Category : Assembly Language Source Code
Archive   : DSKPATCH.ZIP
Filename : DISPATCH.ASM

;---------------------------------------------------------------------;
; DISPATCH.ASM Reads character entered and calls appropriate proc. ;
; 04-30-89*CV ;
;---------------------------------------------------------------------;

CGROUP GROUP CODE_SEG, DATA_SEG
ASSUME CS:CGROUP, DS:CGROUP

CODE_SEG SEGMENT PUBLIC

PUBLIC DISPATCHER
EXTRN READ_BYTE:NEAR, EDIT_BYTE:NEAR
EXTRN WRITE_PROMPT_LINE:NEAR
DATA_SEG SEGMENT PUBLIC
EXTRN EDITOR_PROMPT:BYTE
DATA_SEG ENDS
;---------------------------------------------------------------------;
;This is the central dispatcher. During normal editing and viewing, ;
;this procedure reads characters from the keyboard and, if the char ;
;is a command key (such as a cursor key), DISPATCHER calls the ;
;procedures that do the actual work. This dispatching is done for ;
;special keys listed in the table DISPATCH_TABLE, where the procedure ;
; addresses are stored just after the key names. ;
; If the character is not a special key, then it should be placed ;
;directly into the sector buffer--this is the editing mode. ;
; ;
;Uses: READ_BYTE, EDIT_BYTE, WRITE_PROMPT_LINE ;
;Reads: EDITOR_PROMPT ;
;---------------------------------------------------------------------;
DISPATCHER PROC NEAR
PUSH AX
PUSH BX
PUSH DX
DISPATCH_LOOP:
CALL READ_BYTE ;Read char into AX
OR AH,AH ;AX = 0 if no char read, -1
;for an extended code.
JZ NO_CHARS_READ ;No character read, try again
JZ DISPATCH_LOOP ;No char read, try again
JS SPECIAL_KEY ;Read extended code
MOV DL,AL
CALL EDIT_BYTE ;Was normal char, edit byte
JMP DISPATCH_LOOP ;Read another char
SPECIAL_KEY:
CMP AL,68 ;F10--exit?
JE END_DISPATCH ;Yes, leave
;Use BX to look through table
LEA BX,DISPATCH_TABLE
SPECIAL_LOOP:
CMP BYTE PTR [BX],0 ;End of table?
JE NOT_IN_TABLE ;Yes, key was not in table
CMP AL,[BX] ;Is it this table entry?
JE DISPATCH ;Yes, then dispatch
ADD BX,3 ;No, try next table entry
JMP SPECIAL_LOOP ;Check next table entry

DISPATCH:
INC BX ;Point to address of procedure
CALL WORD PTR [BX] ;Call procedure
JMP DISPATCH_LOOP ;Wait for another key

NOT_IN_TABLE: ;Do nothing, just read next char
JMP DISPATCH_LOOP

NO_CHARS_READ:
LEA DX,EDITOR_PROMPT
CALL WRITE_PROMPT_LINE ;Erase any invalid chars typed
JMP DISPATCH_LOOP ;Try again

END_DISPATCH:
POP DX
POP BX
POP AX
RET
DISPATCHER ENDP

CODE_SEG ENDS

DATA_SEG SEGMENT PUBLIC

CODE_SEG SEGMENT PUBLIC
EXTRN NEXT_SECTOR:NEAR ;In DISK_IO
EXTRN PREVIOUS_SECTOR:NEAR ;In DISK_IO
EXTRN PHANTOM_UP:NEAR, PHANTOM_DOWN:NEAR ;In phantom.asm
EXTRN PHANTOM_LEFT:NEAR, PHANTOM_RIGHT:NEAR
EXTRN WRITE_SECTOR:NEAR ;In DISK_IO.ASM
EXTRN UP_SECTOR_NO:NEAR ;In DISK_IO.ASM
EXTRN DOWN_SECTOR_NO:NEAR ;In DISK_IO.ASM
EXTRN A_DRIVE:NEAR, B_DRIVE:NEAR ;In DISK_IO.ASM
EXTRN D_DRIVE:NEAR ;In DISK_IO
CODE_SEG ENDS
;---------------------------------------------------------------------;
; This table contains the legal extended ASCII keys and the addresses ;
; of the procedures that should be called when each key is pressed. ;
; The format of the table is ;
; DB 72 ;Extended code for cursor up ;
; DW OFFSET CGROUP:PHANTOM_UP ;
;---------------------------------------------------------------------;
DISPATCH_TABLE LABEL BYTE
DB 59 ;F1
DW OFFSET CGROUP:PREVIOUS_SECTOR
DB 60 ;F2
DW OFFSET CGROUP:NEXT_SECTOR
DB 72 ;Cursor up
DW OFFSET CGROUP:PHANTOM_UP
DB 80 ;Cursor down
DW OFFSET CGROUP:PHANTOM_DOWN
DB 75 ;Cursor left
DW OFFSET CGROUP:PHANTOM_LEFT
DB 77 ;Cursor right
DW OFFSET CGROUP:PHANTOM_RIGHT
DB 88 ;Shift F5
DW OFFSET CGROUP:WRITE_SECTOR
DB 61 ;F3
DW OFFSET CGROUP:UP_SECTOR_NO
DB 62 ;F4
DW OFFSET CGROUP:DOWN_SECTOR_NO
DB 64 ;F6
DW OFFSET CGROUP:A_DRIVE
DB 65 ;F7
DW OFFSET CGROUP:B_DRIVE
DB 66 ;F8
DW OFFSET CGROUP:D_DRIVE
DB 0 ;End of table
DATA_SEG ENDS

END