MOV ENABLED,CL ;Terminate and stay resident INT 21H ; with 0 return code. ;------------------------------------------------------------------------- ;Data area not needed by resident routine. ;------------------------------------------------------------------------- EVEN ;start lookup table on even byte DATA_START = $ ;========================================================================= ;Non-resident code. ;------------------------------------------------------------------------- LOOKUP_SIZE DW 0 ;size of the lookup table TERM_MEM DW 0 ;amount of memory needed at end. ALRDY_IN_MEM DB 0 ;flag indicating cache installed. OTHER_SEG DW 0 ;segment of installed copy EMS_HEADER DB 'EMMXXXX0' ;Header of EMS driver. HELP0 DB 13,10,'Options:',13,10 DB '/OFF - Disable Cache',13,10 DB '/ON - Enable Cache',13,10 DB '/U - Uninstall Cache',13,10,'$' HELP01 DB '/Mx - Set Cache Size To x KB',13,10 DB '/E - Use EMS',13,10 DB '/Hx - Cache Physical Disk x',13,10 DB 'Defaults: /M64 /H0 /ON',13,10,'$' HELP1 DB 'Invalid Cache Size$' HELP2 DB 'Already Installed$' HELP3 DB 'Invalid Command$' HELP6 DB 'Hard Disk Too Large$' HELP7 DB 'No EMS Memory$' HELP8 DB 'EMS Driver Error$' HELP9 DB 'Invalid Disk$' HELP10 DB 'Cannot Uninstall$' MSG1 DB 'Cache Installed',13,10,'$' MSG2 DB 'Not Enough Memory',13,10,'$' COMMANDS DB 'oumhe' ;Letters corrsponding to the COMMANDS_END = $ ; command line switches. MEM_SIZE_TBL DB '16326412255110204081' ;Numbers corresponding to the MEM_SIZE_TBL_END = $ ; allowable cache sizes. JUMPTABLE: DW OFFSET CACHE_ON_OFF DW OFFSET UNINSTALL DW OFFSET CACHE_SIZE DW OFFSET DISK_SELECT DW OFFSET EXPANDED_MEM ;----------------------------------------------------------------------------- ;Main. This routine performs the instalation, and modification of the cache. ;----------------------------------------------------------------------------- MAIN PROC ASSUME CS:CODE,DS:CODE,ES:CODE,SS:CODE MAIN_ENTRY: ;----------------------------------------------------------------------------- ;display program header ;----------------------------------------------------------------------------- MOV DX,OFFSET PROGRAM MOV AH,9 INT 21H ;----------------------------------------------------------------------------- ;Deallocate environment block ;----------------------------------------------------------------------------- PUSH ES MOV ES,ENV_SEG ;Get the segment from the PSP ASSUME ES:NOTHING MOV AH,49H ;Call dos release memory function. INT 21H POP ES ASSUME ES:CODE ;----------------------------------------------------------------------------- ;check for other copies of this program in memory. ;----------------------------------------------------------------------------- FIND_COPIES: XOR BX,BX ;Start search a segment 0 MOV WORD PTR [ENTRY],BX MOV AX,CS ;Get current segment FIND_LOOP: INC BX ;Check next segment MOV ES,BX ;Use es as segment pointer ASSUME ES:NOTHING CMP AX,BX ;Did we find ourselves? JE NO_COPIES ;Yes, only 1 copy in memory MOV SI,OFFSET ENTRY ;SI is the offset pointer MOV DI,SI ;Look the same place in both segs MOV CX,16 ;Check 16 bytes CLD ;Incriment pointers during compare REPE CMPSB ;Compare bytes JNE FIND_LOOP ;If no compare, check another seg INC ALRDY_IN_MEM ;Set already installed flag ;-------------------------------------------------------------------------- ;Check for other parameters on the command line. ;-------------------------------------------------------------------------- NO_COPIES: MOV OTHER_SEG,ES ;Save the segment of the copy PUSH CS POP ES ASSUME ES:CODE MOV DI,OFFSET TAIL_LENGTH ;Use di to point to command line MOV AX,1234H ;Set ax to 1234 to indicate if a FIND_COMMAND: ; command was ever found. INC DI DEC TAIL_LENGTH ;If we are at the end of the JL FIND_COMMAND_DONE ; command line, exit. CMP BYTE PTR [DI],'?' JE DISP_HELP CMP BYTE PTR [DI],'/' ;if / found a command may JNE FIND_COMMAND ; follow. ;-------------------------------------------------------------------------- ;Figure out what the command is, then process it if possible. ;-------------------------------------------------------------------------- DECODE_COMMAND: MOV SI,OFFSET COMMANDS ;Use si to point to the possible XOR BX,BX ; command letters. MOV AL,1[DI] ;Get command from tail OR AL,20H ;Convert uppercase to lower DECODE_LOOP: CMP AL,[SI] ;Search the list of allowable JE COMMAND_FOUND ; commands. INC BX ;If the letters don't match, INC SI ; inc the pointers to the cmd CMP SI,OFFSET COMMANDS_END ;If the command was not found, JBE DECODE_LOOP ; display error message. ILLEGAL_COMMAND: MOV DX,OFFSET HELP3 ;Command unrecognised. JMP SHORT HELP_ROUTINE COMMAND_FOUND: CMP BL,1 ;Allow only on, off, and remove JLE COMMAND_FOUND1 ; if cache already installed. CMP ALRDY_IN_MEM,0 JNE DISP_HELP2 COMMAND_FOUND1: SAL BX,1 ;Convert bx into an index into ADD BX,OFFSET JUMPTABLE ; the jump table. CALL [BX] JC HELP_ROUTINE ;If the carry flag is set on JMP SHORT FIND_COMMAND ; return, display error message. FIND_COMMAND_DONE: CMP ALRDY_IN_MEM,0 ;If not installed, install. JE INSTALL_CACHE CMP AX,1234H ;Were any commands processed? JE DISP_HELP2 ;No, print already installed msg TERMINATE: MOV AX,4C00H ;Terminate with 0 return code. INT 21H ;----------------------------------------------------------------------------- ;Print help lines. ;----------------------------------------------------------------------------- DISP_HELP2: MOV DX,OFFSET HELP2 ;dcache already installed JMP SHORT HELP_ROUTINE DISP_HELP6: MOV DX,OFFSET HELP6 ;Disk too large HELP_ROUTINE: PUSH DX ;Save offset to message MOV AH,2 ;Output a carrage return MOV DL,10 ; to put a space between INT 21H ; the messages. POP DX ;Get back offset. MOV AH,9 ;DOS print string routine INT 21H DISP_HELP: MOV DX,OFFSET HELP0 ;Display possible commands MOV AH,9 INT 21H CMP ALRDY_IN_MEM,1 ;Check already installed flag JE RETURN_WITH_1 MOV DX,OFFSET HELP01 ;If not already installed, print MOV AH,9 ; full list of allowable INT 21H ; command line switches. RETURN_WITH_1: MOV AX,4C01H ;Terminate with 1 return code. INT 21H ;----------------------------------------------------------------------------- ;Install routine. Compute disk parameters, reserve ems memory if needed, ; compute lookup table size, then jump to install1 routine. ;----------------------------------------------------------------------------- INSTALL_CACHE: MOV AH,08H ;Read drive parameters MOV DL,DISK_NUM INT 13H JNC GOOD_DRIVE ;Check to insure that a valid MOV DX,OFFSET HELP9 ; disk has been selected. JMP SHORT HELP_ROUTINE GOOD_DRIVE: MOV DL,DH XOR DH,DH INC DX MOV MAX_HEAD,DX ;save maximum head value MOV AX,CX AND CX,003FH MOV MAX_SECTOR,CX ;save maximum sector value XCHG AH,AL ;Compute the largest logical ROL AH,1 ; sector value. If the value is ROL AH,1 ; larger than 19 bits, display AND AX,03FFH ; error message and exit. MUL MAX_HEAD ADD AX,MAX_HEAD MUL MAX_SECTOR ADD AX,MAX_SECTOR ADC DX,0 CMP DL,8 JAE DISP_HELP6 ;----------------------------------------------------------------------------- ;Allocate memory for the cache. ;----------------------------------------------------------------------------- MOV AX,ADDR_MASK ;Compute amount of memory needed INC AX ; for the cache. To do this, INC AX ; multiply the number of entrys MOV LOOKUP_SIZE,AX ; in the lookup table by the MOV CL,PAGE_SIZE ; page