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Assembly Source File | 1984-05-03 | 62KB | 1,136 lines

PAGE 60,132 ;*************************************************************************** ; General comments ;*************************************************************************** ; The following comprises the disassembled and documented version of DOS-ED ; as it exists on Compuserve's XA6 data base. If one reassembles this ; program one will obtain the exact version of DOS-ED.COM that exists on ; that database. No attempt has been made to make improvements to this code ; other than to indicate in the margin were some could (and probably should) ; be made. If you notice that the program sizes are different between this ; reassembled and relinked version and the version that has been generated ; from the HEX file on CIS, that is because there is some trailing garbage ; on the CIS file. You can strip it off in the debugger and the files will ; compare exactly. ; ; Even after disassembling and documenting this code I have a few questions ; about what was being done in places. If my comments seem spurious at ; times, then just take them with a grain of salt. They should help you ; understand this code for the most part. ; ; When linking this program you should expect to receive a No Stack warning ; message along with an Unsatisfied external error on DOS_RETURN. These ; are normal and should be ignored. ; ; DOS-ED is a fine piece of programming performed by Jack Gersbach. ; This disassembly and documentation was done by myself. ; - Scott W. Killen ; ;*************************************************************************** ; Definitions and commentary on conventions in coding ;*************************************************************************** ; Register usage: (Most common (but not exclusive) uses are listed) ; AX, DX, CX - Used for many reasons ; DH - Usually current row on crt ; DL - Usually current col on crt ; SI - Usually points to offset of current character in input buffer (first character is offset 0) ; DI - Usually has the value of one of the following: ; * The number of characters currently in the input buffer *or* ; * Points to a destination in the text holding buffer ; BX - Usually contains the address at which the first character in the input buffer is located. ; (The two characters before this are the max buffer size and length of string ; characters.) ; BP - Usually a register of flags organized as bits |01234567| where: ; Bits 0-3 have no function ; Bit 4 - Off means the input buffer has been altered since interrupt processing began. ; On means *only* lateral cursor positioning commands have been issued since interrupt ; processing began. ; Bit 5 - Off means previous line from holding buffer, On means original line ; Bit 6 - Off means no changes to current line in input buffer, On means changes have been made ; Bit 7 - Applies to the redisplay of lines on the screen after an intra-line edit operation ; Off means line wasn't shortened therefore no trailing blanks needed ; On means line is now shorter and blanks are needed over trailing characters ; ; Memory Usage: ; ES:[0450H] - Contains current cursor position in Bios data area ; ES:[044AH] - Contains # of columns of current crt screen in Bios data area ; ES:[0417H] - Keyboard flag, containing insert, shift, num lock, scroll lock etc in Bios data area ; insert flag bit is 80h ; ; CS:[inline_mod1+1] - Jump return address to normal DOS funcion processing ; CS:[inline_mod2+1] - Current cursor definition (start/stop lines) ; CS:[inline_mod3+1] - Screen location of end of line (row/col) ; CS:[inline_mod4+2] - Higher of DS or CS on entry into interrupt. ; CS:[inline_mod5+2] - Maximum size of input buffer ; ; start_off - Offset of start of input buffer on screen (example if prompt is A> then screen column position ; of input buffer start would be 2 ; current_col - Current column position on screen (1st column is 0) ; last_entry - Address (offset) of last string accessed in text buffer ; next_entry - Address (offset) of next available block in text buffer ; buffer_bot - Base address of text buffer ; buffer_top - Top address of text buffer ; aux_last \ ; aux_next \ Same as previous four except for auxiliary buffer ; aux_bot / ; aux_top / ; ; Character equates ACK equ 06h ; Acknowledge character (Cntrl F) BELL equ 07h ; Bell character (Cntrl G) BACKSPACE equ 08h ; Backspace character TAB equ 09h ; Tab character ESC equ 1Bh ; Escape character BLANK equ 20h ; Space character CR equ 0dh ; carriage return LF equ 0ah ; Line feed HAT equ 5eh ; "^" character SMALLA equ 61h ; "a" character LEFT_CURLY_BRACE equ 7Bh ; "{" character CNTL_BACKSPACE equ 7fh ; Control and backspace pressed simultaneously ; Masks INSERT_ON_MASK equ 80h ; Insert key bit on, corresponding to keyboard status word INSERT_OFF_MASK equ 7fh ; Insert key bit off, corresponding to keyboard status word LENGTH_BYTE_MASK equ 80h ; Mask to identify the text string length bit in text buffer LENGTH_OFF_MASK equ 7fh ; Mask to turn of the length byte identifier UPPER_CASE_MASK equ 40h ; Convert control character to upper case character LOWER_CASE_MASK equ 20h ; Convert upper case character to lower