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Assembly Source File | 1994-03-21 | 18.1 KB | 539 lines

page 55,132 title "PERUSEE = EMS interface for PERUSE" ; --------------------------------------------------------------------- ; ; PERUSEE - EMS interface for PERUSE ; First Published in PC Magazine April 12, 1994 ; ; --------------------------------------------------------------------- ; --------------------------------------------------------------------- ; $lgb$ ; 1.0 02/09/94 RVF Final beta complete. Can release if ; + no other errors found. ; 1.1 03/21/94 RVF Added proper mask when allocating ; + memory ; $lge$ ; --------------------------------------------------------------------- ; $nokeywords$ ; ----------------------------------------------------------------------- ; ; Buffer Memory Interface Routines ; ; ----------------------------------------------------------------------- ; The folowing routines serve as the interface to the buffer memory. ; ; All (or in this case, both) modules have the same inteface that ; allows use of the buffer storage without the utilitie's specific ; knowledge of what memory is in use. ; ; Each module has a standard header that consists of the following: ; ; 2 byte length of module ; 1 byte module identifier (E = EMX, X = XMS) ; Note: Must be upper case ; JMP instrution to main entry point ; ; Nothing is guaranteed beyond the header. ; ; The module must be completely self contained, lying completely within ; it's own segment. Any references within the segment must be relative ; to that segment since PERUSE moves the module, in its entirety, to ; another segment aligned address where it is actually executed. ; ; ----------------------------------------------------------------------- ; ; Here are the specific calling sequences: ; ; ----------------------------------------------------------------------- ; General Return ; -------------- ; If any error occurs, the function sets the carry flag. ; ; carry flag = error ; Initialize Scroll Memory ; ------------------------ ; This call checks that the requested type of memory exists in ; sufficient quantity to complete the call. If so, it allocates the ; the memory and stores any information needed to access the memory. ; ; ax = 00h ; cx = number of 1k records needed ; Read scroll record ; ------------------ ; This function reads a record from the scroll buffer. If there are ; n used records in the scroll buffer, the application may request ; record numbers 0 to n-1. The contents of the record are placed in ; the buffer located at es:dx. ; ; The most recent record is considered record 0 and the oldest is n-1. ; ; ax = 01h ; bx = record number; where: 0=oldest record, n-1=most recent ; es:di -> buffer ; Write scroll record ; ------------------- ; This function writes a new record to the scroll buffer. If the ; scroll buffer has already filled, the oldest record is overwritten. ; ; ax = 02h ; ds:bx -> buffer to write ; Get number of used records ; -------------------------- ; This function returns the number of records used in the scroll buffer. ; ; ax = 03h ; ; returns: ; ax = number of records used ; Release scroll buffer ; --------------------- ; This function is called to release the scroll buffer before removing ; the TSR from memory. If this function is not called, the scroll ; buffer will not be released until the system is rebooted. ; ; ax = 04h ; Save record pointer ; ------------------- ; This function saves the current record information maintained by the ; interface routine. Any future records written to the buffer can then ; be "unsaved" by calling function 6. ; ; ah = 05h ; Restore pointers ; ---------------- ; This function restores the record pointers saved with function 5. ; Furthermore, it clears any records written after the save. ; ; ax = 06h ; ---------------------------------------------------------------------- MaxFunction = 6 ; Maximum function number RecSize = 1024 ; record size ; ---------------------------------------------------------------------- ; ; EMS Interface Routine ; ; ---------------------------------------------------------------------- EmsInt segment para public 'code' ; EMS interface assume cs:EmsInt ; called via far call EmsStart: EmsLen dw EmsEnd ; length of module db 'E' ; module identifier jmp short Ems ; jump to dispatcher Ems67v equ word ptr ds:[67h * 4] ; offset for int 67h (EMS) EmsSig db 'EMMXXXX0' ; EMS driver signature EmsRecs dw 0 ; records allocated EmsUsed dw 0 ; records used EmsOld dw 0 ; oldest record EmsSUsed dw 0 ; saved records used EmsSOld dw 0 ; saved oldest record EmsWrites dw 0 ; writes since save EmsHndl dw 0 ; EMS handle EmsFrame dw 0 ; segment of page frame EmsTbl label byte ; function dispatch table dw Ems0 ; Initialize dw Ems1 ; Read Record dw Ems2 ; Write Record dw Ems3 ; Get number of records dw Ems4 ; Free EMS memory dw Ems5 ; Save 4k dw Ems6 ; Restore 4k ; --------------------- ; Interface Entry Point ; --------------------- Ems proc Far ; dispatch the call push si ; save registers push ds push es cmp ax, MaxFunction ; q. out of range? ja EmsRtnErr ; a. yes .. error shl ax, 1 ; ax = ax * 2 (table index) mov si, ax ; si = table index jmp word ptr cs:EmsTbl[si] ; go to the routine ; -------------- ; Error return.. ; -------------- EmsRtnErr: stc ; set the carry bit pop es ; restore pop ds ; ..saved pop si ; .. ..registers ret ; return with error ; ----------- ; Return OK.. ; ----------- EmsRtnOk: clc ; reset carry bit pop es ; restore pop ds ; ..saved pop si ; .. ..registers ret ; return OK ; -------------------------------------------------- ; Initialization; cx = number of records to allocate ; -------------------------------------------------- Ems0 label byte push bx ; save registers push dx push di push si mov cs:EmsRecs, cx ; save records requested xor ax, ax ; clear ax mov ds, ax ; ds -> low memory mov ax, Ems67v+2 ; ax = int 67's segment mov ds, ax ; ds -> int 67's segment mov si, 0ah ; ds:si -> signature, if any push cs ; save our segment pop es ; es -> our segment lea di, cs:EmsSig ; si -> signature expected cld ; ensure incremental compare mov cx, 8 ; bytes to test repe cmpsb ; q. EMS found? jne Ems0Err ; a. no .. error ; ; Get the page frame segment ; mov ah, 41h ; ah = get page frame address int 67h ; get the page frame or ah, ah ; q. any problem? jne Ems0Err ; a. yes .. error mov cs:EmsFrame, bx ; save the segment ; ; EMS found .. Allocate the buffer (if possible) ; mov bx, cs:EmsRecs ; bx = number of records req'd add bx, 15 ; Round up .. and bx, 0fff0h ; ..to next 16 mov cs:EmsRecs, bx ; save in records available mov cl, 4 ; cl = shift counter shr bx, cl ; bx = bx / 16 mov ah, 43h ; ah = allocate memory int 67h ; ..ask EMS for the memory or ah, ah ; q. memory found? jne Ems0Err ; a. no .. error mov cs:EmsHndl, dx ; save the handle ; ; Return with no error .. ; pop si ; restore registers pop di pop dx pop bx jmp EmsRtnOk ; ..return no error ; ; Return with an error .. ; Ems0Err: pop si ; restore registers pop di pop dx pop bx jmp EmsRtnErr ; ..return w/error ; ------------------------------------------------ ; Read record; bx = record number; es:di -> buffer ; ------------------------------------------------ Ems1 label byte cmp bx, cs:EmsUsed ; q. valid record number? jae EmsRtnErr ; a. no .. exit now push cx ; save registers push dx push di mov ah, 47h ; ah = save page map mov dx, cs:EmsHndl ; dx = our handle int 67h ; save current map add bx, cs:EmsOld ; add in oldest record number cmp bx, cs:EmsUsed ; q. beyond end of buffer? jb Ems1$10 ; a. no .. use this number sub bx, cs:EmsUsed ; bx = record number Ems1$10: mov si, bx ; si = real record number mov cl, 4 ; cl = shift counter shr bx, cl ; bx = bx / 16 (EMS page number) and si, 0fh ; si = record in