size and the sector size. XOR CH,CH MUL CX MOV CX,256 ;Correct for computing twice the MUL CX ; number of lookup table entrys MOV CX,4 ; by halving the sector size. MEM_LOOP1: ;Convert requested memory into SHR DX,1 ; paragraphs. RCR AX,1 LOOP MEM_LOOP1 ;----------------------------------------------------------------------------- ;Check which memory to use. ;----------------------------------------------------------------------------- CMP EMS_FLAG,1 JNE GET_DOS_MEM ;----------------------------------------------------------------------------- ;Request memory from EMS driver. ;----------------------------------------------------------------------------- MOV CX,10 EMS_REQ_LOOP1: SHR DX,1 ;Convert paragraphs to EMS pages. RCR AX,1 ; Each page is 16K big. LOOP EMS_REQ_LOOP1 ;----------------------------------------------------------------------------- ;Check to see if there is enough EMS memory to hold the cache. ;----------------------------------------------------------------------------- MOV CX,AX ;save number of ems pages needed MOV AH,42H INT 67H OR AH,AH ;check for error JNE EMS_ERROR CMP BX,CX ;compare available pages with need JAE GET_EMS_SEG JMP MEMORY_ERROR ;----------------------------------------------------------------------------- ;Find out the segment of the EMS page frame. ;----------------------------------------------------------------------------- GET_EMS_SEG: MOV AH,41H ;get page frame address command INT 67H ;call EMS driver OR AH,AH ;check for error JNE EMS_ERROR MOV CACHE_SEGMENT,BX ;save page frame segment address MOV MAX_SEGMENT,BX MOV SIZE_MASK,0 ;Request the memory from EMS driver. MOV AH,43H ;EMS request memory function MOV BX,CX ;put number of EMS pages in bx INT 67H ;call EMS driver OR AH,AH ;check for error JNE EMS_ERROR MOV EMS_HANDLE,DX ;save EMS handle. MOV AX,ADDR_MASK ;Create the EMS mask from the MOV CL,3 ; addr mask SHR AX,CL MOV EMS_MASK,AX ;Compute the amount of resident memory needed. MOV DX,LOOKUP_SIZE ;Get back size of lookup table ADD DX,OFFSET DATA_START+15 MOV CL,4 SHR DX,CL ;convert memory into paragraphs MOV TERM_MEM,DX JMP SHORT PRINT_INSTALL_MSG ;----------------------------------------------------------------------------- ;Error routines for memory requests. ;----------------------------------------------------------------------------- EMS_ERROR: MOV DX,OFFSET HELP8 ;EMS error JMP HELP_ROUTINE ;----------------------------------------------------------------------------- ;Get memory from DOS. Try to reduce memory for program to see if there is ; enough memory for the cache. ;----------------------------------------------------------------------------- GET_DOS_MEM: ;----------------------------------------------------------------------------- ;Move the stack to a safe place inside the cache. ;----------------------------------------------------------------------------- CLI ;Inhibit interrupts during this MOV BX,SP ; time. MOV SP,4000H ;Move the stack pointer down ; closer to the code, and well STI ; with in the cache memory. ;----------------------------------------------------------------------------- ;Check size of cache memory, then reduce current allocation to minimum. ;----------------------------------------------------------------------------- OR DX,DX ;allow cache size <= 512K JNE MEMORY_ERROR ; for DOS memory. MOV BX,OFFSET DATA_START+15 ;compute start of cache ADD BX,LOOKUP_SIZE MOV CL,4 ;convert to segment. SAR BX,CL MOV DX,CS ;Get the current code segment ADD DX,BX ;Add the converted offset MOV CACHE_SEGMENT,DX ;save the cache segment ;----------------------------------------------------------------------------- ;Continue