case character ; Physical characteristics ROWS_ON_CRT equ 19h ; Ordinal number of lines on crt LAST_ROW_ON_CRT equ ROWS_ON_CRT - 1 ; Offset of last line on crt (top line is line 0) MONO_CUR_DEF equ 0B0Ch ; Start, stop lines of cursor MONO_CUR_STOP equ 0Ch ; Stop line for standard cursor GRAPHICS_CUR_DEF equ 0607h ; Start, stop lines of cursor for graphics device GRAPHICS_CUR_STOP equ 07h ; Stop line for standard cursor for graphics device TEXT_BUFFER_START equ 60h ; Start address for text holding buffer TEXT_BUFFER_END equ 160h ; End address for text holding buffer TEXT_BUFFER_SIZE equ TEXT_BUFFER_END - TEXT_BUFFER_START ; Extent of text buffer BOTH_BUFFS_SIZE equ TEXT_BUFFER_SIZE + TEXT_BUFFER_SIZE ; Combined buffer size AUX_BUFFER_START equ 160h ; Auxiliary holding buffer start address AUX_BUFFER_END equ 260h ; Auxilliary holding buffer end address ; *NOTE* TEXT_BUFFER_END - TEXT_BUFFER_START = ; AUX_BUFFER_END - AUX_BUFFER_START ; Bios interrupt 10 functions SET_CURSOR_TYPE equ 01h SET_CURSOR_POSN equ 02h READ_CURSOR_POSN equ 03h READ_VIDEO_STATE equ 0fh ; Dos interrupt 21 functions INPUT_CHR_NOECHO equ 08h OUTPUT_CHR equ 02h ;*************************************************************************** ; BIOS data segment definition ;*************************************************************************** BIOSEG SEGMENT at 0h org 417h kbd_flag db ? org 44ah crt_cols dw ? org 450h cursor_posn dw ? BIOSEG ends ;*************************************************************************** ; DOS-ED code segment begins ;*************************************************************************** CSEG SEGMENT ASSUME CS:CSEG ORG 100H DOSED PROC NEAR MOV SI,offset loadlabel ; Source of code to move is at loadlable MOV DI,offset initialize ; Destination is at end of file at initialize MOV CX,offset line_table ; Above the code to be moved is linetable SUB CX,SI ; The difference is the amount of code to be moved repz MOVSB ; Move it!! JMP initialize ; Now go do it. loadlabel: XOR AX,AX ; Clear AX MOV DS,AX ; Prepare to save original interrupt MOV SI,0084H ; Source for INT 21h as provided for in the interrupt table MOV DI, offset [inline_mod1+1] ; Destination in the code segment for moving this pointer MOVSW ; Move the two word address MOVSW MOV AX, offset entry_point ; Move this programs starting address into the dos interrupt slot MOV [SI-04H],AX ; Move offset in line MOV [SI-02H],CS ; Move segment value in line MOV DI, TEXT_BUFFER_START ; Working buffer begins at offset 60h which is Formatted parameter MOV CX, BOTH_BUFFS_SIZE ; area 1 in the Program Segment Prefix. MOV AL, CR ; Fill 512 bytes with CR characters. Note that this technique uses repz STOSB ; 161 bytes of PSP for storage! Very Clever! MOV DX, offset initialize ; Dos may load above this address INT 27H ; Terminate but stay resident line_table db 300 dup (?) entry_point: CMP AH,0AH ; Is this function 10? JE wrapper ; Nope, continue with normal Dos 21 interrupt EXTRN DOS_RETURN:FAR inline_mod1: JMP DOS_RETURN ; This code is modified in line! ; Go to normal Dos function handling. wrapper: PUSH AX PUSH BX PUSH CX PUSH DX PUSH SI PUSH DI PUSH BP PUSH DS PUSH ES STI CALL begin_dosed POP ES POP DS POP BP POP DI POP SI POP DX POP CX POP BX POP AX MOV AL,00H IRET ;*************************************************************************** ; Extended keystroke recognition and branching tables ;*************************************************************************** ; Table 1 of extended keyboard function codes table1: t1_1 db 0fh ; Back Tab t1_2 db 47h ; Home key t1_3 db 48h ; Up arrow t1_4 db 4bh ; Left arrow t1_5 db 4dh ; Right arrow t1_6 db 4fh ; End key t1_7 db 50h ; Down Arrow t1_8 db 53h ; Del key t1_9 db 73h ; Cntrl Left Arrow t1_a db 74h ; Cntrl Right Arrow t1_b db 75h ; Cntrl End t1_c db 77h ; Cntrl Home t1_d db 76h ; Cntrl PgDn t1_e db 84h ; Cntrl PgUp t1_f db 00h ; ? ; Table 2 indexes correspond to table 1 indexes ; and points to code address where the function is handled. table2: t2_f dw offset error_return ; 0ah, 05h ; ? t2_e dw offset cntrl_page_up ; 74h, 07h ; Cntrl PgUp t2_d dw offset cntrl_page_down ; 0a9h, 06h ; Cntrl PgDn t2_c dw offset cntrl_home ; 0bh, 05h ; Cntrl Home t2_b dw offset cntrl_end ; 27h, 05h ; Cntrl End t2_a dw offset cntrl_right_arrow ; 41h, 05h ; Cntrl Right Arrow t2_9 dw offset cntrl_left_arrow ; 83h, 05h ; Cntrl Left Arrow t2_8 dw offset del_key ; 0edh, 05h ; Del key t2_7 dw offset down_arrow ; 44h, 06h ; Down Arrow t2_6 dw offset end_key ; 0e4h, 04h ; End key t2_5 dw offset right_arrow ; 67h, 05h ; Right arrow t2_4 dw offset left_arrow ; 99h, 05h ; Left arrow t2_3 dw offset up_arrow ; 43h, 06h ; Up arrow t2_2 dw offset home_key ; 0e1h, 05h ; Home t2_1 dw offset backtab ; 8dh, 05h ; Backtab ;*************************************************************************** ; Display and output services ;*************************************************************************** screen_and_display: ; Screen out control characters of form ^x CMP AL, BLANK ; Compare AL to blank character JNB display_one_char ; If we have a printable character go to display routine CMP AL, TAB ; Is this a forward tab? JE display_one_char ; If so, go display. PUSH