Added a HEX editor

src/filetable.asm

@@ -17,6 +17,6 @@ filetable:
     db 'filetable',0,      'txt',0,2,1   ; filetable.txt - start: 2, size: 1
     db 'kernel',0,0,0,0,   'bin',0,3,3   ; kernel.bin    - start: 3, size: 3
     db 'calc',0,0,0,0,0,0, 'bin',0,6,1   ; calc.bin      - start: 6, size: 1
-    db 'edit',0,0,0,0,0,0, 'bin',0,7,1   ; edit.bin      - start: 6, size: 1
+    db 'edit',0,0,0,0,0,0, 'bin',0,7,2   ; edit.bin      - start: 6, size: 2
 
 times 512-($-$$) db 0

src/fs/edit.asm

@@ -0,0 +1,101 @@
+[bits 16]
+
+launch:
+    call resetTextMode
+    mov si, headerMsg
+    call print
+    xor cx, cx
+    mov di, hexCode
+
+getHexCh:
+    xor ax, ax
+    int 0x16
+    cmp al, '$'     ; Check for end of input (Denoted by a "$")
+    je .runInput
+    cmp al, '!'     ; End editor, Exit back to kernel
+    je return
+    cmp al, 0x08    ; Backspace
+    je .backspace
+
+    xor ah, ah
+    call asciiToHex ; Get the hex digit into bx
+
+    cmp ax, 15      ; Check if it's a hex character
+    jg getHexCh     ; If not, ignore it
+
+    inc cx
+    cmp cx, 2       ; Check if we've gotten a whole byte (2 hex digits/nibbles)
+    je .putByte
+    mov [hexByte], al
+    jmp getHexCh
+.putByte:
+    cmp di, hexCode+256 
+    jge getHexCh    ; Max length reached
+    rol byte [hexByte], 4
+    or byte [hexByte], al
+    mov al, [hexByte]
+    mov [di], al
+    mov dx, [hexByte]
+    call printHexByte
+    inc di
+    xor cx, cx
+    mov al, ' '
+    mov ah, 0x0e
+    int 0x10
+    jmp getHexCh
+.backspace:
+    mov byte [hexByte], 0
+    xor cx, cx
+    cmp di, hexByte     ; Check if there's anything to delete
+    je getHexCh         ; If not, ignore
+    mov byte [di], 0
+    dec di
+    mov si, backChars
+    call print
+    jmp getHexCh
+.runInput:
+    mov si, runMsg
+    call print
+    call hexBegin       ; Call the code
+    jmp launch
+
+; Expects al to contain an ASCII character, will set bx to it's hex equivalent
+asciiToHex:
+    cmp al, '9'
+    jle .getHex
+    sub al, 7
+.getHex:
+    sub al, '0'
+    ret
+
+return:
+    mov ax, 0x2000
+    mov ds, ax
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+    mov ss, ax
+
+    jmp 0x2000:0x0000
+
+; - Includes -
+%include "./src/lib/screen.asm"
+%include "./src/lib/print.asm"
+; ------------
+
+headerMsg: db   " - EDITOR - ", ENDL, \
+                "Type '$' to run your code or '!' to exit", ENDL, ENDL, 0
+runMsg: db ENDL, " -- Executing -- ", ENDL, ENDL, 0
+
+backChars: db 8, 8, 8, '  ', 8, 8, 0
+
+hexByte: db 0
+
+hexBegin: ; The label we jump to
+    pusha
+hexCode: times 256 db 0     ; Code buffer (user input code)
+hexEnd: 
+    popa
+    ret
+
+times 2*512-($-$$) db 0