on with allocating the proper amount of DOS memory. ;----------------------------------------------------------------------------- ADD BX,AX ;Add size of cache. MOV TERM_MEM,BX ;reduce to amount of memory needed MOV AH,4AH ; at termination of the program. INT 21H ;DOS reallocate memory function JC MEMORY_ERROR ;es already points to code seg. ;----------------------------------------------------------------------------- ;Create size mask from address mask ;----------------------------------------------------------------------------- MOV CX,ADDR_MASK ;The last part of the DOS memory XCHG CH,CL ; installation is to create the SHR CX,1 ; size mask needed. AND CX,0FC00H ;Create size mask from addr mask MOV SIZE_MASK,CX MOV AX,CACHE_SEGMENT ADD AX,CX ;Add size mask to cache_segment MOV MAX_SEGMENT,AX ; register to generate max segment ;----------------------------------------------------------------------------- ;Tell user that cache is installed. ;----------------------------------------------------------------------------- PRINT_INSTALL_MSG: MOV DX,OFFSET MSG1 MOV AH,9 INT 21H ;----------------------------------------------------------------------------- ;Redirect interrupt vector 13. ;----------------------------------------------------------------------------- MOV AL,ENABLED ;save the state of the enable flag PUSH AX MOV ENABLED,0 ;disable cache until ready to exit MOV AX,3513H ;Get the old int 13h vector INT 21H MOV OLD_INT13H,BX ;Save the old vector MOV OLD_INT13H[2],ES MOV DX,OFFSET DISK_INT ;Point int 13h to cache routine. MOV AX,2513H INT 21H ;----------------------------------------------------------------------------- ;Terminate but remain resident. ;----------------------------------------------------------------------------- MOV DX,TERM_MEM ;get amount of memory needed. MOV AX,3100H ;Terminate but stay resident JMP INSTALL1 ;jump to location above the ; lookup table so it can be ; cleared. ;----------------------------------------------------------------------------- ;Routine to print installaion error messages. ;----------------------------------------------------------------------------- MEMORY_ERROR: MOV DX,OFFSET MSG2 ;Print DOS memory error MOV AH,9 INT 21H MOV AX,4C02H ;terminate with rc = 2. INT 21H ;----------------------------------------------------------------------------- ;Select disk drive to cache ;----------------------------------------------------------------------------- DISK_SELECT PROC NEAR MOV DL,2[DI] ;read number after /h SUB DL,30h ;convert ascii nubmer to binary JL DISK_SEL_ERR1 ;allow only the numbers 0-9. CMP DL,9 JA DISK_SEL_ERR1 OR DL,80H ;consider only fixed disks MOV DISK_NUM,DL ;Store drive number CLC RET DISK_SEL_ERR1: MOV DX,OFFSET HELP9 ;illegal disk has been selected. STC RET DISK_SELECT ENDP ;----------------------------------------------------------------------------- ;Expanded memory select ;----------------------------------------------------------------------------- EXPANDED_MEM PROC NEAR ;Test for the EMS driver. PUSH ES PUSH DI MOV AX,3567H ;Get EMS vector INT 21H MOV DI,0AH ;Using the segment from the 67h MOV SI,OFFSET EMS_HEADER ; vector, look at offset 0ah. MOV CX,8 ; Compare the next 8 bytes with CLD ; the expected ems header. If REPE CMPSB ; they are the same, allow ems POP DI ; option, else, print error msg. POP ES ;Remember, poping registers does JNE EMS_NOT_THERE ; not change the flags ;Set ems indicator. INC EMS_FLAG ;indicate EMS option CLC RET ;check for more commands EMS_NOT_THERE: MOV DX,OFFSET HELP7 ;display error message and exit STC RET EXPANDED_MEM ENDP ;----------------------------------------------------------------------------- ;Determine