AX ; No, this is a "normal" control character MOV AL,HAT ; Place a "^" character in AL CALL display_one_char ; Print the "^" out. POP AX ; Now convert the Control character to its OR AL, UPPER_CASE_MASK ; upper case equivalent and print it. Result is "^E" ; construct for representing control characters. display_one_char: CMP AL, BLANK ; Does AL contain a blank character JB display_cntrl_chr ; Jump if we have a control character ready_display: CMP AL, CNTL_BACKSPACE ; Don't increment column counter if this JE output_to_display ; is a control Backspace character INC BYTE PTR CS:[current_col] ; Increment column position because we received ; something printable output_to_display: PUSH DX ; Save the DX register and set up the XCHG AX,DX ; AH register for a DOS function 2 (Display MOV AH, OUTPUT_CHR ; output) call. INT 21H XCHG AX,DX ; Restore the AX register POP DX ; and restore the DX register RET display_cntrl_chr: ; Process a control character for output CMP AL, CR ; Is this a carriage return character? JE cr_out ; If so go take care of it CMP AL, BACKSPACE ; Is this a backspace? JE bs_out ; If so we need to take care of it CMP AL, TAB ; Maybe its a tab character JNE relay_to_output ; Continue if its not a tab MOV AL,BYTE PTR CS:[current_col] ; Set AL to current column on screen OR AL,0F8H ; Get the number of spaces to the next NEG AL ; 8 byte boundary PUSH CX ; Save the CX register MOV CL,AL ; Place the count of blanks to be output in CL mov ch, 00h ; Zero out high byte JCXZ skip_tabbing ; Dont do anything if count is zero tab_loop: MOV AL, BLANK ; Ok, now print out all necessary CALL display_one_char ; blanks to reach an 8 character LOOP tab_loop ; boundary. skip_tabbing: POP CX ; Restore the CX register. RET cr_out: MOV CS:BYTE PTR [current_col],00H ; Reset current column pointer to zero relay_to_output: JMP SHORT output_to_display bs_out: DEC BYTE PTR CS:[current_col] ; Decrement the current column pointer PUSH AX ; Save the character in register AX PUSH DX ; Save the DX register MOV DX,ES:[0050H] ; Get the Cursor position from Bios data area MOV AH,ES:[004AH] ; Get the # of CRT cols on screen from Bios data area OR DL,DL ; Are we at column zero? JNE bs_end ; If not forget the rest. OR DH,DH ; Are off the screen at the top? JNE set_cur_loc ; If not then dont reset rows MOV DH, ROWS_ON_CRT ; (Re)set row value to 25 set_cur_loc: DEC DH ; Decrement the row count MOV DL,AH ; Move in # of columns. (0, 0) is home. PUSH BX ; Save BX MOV BH,00H ; Prepare for BIOS interrupt 10 funtion 2 MOV AH, SET_CURSOR_POSN ; call (Set cursor position) INT 10H ; Do it. POP BX ; Restore BX bs_end: POP DX ; Restore DX register POP AX ; and the AX register JMP SHORT relay_to_output ; and now we are done. decrement_col_row: ; Wrap back if line spans two screen lines OR DL,DL ; Are we at column zero JNE dcr_end ; If so then dont worry about row update DEC DH ; Yep, decrement the row pointer MOV DL,BYTE PTR ES:[crt_cols] ; Get the # of CRT cols per screen from Bios data area dcr_end: DEC DL ; Decrement the column pointer RET display_blank: MOV AL, BLANK display_and_test: ; Display and test for updated cursor location PUSH CX ; Save CX register MOV CX,ES:[cursor_posn] ; Load CX with cursor position from Bios CALL screen_and_display ; Send the character in AL to output display CMP CH, LAST_ROW_ON_CRT ; Are we on the last row? JNE dat_end ; If not then no further tests are needed CMP CL,BYTE PTR ES:[cursor_posn] ; Are we now on a new column? (alternative question ; is: have we scrolled?) JBE dat_end ; If current location > cl then yes we have scrolled ; up a line and need to decrement the line pointer DEC DH ; Decrement the line pointer dat_end: POP CX ; Restore CX RET ;*************************************************************************** set_cursor: PUSH BX PUSH CX PUSH DX PUSH BP ; Save registers PUSH SI PUSH DI inline_mod2: MOV CX, MONO_CUR_DEF ; Assume Standard char def ; (Note that this word is modified ; in line if it is later determined ; that a graphics board is in use) TEST BYTE PTR ES:[kbd_flag], INSERT_ON_MASK ; Is insert on? JE after_box ; If not then branch MOV CH,CL ; Yep, turn the cursor into SHR CH,1 ; a half sized box after_box: MOV AH, SET_CURSOR_TYPE ; Set up and call Bios for INT 10H ; support. POP DI POP SI POP BP ; Restore Registers POP DX POP CX POP BX MOV AX,WORD PTR ES:[cursor_posn] ; Load AX with current cursor position inline_mod3: CMP AX,0888H ; Compare current cursor position to end of line position JB sc_ret ; If less than then dont update end of line position MOV CS:WORD PTR [inline_mod3+1],AX ; Modify end of line address with value of current cursor position sc_ret: RET credit db 'DOS EDITOR BY J. Gersbach',CR,LF,00 begin_dosed: ; Save registers PUSH BX PUSH CX PUSH DX MOV BH,00H ; Set up to read current cursor position MOV AH, READ_CURSOR_POSN ; Cursor position returned as DH, DL is row, col INT 10H ; Read the current cursor position into DH, DL MOV CS:[start_off],DL ; Move current column into storage MOV CS:[current_col],DL ; Move current column into storage CMP CL, MONO_CUR_STOP ; Check: Is current end line for cursor = 12 JB bd2 ; Branch if less than 12 MOV AH, READ_VIDEO_STATE ; Set up to return current video