Category : Assembly Language Source Code
Archive   : NORTASM.ZIP
Filename : EDITOR.ASM

.MODEL SMALL

;-----------------------------------------------------------------------;
; This file contains procedures that are used for editing the SECTOR: ;
; ;
; WRITE_TO_MEMORY Write a byte into SECTOR ;
; EDIT_BYTE Change byte in memory and on screen ;
;-----------------------------------------------------------------------;

.CODE

.DATA
EXTRN SECTOR:BYTE
EXTRN SECTOR_OFFSET:WORD
EXTRN PHANTOM_CURSOR_X:BYTE
EXTRN PHANTOM_CURSOR_Y:BYTE
.CODE
;-----------------------------------------------------------------------;
; This procedure writes one byte to SECTOR, at the memory location ;
; pointed to by the phantom cursor. ;
; ;
; On entry: DL Byte to write to SECTOR ;
; ;
; The offset is calculated by ;
; OFFSET = SECTOR_OFFSET + (16 * PHANTOM_CURSOR_Y) + PHANTOM_CURSOR_X ;
; ;
; Reads: PHANTOM_CURSOR_X, PHANTOM_CURSOR_Y, SECTOR_OFFSET ;
; Writes: SECTOR ;
;-----------------------------------------------------------------------;
WRITE_TO_MEMORY PROC
PUSH AX
PUSH BX
PUSH CX
MOV BX,SECTOR_OFFSET
MOV AL,PHANTOM_CURSOR_Y
XOR AH,AH
MOV CL,4 ;Multiply PHANTOM_CURSOR_Y by 16
SHL AX,CL
ADD BX,AX ;BX = SECTOR_OFFSET + (16 * Y)
MOV AL,PHANTOM_CURSOR_X
XOR AH,AH
ADD BX,AX ;That's the address!
MOV SECTOR[BX],DL ;Now, store the byte
POP CX
POP BX
POP AX
RET
WRITE_TO_MEMORY ENDP

PUBLIC EDIT_BYTE
EXTRN SAVE_REAL_CURSOR:PROC, RESTORE_REAL_CURSOR:PROC
EXTRN MOV_TO_HEX_POSITION:PROC, MOV_TO_ASCII_POSITION:PROC
EXTRN WRITE_PHANTOM:PROC, WRITE_EDITOR_PROMPT:PROC
EXTRN CURSOR_RIGHT:PROC, WRITE_HEX:PROC, WRITE_CHAR:PROC
;-----------------------------------------------------------------------;
; This procedure changes a byte in memory and on the screen. ;
; ;
; DL Byte to write into SECTOR, and change on screen ;
; ;
; Uses: SAVE_REAL_CURSOR, RESTORE_REAL_CURSOR ;
; MOV_TO_HEX_POSITION, MOV_TO_ASCII_POSITION ;
; WRITE_PHANTOM, WRITE_PROMPT_LINE, CURSOR_RIGHT ;

; WRITE_HEX, WRITE_CHAR, WRITE_TO_MEMORY ;
; Reads: EDITOR_PROMPT ;
;-----------------------------------------------------------------------;
EDIT_BYTE PROC
PUSH DX
CALL SAVE_REAL_CURSOR
CALL MOV_TO_HEX_POSITION ;Move to the hex number in the
CALL CURSOR_RIGHT ; hex window
CALL WRITE_HEX ;Write the new number
CALL MOV_TO_ASCII_POSITION ;Move to the char. in the ASCII window
CALL WRITE_CHAR ;Write the new character
CALL RESTORE_REAL_CURSOR ;Move cursor back where it belongs
CALL WRITE_PHANTOM ;Rewrite the phantom cursor
CALL WRITE_TO_MEMORY ;Save this new byte in SECTOR
CALL WRITE_EDITOR_PROMPT ;Display the Edit prompt
POP DX
RET
EDIT_BYTE ENDP


END