the size of the cache. ;----------------------------------------------------------------------------- CACHE_SIZE PROC NEAR MOV AX,2[DI] ;get the number after the /m MOV SI,OFFSET MEM_SIZE_TBL MOV CX,2 CACHE_SIZE_LOOP1: CMP AX,[SI] ;Search the size table to find a JE SIZE_FOUND ; match for the size on the INC CX ; command line. ADD SI,2 CMP SI,OFFSET MEM_SIZE_TBL_END JBE CACHE_SIZE_LOOP1 MOV DX,OFFSET HELP1 ;if size unrecognised, display err STC RET SIZE_FOUND: XOR BX,BX ;clear register for mask gen. CACHE_SIZE_LOOP2: STC ;shift 1's into the low bit of bx RCL BX,1 ;continue to shift 1's until the LOOP CACHE_SIZE_LOOP2 ; count id exausted. SAL BX,1 MOV ADDR_MASK,BX CLC RET CACHE_SIZE ENDP ;----------------------------------------------------------------------------- ;Enable or disable the cache ;----------------------------------------------------------------------------- CACHE_ON_OFF PROC NEAR MOV AL,2[DI] ;Get next letter in command line CMP AL,5AH ;Convert uppercase to lower JA ON_OFF_SKIP ; case if needed. ADD AL,20H ON_OFF_SKIP: XOR CX,CX PUSH ES MOV ES,OTHER_SEG ;Get segment of copy (if any) ASSUME ES:NOTHING CMP AL,'f' ;check second letter for on or off JE CACHE_OFF1 INC CX CMP AL,'n' JNE CACHE_ON_OFF_ERR CACHE_ON1: CMP ALRDY_IN_MEM,CH ;If initial instalation, don't JE CACHE_OFF1 ; clear the lookup table here. CALL RESET_CACHE CACHE_OFF1: MOV ES:ENABLED,CL ;Set flag to enable cache POP ES CLC RET CACHE_ON_OFF_ERR: POP ES MOV DX,OFFSET HELP3 ;indicate an illegal command STC RET CACHE_ON_OFF ENDP ;----------------------------------------------------------------------------- ; UNINSTALL deallocates the memory block addressed by ES and restores the ; interrupt 13 vector displaced on installation. ; Exit: CF clear - program uninstalled ; CF set - can't uninstall ;----------------------------------------------------------------------------- UNINSTALL PROC NEAR ASSUME DS:CODE PUSH ES MOV AX,3513H ;Get int 13 vector INT 21H MOV AX,ES ;Compare vector segment with CMP AX,OTHER_SEG ; segment of installed code. JNE REMOVE_ERR ;If not the same, can't remove. ;----------------------------------------------------------------------------- ;Release the memory occupied by the program. ES already has proper segment. ;----------------------------------------------------------------------------- CMP ES:EMS_FLAG,0 ;See if EMS memory or conventional JE REMOVE_SKIP1 MOV DX,ES:EMS_HANDLE ;If EMS memory, deallocate using MOV AH,45H ; function 6. INT 67H OR AH,AH JNE REMOVE_ERR REMOVE_SKIP1: MOV AH,49H ;DOS free memory function INT 21H JC REMOVE_ERR ;If carry, error on removal ;----------------------------------------------------------------------------- ;Restore interrupt 13h vector. ;----------------------------------------------------------------------------- PUSH DS LDS DX,ES:[OLD_DISK_INT] ;Get old vector from installed MOV AX,2513H ; code. INT 21H ;Set int 13 to old vector. POP DS JC REMOVE_ERR ;If error, report and exit. ;----------------------------------------------------------------------------- ;Destroy the ASCII fingerprint that identifies the code and exit. ;----------------------------------------------------------------------------- NOT WORD PTR ES:[ENTRY] CLC ;Clear error flag REMOVE_EXIT: POP ES RET ;----------------------------------------------------------------------------- ;The program can't be uninstalled. Set CF and exit. ;----------------------------------------------------------------------------- REMOVE_ERR: MOV DX,OFFSET HELP10 ;Point to error message. STC ;Set error flag JMP SHORT REMOVE_EXIT UNINSTALL ENDP MAIN ENDP END_OF_PROG = $ CODE ENDS END ENTRY