state INT 10H ; Go get it CMP AL, GRAPHICS_CUR_STOP ; Is this a 80x25 BW card MOV CX, MONO_CUR_DEF ; Set start/stop lines for cursor to 11/12 JE bd1 ; Yes it is 80x25 BW card, branch MOV CX, GRAPHICS_CUR_DEF ; No its not 80x25 card, start/stop lines are 6/7 bd1: MOV AH, SET_CURSOR_TYPE ; Set function call to set cursor type INT 10H ; Do it bd2: MOV CS:WORD PTR [inline_mod2+1],CX ; Save the cursor type setting in line POP DX POP CX POP BX MOV BX,DX ; DX points to offset of input buffer MOV AL,[BX] ; Get the number of characters in the buffer CMP AL,02H ; Is it bigger than 2 characters? JB sc_ret ; Nope, we have a problem here! DEC AL ; Now decrement AL to get number of real characters MOV AH, 00H ; buffer han hold. Zero out AH MOV CS:WORD PTR [inline_mod5+2],AX ; AX now contains the max number of chars that the buffer ; can hold. ADD BX,02H ; BX points to address at which to put first real character ; in input buffer ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; AUTOMATIC BUFFER TOGGLE (Why, I don't know) auto_buffer_toggle: ;; MOV BP,DS ;; Place the DS register into BP PUSH DS ;; Save the value of the DS register MOV DI,CS ;; Place the CS register into DI MOV DS,DI ;; and also into DS CMP BP,DI ;; Compare DS : CS values JB abt1 ;; If DS < CS then jump ;; inline_mod4: ;; CMP DI,0888H ;; Compare CS : AUX (this in-line address will be called AUXiliary) JE abt2 ;; If its equal (if we came this way last time!) then go swap JMP SHORT after_swap_loop ;; If so then avoid swaps ;; abt1: ;; MOV BP,DI ;; Set BP to highest register value (now determined to be CS) CMP DI,DS:WORD PTR [inline_mod4+2] ;; Compare CS : AUX JE after_swap_loop ;; If its not equal (if we came this way last time!) then go swap ;; abt2: ;; PUSH CS ;; Now we must swap the appropriate memory locations to allow the POP ES ;; editor to use the other buffer (There are two buffers that one ;; can transfer between depending on DS : CS relationship. MOV SI,offset last_entry ;; Load SI with starting address LEA DI,[SI+08H] ;; Load DI with second starting address MOV CX,0004H ;; 4 words are to be moved ... in order ... address of last string accessed, ;; address of highest available byte, base address of text holding buffer, ;; high address of holding buffer. ;; Values are initiallized to: ;; 1st buffer - 60h, 60h, 60h, 160h ;; 2nd buffer - 160h, 160h, 160h, 260h ;; swap_loop: ;; MOV AX,[DI] ;; Save the value in the secondary buffer MOVSW ;; Move the primary buffer value into the secondary buffer position MOV [SI-02H],AX ;; Replace emptied location with saved value LOOP swap_loop ;; Go back and swap next set of values ;; after_swap_loop: ;; MOV DS:WORD PTR [inline_mod4+2],BP ;; Load AUX such that AUX = Max(CS, DS) POP DS ;; Restore DS ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; MOV BP,000CH JMP SHORT rib1 reinit_buffer: MOV BP,0004H rib1: XOR SI,SI ; Zero out Source index MOV CS:WORD PTR [inline_mod3+1],SI ; Modify inline address just above XOR DI,DI ; Zero out Destination index MOV ES,DI ; Zero out the ES register AND BYTE PTR ES:[kbd_flag], INSERT_OFF_MASK ; Turn insert off start_read_char: AND BP,0FFFEH ; Turn off low bit in BP (Line may be shorter) CALL set_cursor ; Set the cursor shape as per mode XCHG AX,DX ; Save AX in DX MOV AH, INPUT_CHR_NOECHO ; Get a character from the keyboard INT 21H ; Call DOS for service CMP AL, ACK ; Is it an acknowledge character? JE start_read_char ; If so ... just forget it and go back MOV CX, offset start_read_char ; Save address of start_read_char label PUSH CX ; This is a return address for a nonexistent call! OR AL,AL ; Set up for test JNE normal_keyboard_chr ; Jump if non null character input extended_keyboard_chr: MOV AH, INPUT_CHR_NOECHO ; Null character, get ready to read next character INT 21H ; Get it PUSH ES ; Save ES PUSH CS ; Set ES to value in CS POP ES PUSH DI ; Save DI MOV CX,000FH ; Set counter to number of items in table 1 MOV DI, offset [table1] ; Set starting address of table 1 repnz SCASB ; Scan for occurrence of second character in table 1 POP DI ; Restore DI POP ES ; and ES XCHG CX,BX ; Let BX contain pointer to item found in table 1 ADD BX,BX ; Double it PUSH CS:WORD PTR [BX+table2] ; Index into table 2 for starting address of service code ; The value is pushed onto the stack to allow for the ; return (Without a corresponding call!) MOV BX,CX ; Restore original BX value RET ; Execute the fake return ;*************************************************************************** ; Individual service routines ;*************************************************************************** ;*********************************************************************************** Escape Key escape_handling: ; Escape character here CALL home_key ; Go to start of line CALL cntrl_end ; Delete to end restart_input: POP DI ; Pop the return address off of the stack JMP SHORT reinit_buffer ; Jump to reinitialize buffer and read normal_keyboard_chr: CMP AL, CNTL_BACKSPACE ; Control Backspace? JE nkc1 ; if so, go to backspace handling CMP AL, BACKSPACE ; Backspace? JNE nkc2 ; If not continue nkc1: JMP backspace_handling ; Backspace here, take care of it nkc2: CMP AL, CR ; Is it a carriage return? JNE nkc3 ; If not