page mov cl, 10 ; cl = shift counter shl si, cl ; si = si * 1024 (offset in page) mov ax, 4400h ; ax = map into frame page 0 int 67h ; ..get the page from EMS push ax ; save return code mov ds, cs:EmsFrame ; ds:si-> record in EMS cld ; assure incremental move mov cx, RecSize/2 ; ..512 words (or 1024 bytes) rep movsw ; ..move the record mov ah, 48h ; ah = restore page map int 67h ; ..ask EMS to do it pop ax ; restore return code or ah, ah ; q. any error in map page? jnz Ems1Err ; a. yes .. return with error ; ; Return with no error .. ; pop di ; restore registers pop dx pop cx jmp EmsRtnOk ; return without error ; ; Return with an error .. ; Ems1Err: pop di ; restore registers pop dx pop cx jmp EmsRtnErr ; return with error ; ------------------------------------ ; Write record; ds:bx -> record buffer ; ------------------------------------ Ems2 label byte push bx ; save registers push cx push dx push di mov si, bx ; ds:si -> record mov bx, cs:EmsUsed ; bx = records used cmp bx, cs:EmsRecs ; q. all records used? jnb Ems2$10 ; a. yes .. use old to calc inc cs:EmsUsed ; Add to used records jmp short Ems2$20 ; ..continue Ems2$10: mov bx, cs:EmsOld ; bx = next record to write lea ax, 1[bx] ; ax = bx + 1 (next old record) cmp ax, cs:EmsRecs ; q. hit the top of buffer? jb Ems2$15 ; a. no .. continue xor ax, ax ; else .. ax = first rec in EMS Ems2$15: mov cs:EmsOld, ax ; EmsOld = oldest record number ; ; When we get here, bx contains the record number ; Ems2$20: mov di, bx ; di = record number mov cl, 4 ; cl = shift counter shr bx, cl ; bx = bx / 16 (EMS page number) and di, 0fh ; di = record in page mov cl, 10 ; cl = shift counter shl di, cl ; di = di * 1024 (offset in page) mov ah, 47h ; ah = save page map mov dx, cs:EmsHndl ; dx = our handle int 67h ; save current map mov ax, 4400h ; ax = map into frame page 0 int 67h ; ..get the page from EMS or ah, ah ; q. any error in map page? jnz Ems2Err ; a. yes .. return with error mov es, cs:EmsFrame ; es:di -> record in EMS cld ; assure incremental move mov cx, RecSize/2 ; ..512 words (or 1024 bytes) rep movsw ; ..move the record ; ; Return with no error .. ; mov ah, 48h ; ah = restore page map mov dx, cs:EmsHndl ; dx = our handle int 67h ; ..ask EMS to do it inc cs:EmsWrites ; ..increment write counter pop di ; restore registers pop dx pop cx pop bx jmp EmsRtnOk ; return without error ; ; Return with an error .. ; Ems2Err: mov ah, 48h ; ah = restore page map mov dx, cs:EmsHndl ; dx = our handle int 67h ; ..ask EMS to do it pop di ; restore registers pop dx pop cx pop bx jmp EmsRtnErr ; return with error ; -------------------------- ; Get number of used records ; -------------------------- Ems3 label byte mov ax, cs:EmsUsed ; ax = records used jmp EmsRtnOk ; ..return ok ; --------------------- ; Release scroll buffer ; --------------------- Ems4 label byte push dx ; save registers mov ah, 45h ; ah = deallocate EMS pages mov dx, cs:EmsHndl ; dx = our EMS handle int 67h ; ..Hey, EMS, deallocate it! pop dx jmp EmsRtnOk ; return no error Ems endp ; -------------------- ; Save record pointers ; -------------------- Ems5 label byte push cs:EmsUsed ; save records used pop cs:EmsSUsed ; ..in save field push cs:EmsOld ; save oldest record pop cs:EmsSOld ; ..in save field mov cs:EmsWrites, 0 ; zero write counter jmp EmsRtnOk ; ..return without error ; ----------------------- ; Restore record pointers ; ----------------------- Ems6 label byte push cs:EmsSUsed ; reload used field pop cs:EmsUsed ; ..from save field push cs:EmsSOld ; reload oldest record pop cs:EmsOld ; ..from save field mov ax, cs:EmsWrites ; return number of writes jmp EmsRtnOk ; ..return without error align 16 ; boundary for next driver EmsEnd label byte EmsInt ends IFNDEF Borland ; Assemble in MASM only ENDSTMT macro ; macro only needed with MASM end EmsStart ; end the assembly endm ENDIF ENDSTMT ; varies with Tasm and Asm