continue JMP cr_key ; Yes, go take care of it nkc3: CMP AL, ESC ; Is it an escape character JE escape_handling ; If so, go take care of it CMP AL, TAB ; Bad code here ** remove this ** JE nkc4 ; Bad code here ** remove this ** inline_mod5: nkc4: CMP DI,0888H ; Compare DI to max buffer size (modified in line in Begin_Dosed) JB printable_char ; If less than max then continue with printable character MOV AL, BELL ; Prepare to ring the bell JMP display_one_char ; Do it ;*********************************************************************************** Non editing character printable_char: AND BP,0FFF7H ; Turn off the no changes made flag OR BP,0002H ; Turn on the changes made to this line flag PUSH AX ; Save AX CALL display_and_test ; go display the character MOV DX,ES:[cursor_posn] ; Place the current cursor position in DX TEST BYTE PTR ES:[kbd_flag], INSERT_ON_MASK ; Is insert mode mask on? JE add_chr_to_inbuf ; If not then branch around shift up string PUSH DI ; Save the DI register shift_up: CMP DI,SI ; Are we pointing past the end? JBE end_shift_up ; Have we decended to the original point? MOV AL,[BX+DI-01H] ; Move this character in input buffer up MOV [BX+DI],AL ; one byte in memory DEC DI ; Next character down JMP SHORT shift_up ; Return for more end_shift_up: POP DI ; Restore original end of input buffer pointer INC DI ; Increment it by one INC SI ; Also increment the current character pointer CALL redisplay_line DEC SI ; Now decrement source so that it will look ; like normal overwrite to next code section add_chr_to_inbuf: POP AX ; Restore AX MOV AH,AL ; Move the current character into AH XCHG AL,[BX+SI] ; Put it into the input buffer INC SI ; Point to next character position CMP DI,SI ; Have we gone past the end JNB acti1 ; If not then forget update of DI MOV DI,SI ; DI is now reset to SI (which was >) acti1: AND AL,AH ; AND old character against new character CMP AL, BLANK ; If both are printable then we are finished ; because we have coundn't have shortened JNB acti_ret ; the line with the overwrite. (eg. A over ^E ; would shorten line by one character) TEST BYTE PTR ES:[kbd_flag], INSERT_ON_MASK ; If insert mode was on then we JNE acti_ret ; are finished also because we have already ; printed the string CMP SI,DI ; Also we can forget if we are at the end of the line JE acti_ret ; None of the above hold, and we may have trailing JMP note_shorter_change ; characters on the line that need to be blanked ; over. (caused by overwriting a ^x diagraph or a ; Tab character with a single character.) acti_ret: RET ;*********************************************************************************** End key end_key: TEST BP,0008H ; Have we made any changes to this buffer? JE move_to_end ; If so then go ahead an position to end of line. AND BP,0FFF7H ; No changes, lets now indicate that changes have been made, OR DI,DI ; and restore the input buffer. Start by checking DI for zero. JNE move_to_end ; Go restore if something is there. MOV AL,[BX-01H] ; Get the length of the string in the holding buffer. CMP [BX-02H],AL ; Is it larger than the max buffer size? JB recycle_input ; If so then we have problems and a restart is necessary. MOV AH,00H ; Zero out AH XCHG AX,DI ; Move the new length into DI CMP BYTE PTR [BX+DI], CR ; Is there a carriage return here JE move_to_end ; If so then go ahead and restore it recycle_input: JMP restart_input ; No, we must have garbage in the input buffer, go back and restart move_to_end: CALL right_arrow ; move over one character to the right JB move_to_end ; keep going if not at end error_return: RET ;*********************************************************************************** Control home key cntrl_home: PUSH SI ; Save the pointer into the input buffer CALL home_key ; Move to start of line POP SI ; Restore pointer MOV CX,DI ; Set CX to character count in string and remove the SUB CX,SI ; characters from start of line to current position from count. XOR DI,DI ; Clear out the DI register PUSH DI ; Save it. ** get rid of this ** PUSH CX ; and the new count of characters. JCXZ after_drop_down ; If the new count of characters is zero then nothing else to do. drop_text_down: MOV AL,[BX+SI] ; Get the current character INC SI ; Advance source pointer to next character MOV [BX+DI],AL ; Store it down into the next destination available INC DI ; Increment the destination pointer LOOP drop_text_down ; and continue for the count after_drop_down: POP DI ; Restore DI POP SI ; and SI ** change this to xor SI,SI ** JMP note_shorter_change ; Now go redisplay line on screen ;*********************************************************************************** Control end key cntrl_end: OR BP,0002H ; Turn on the change to line flag MOV CX,CS:WORD PTR [inline_mod3+1] ; Get the screen position of the last character in the screen blank_to_end: CMP CX,ES:[cursor_posn] ; Is the current screen position at the end of line? JBE after_blanking ; If so then jump CALL display_blank ; Display a blank JMP SHORT blank_to_end ; and continue until end of line position on screen is reached after_blanking: MOV DI,SI ; The new line length is current offset in the line JMP place_cursor ; and now place the cursor on the screen ;*********************************************************************************** Control right arrow cntrl_right_arrow: ; Move right to start of next word CALL right_arrow ; Move right one character JNB cra_ret ; If at the end then fall out of loop CALL check_non_by_alpha ; Check for non-alpha/alpha combination (return issued from subroutine ; if the condition is satisfied) JMP SHORT cntrl_right_arrow ; continue the cycle cra_ret: RET check_non_by_alpha: MOV AL,[BX+SI] ; Get character CALL check_alpha ; See if this is an alphabetic character JB cnba_ret ; If not then we are finished MOV AL,[BX+SI-01H] ; Get previous character CALL check_alpha ; Is this an alpha? JNB cnba_ret ; If so then we are still not happy and must continue searching. POP AX ; Pop off the fake return address if this location points ; to an alpha character and the previous one doesnt. cnba_ret: RET check_alpha: OR AL, LOWER_CASE_MASK ; Or in lower case bit CMP AL, SMALLA ; Is this the letter "a"? JB cnba_ret ; It is less than the letter "a" ... return CMP AL, LEFT_CURLY_BRACE ; Is this the character "{"? (one greater than "z") CMC ; Complement Carry flag so its on if < "{" RET ;*********************************************************************************** Right arrow right_arrow: CMP SI,DI ; Are we past the last character JNE redisplay_char ; If not then continue RET redisplay_char: MOV AL,[BX+SI] ; Move the current character into AL INC SI ; Bump the pointer #U8z]ge9^Z into input buffer CALL display_and_test ; Redisplay that character STC ; Set the carry flag RET ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; L0474: CALL right_arrow ;\ ;; JNB L0482 ; \ ;; MOV AL,07H ; \ This code is not called. ;; AND AL, BYTE PTR ES:[cursor_posn] ; / ;; JNE L0474 ; / ;; L0482: RET ;/ ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;*********************************************************************************** Control left arrow cntrl_left_arrow: CALL left_arrow ; Move left one character JB bt_ret ; Jump if we are at the end of the buffer CALL check_non_by_alpha ; See if we are at the start of an alph character string. JMP SHORT cntrl_left_arrow ; If not then loop (if we were then the return was issued from ; check_non_by_alpha) ;*********************************************************************************** Backtab key backtab: CALL left_arrow ; move left one character JB bt_ret ; If at the start of the line then quit MOV AL,07H ; set up the mask AND AL,DL ; check to see if we are on an 8 byte column. JNE backtab ; If not then continue left. bt_ret: RET ;*********************************************************************************** Left Arrow left_arrow: OR SI,SI ; Are we at the start of the line STC ; Set the carry flag JE cnba_ret ; If so then do nothing DEC SI ; Move the input buffer pointer back one CALL decrement_col_row ; Adjust the col row positon CMP BYTE PTR [BX+SI], TAB ; Have we just run over a tab? JE back_over_tab ; If so then go expand it CMP BYTE PTR [BX+SI], BLANK ; Compare for printable character JNB la_end ; If we have one then jump to final section CALL decrement_col_row ; Decrement col row one more time (for ^ character) JMP SHORT la_end ; Finish up ; Expand the tab character back_over_tab: PUSH SI ; Save the SI pointer into input buffer MOV CX,SI ; Set the count to its value MOV AL,CL ; and also AL MOV AH,07H ; JCXZ no_prev_tabs ; At start of line (no previous tab to align us) ; See if we can find another tab in front of us to ; align us on screen (character after that tab ; would be properly aligned on 8 byte boundary.) align: DEC SI ; Decrement the pointer into input buffer CMP BYTE PTR [BX+SI], BLANK ; Check for printable character JNB align_end ; If found cycle in loop CMP BYTE PTR [BX+SI], TAB ; Have we succeded in finding another tab? JE sub_prev_char_cnt ; If so then we know we are aligned so jump DEC AH ; No, this must be a control character diagraph (^x form) ; so we need to subract an additional character from the align_end: ; count of characters found so far. LOOP align ; Go back for more no_prev_tabs: ; Ok, we only get here if there were no previous ; characters in input buffer or if there were no previous ; tabs in the buffer SUB AH,CS:[start_off] ; Subtract out the screen bias position for location 0 of the ; input buffer pointer. sub_prev_char_cnt: SUB AH,AL ; These two statements remove the count of all previous characters ADD CL,AH ; in the buffer (either to tab boundary or start of line). ; Additional diagraph hats "^" have been previously subtracted ; from AH. AND CL,07H ; take modulo 8 JE end_jump_tab ; Did this tab expand into only one blank (remember we've already ; moved over one!), if so jump jump_tab: CALL decrement_col_row ; Calculate new column and row on screen LOOP jump_tab end_jump_tab: POP SI ; Restore input buffer pointer la_end: CLC ; Clear the carry flag JMP SHORT place_cursor ; Go place the cursor on the screen NOP ;*********************************************************************************** Home key home_key: ; home key service begins here CALL left_arrow ; move over one JB pc_ret ; jump if back at start JMP SHORT home_key ; Not there yet, keep going ;*********************************************************************************** Backspace key backspace_handling: ; backspace handling begins here CALL left_arrow ; first just move over one character JB pc_ret ; If we are already at the start of the line ; then we neednt continue ;*********************************************************************************** Delete Key del_key: ; Delete key handling begins here OR DI,DI ; Is the string length zero? JE pc_ret ; If so go to end CMP SI,DI ; Are we past the end of the string? JE pc_ret ; If so go to end PUSH SI ; Save the SI pointer to input buffer shift_down: CMP SI,DI ; Are we past the end: JE after_shift_down ; If so, finish up MOV AL,[BX+SI+01H] ; Get next character up MOV [BX+SI],AL ; then shift it down into this slot INC SI ; Increment the input buffer pointer JMP SHORT shift_down ; and cycle after_shift_down: POP SI ; Restore the input text buffer pointer DEC DI ; Decrement the length of the input buffer string note_shorter_change: OR BP,0003H ; Indicate that we have changed and potentially shortened the string. redisplay_line: AND BP,0FFF7H PUSH SI ; Save the pointer into the input buffer display_next_char: CMP SI,DI ; Are we past the end of the string? JNB after_display_char ; If so dont display MOV AL,[BX+SI] ; Get the character from the input buffer CALL display_and_test ; send it to the display INC SI ; update buffer pointer JMP SHORT display_next_char ; continue to end after_display_char: CALL set_cursor ; Set type of cursor, AX returns with current cursor location (end of line) TEST BP,0001H ; Is the old line longer? JE after_blank_pad ; If not then forget blanking the tail XCHG AX,CS:WORD PTR [inline_mod3+1] ; Put current cursor positon in end of line indicator and ; save that value for blanking operation XCHG AX,CX ; Put former end of line position in CX add_blank_pad: CALL display_blank ; Display a blank CMP CX,ES:[cursor_posn] ; Is current cursor position now at end of line JNBE add_blank_pad ; If not, then continue blanking loop. after_blank_pad: POP SI place_cursor: MOV AH, SET_CURSOR_POSN ; Load AH for Bios call PUSH BX ; Save BX and CX registers PUSH CX MOV CS:[current_col],DL ; Record current column position MOV BH,00H INT 10H ; Call bios for service POP CX ; Restore registers POP BX pc_ret: RET ;*********************************************************************************** Up Arrow up_arrow: ; Up arrow service starts here STD ; Set direction flag to decrement ;*********************************************************************************** Down Arrow down_arrow: ; Down arrow service starts here AND BP,0FFF7H CALL home_key ; Go to beginning of line CALL cntrl_end ; Delete to end of line da1: PUSH ES ; Save ES register PUSH DS ; Set ES to DS POP ES PUSH CS ; Set DS to CS POP DS MOV SI,DS:[last_entry] ; Get pointer to first byte of current string in ; input buffer (from text buffer) LODSB ; Obtain the character LEA DI,[BX-01H] ; Load DI with the offset of the length character ; of the input buffer MOV CX, TEXT_BUFFER_SIZE ; Set counter to look at each location in the text buffer search_for_len_byte: CALL get_char ; Get a character from the text holding buffer TEST AL, LENGTH_BYTE_MASK ; Is it a length byte? LOOPZ search_for_len_byte ; Nope, go back and try again CLD ; Yep, clear the direction flag JNE found_a_len_byte ; Jump if we found a length byte PUSH ES ; Restore DS POP DS POP ES ; Restore ES JMP restart_input found_a_len_byte: AND BP,0FFF1H ; Indicate new line from holding buffer, and no changes made to it. CALL get_char ; Get a dummy character to readjust the SI pointer TEST BYTE PTR [SI], LENGTH_BYTE_MASK ; Is next location a length byte JNE recover_string ; If so (then down arrow issued) jump to recover string DEC SI ; No, an up arrow was issued and we need to back SI down two bytes to ; set up for next get_char to be the length byte. CALL swap_and_get_tp ; Back a-one DEC SI CALL swap_and_get_tp ; and a-two recover_string: MOV DS:[last_entry],SI ; Load the address of the last accessed buffer string CALL get_char ; Get the length character from holding buffer AND AL, LENGTH_OFF_MASK ; Mask off the length byte identifier MOV AH, BYTE PTR ES:[DI-01H] ; Place Max buffer size in AH CMP AL,AH ; Is text string smaller than max buffer size? JB continue_recovery ; If so then continue recovery MOV AL,AH ; Uh-oh, take the max buffer size as the count of chars to restore continue_recovery: STOSB ; Save the length count CBW ; Get rid of high portion of AX XCHG AX,CX ; Place the count in CX PUSH CX ; and save it for later load_chr_and_display: CALL get_char ; Get a character from the holding buffer STOSB ; Store this character in the input buffer CALL display_and_test ; Display this character LOOP load_chr_and_display ; Continue until all characters are done POP DI ; Place the count of the number of characters in the ; string into DI MOV SI,DI ; Require the current pointer to be just past the end PUSH ES ; Restore DS POP DS POP ES ; Restore ES lcad_ret: RET ;*********************************************************************************** Control Page Down cntrl_page_down: TEST BP,0006H ; Are we on the original line or have we made mods JNE lcad_ret ; If so then do nothing PUSH DS ; Save some registers PUSH ES PUSH BX CALL home_key ; Move to start of line CALL cntrl_end ; Delete to the end of the line PUSH CS ; Set ES register to CS ** change to mov ** POP ES PUSH CS ; Set DS register to CS POP DS MOV DI,DS:[last_entry] ; Get address of last string accessed in holding buffer PUSH DI ; Save it. MOV SI,DI ; Point the source index to it. skip: CALL get_char ; Get a character from the text buffer CMP AL, CR ; Is it a carriage return? JNE skip ; If n~r~_ot keep going move_down: CMP SI,DS:[next_entry] ; Are we at the next available location in buffer JE pad_crs ; If so then break out of loop CALL get_char ; Get this character CALL save_char ; and move it down in the holding buffer. JMP SHORT move_down ; Continue the loop. pad_crs: MOV AL, CR ; Load AL with a carriage return MOV [DI],AL ; and into the buffer MOV BX,DI ; Now reset the base pointer one beyond last string in holding buffer. XCHG BX,DS:[next_entry] ; Put the old value in BX and the new value in place POP SI ; Restore the pointer to last string accessed continue_pad_cr: CMP BX,DI ; Are we at the old next_available slot yet? JE after_pad_cr ; If yes the break out CALL save_char ; No, save the carriage return JMP SHORT continue_pad_cr ; Keep going after_pad_cr: DEC SI ; Point to just before this entry (so Down arrow will pick it up) MOV DS:[last_entry],SI ; Save it as last accessed text entry POP BX ; Restore registers. POP ES POP DS JMP da1 ; Go perform a down arrow operation ;*********************************************************************************** Carriage Return cr_key: AND BYTE PTR ES:[kbd_flag], INSERT_OFF_MASK ; Turn off insert mode CALL set_cursor ; Change the cursor on the screen POP AX ; Pop the fake return address off the stack (so we really return) CALL move_to_end ; Move the cursor to the end of the line MOV AL, CR ; Move a CR into AL CALL display_one_char ; Display it MOV [BX+DI],AL ; Add the CR to the input buffer MOV AX,DI ; Move the length into AX MOV [BX-01H],AL ; Now move it into the length byte of the input buffer MOV SI,BX ; Point the Source index to the input buffer CMP AL,02H ; Are there at least two characters? ** remove this? ** JBE crk_ret ; If not then just forget the save PUSH CS ; Set ES to value in CS POP ES INC WORD PTR CS:[last_entry] ; Bump the pointer to the strings location in the text buffer TEST BP,0002H ; Have changes been made to this line? JE crk_ret ; If not then we are through MOV DI,CS:[next_entry] ; Point the destination to the next available slot OR AL, LENGTH_BYTE_MASK ; Add in the length byte bit mask save_string: CALL save_char ; Add it to the holding buffer CMP AL, CR ; Is this a carriage return? JE after_save_string ; If so, break out of loop LODSB ; Get the next character from the input buffer JMP SHORT save_string after_save_string: MOV CS:[next_entry],DI ; Save the new pointer to the text holding buffer omit_partial_string: CMP CS:[DI],AL ; Is it a carriage return? JE after_omit_partial ; If so we are finished CALL save_char ; No, that means there is a partial string here JMP SHORT omit_partial_string ; so fill with CRs until next CR is found after_omit_partial: MOV CS:[last_entry],DI crk_ret: RET get_char: ; Obtain a character from the text holding buffer CALL swap_and_get_tp ; First we must reverse SI and DI pointers LODS CS:[SI] ; Load the character from the text holding buffer into AL swap_and_get_tp: ; Reverse SI and DI pointers because XCHG SI,DI ; get_text_pointer assumes that DI indexes CALL get_text_pointer ; into the text holding buffer and not SI XCHG SI,DI ; Verify legal pointer into holding buffer RET save_char: ; Add a character to the text holding buffer CALL get_text_pointer ; Verify correctness of pointer STOSB ; Move the character in AL to the text holding buffer get_text_pointer: ; Obtain a legal pointer into the text holding buffer CMP DI,CS:[buffer_bot] ; Is the current pointer too small? JNB gtp1 ; If not, then continue MOV DI,CS:[buffer_top] ; Yes, set to upper limit DEC DI ; and decrement one gtp1: CMP DI,CS:[buffer_top] ; Is the current pointer too big? JB gtp_ret ; If not jump to end MOV DI,CS:[buffer_bot] ; Yes, set to lower limit gtp_ret: RET ;*********************************************************************************** Control Page Up cntrl_page_up: ; Control Page Up service begins here CALL home_key ; Go to start of line CALL cntrl_end ; And delete forward PUSH DS ; Save DS MOV AX,CS ; Set DS and ES to value in CS MOV DS,AX MOV ES,AX MOV DI,DS:[buffer_bot] ; Get base address of text buffer MOV DS:[last_entry],DI ; Set current pointer into text buffer to base MOV DS:[next_entry],DI ; Set next new pointer into text buffer to base MOV CX, TEXT_BUFFER_SIZE ; Set count to size of text holding buffer MOV AL, CR ; Set AL with CR and fill holding buffer repz STOSB ; with carriage returns POP DS ; Restore DS JMP restart_input ; Data area start_off db 0h current_col db 0h last_entry dw TEXT_BUFFER_START next_entry dw TEXT_BUFFER_START buffer_bot dw TEXT_BUFFER_START buffer_top dw TEXT_BUFFER_END aux_last dw AUX_BUFFER_START aux_next dw AUX_BUFFER_START aux_bot dw AUX_BUFFER_START aux_top dw AUX_BUFFER_END initialize: DOSED ENDP CSEG ENDS END DOSED