BASIC Interpreter from MikeOS is functioning

source/kernel/features/strings.asm

@@ -11,35 +11,176 @@
 os_compare_strings:	
 	cld
 
-.compare:
-    mov al, 0
-    scasb
-    je .di_ended
-    dec di
-	lodsb
-	scasb			; Compare di to si
-	jne .unequal		; If they are not equal, jump to .unequal
-	jmp .compare		; Finally, repeat
+	.compare:
+		mov al, 0
+		scasb
+		je .di_ended
+		dec di
+		lodsb
+		scasb			; Compare di to si
+		jne .unequal		; If they are not equal, jump to .unequal
+		jmp .compare		; Finally, repeat
 
-.unequal:
-	mov cl, 0		; Change to 0 if unquality is proven
-	ret
-.di_ended:
-   lodsb
-   cmp al, 20h ; 20h = space
-   je .equal
-   cmp al, 0
-   je .equal
-   jmp .unequal
-.equal:
-	mov cl, 1
+	.unequal:
+		mov cl, 0		; Change to 0 if unquality is proven
+		ret
+	.di_ended:
+	   lodsb
+	   cmp al, 20h ; 20h = space
+	   je .equal
+	   cmp al, 0
+	   je .equal
+	   jmp .unequal
+	.equal:
+		mov cl, 1
+		ret
+
+; ------------------------------------------------------------------
+; os_string_compare -- See if two strings match
+; IN: SI = string one, DI = string two
+; OUT: carry set if same, clear if different
+; from MikeOS kernel
+
+string_direct_compare:
+	pusha
+	.more:
+		mov al, [si]                    ; Retrieve string contents
+		mov bl, [di]
+		cmp al, bl                      ; Compare characters at current location
+		jne .not_same
+		cmp al, 0                       ; End of first string? Must also be end of second
+		je .end
+		inc si
+		inc di
+		jmp .more
+	.not_same:                              ; If unequal lengths with same beginning, the byte
+		popa                            ; comparison fails at shortest string terminator
+		clc                             ; Clear carry flag
+		ret
+	.end:                            ; Both strings terminated at the same position
+		popa
+		stc                             ; Set carry flag
+		ret
+
+
+; --------------------------------------------------------------------
+; Copies a string from si to di
+; IN:
+; si: points to first character of source string
+; OUT:
+; di: points to first character of destination string
+string_copy:
+	pusha
+	.loop:
+		; TODO could this cause issue when a character is > 1 byte?
+		lodsb   ; Load si character into ax and increment si by 1
+		stosb   ; Store ax in di location and increment di by 1
+		cmp ax, 0  ; if ax is a 0, quit
+		jne .loop
+	.done:
+		popa
+		ret
+
+; --------------------------------------------------------------------
+; Joins two strings together into a new string
+; IN/OUT:
+; ax: string1
+; bx: string2
+; cx: result string
+
+string_join:
+	pusha
+	.copy_string1:
+		mov si, ax
+		mov di, cx
+		call string_copy
+		mov ax, cx ; TODO check this bit
+		call string_length
+		add cx, ax
+	.copy_string2:
+		mov si, bx
+		mov di, dx
+		call string_copy
+	.done:
+		popa
+		ret
+
+; ------------------------------------------------------------------------
+; TODO
+string_cast_to_int:
 	ret
 
+; ------------------------------------------------------------------------
+
+; IN: AX = int
+; OUT: AX = string location (output buffer)
+string_cast_from_int: ; TODO I think this algorithm could be optimised
+	pusha
+	; Initialise base to decimal (base 10)
+	mov bx, 10
+	; clear the strigified int location
+	mov cx, 6
+	push ax
+	xor ax,ax
+	.clear_loop:
+		stosb
+		dec cx
+		cmp cx, 0
+		ja .clear_loop
+	; setup
+	pop ax
+	push ax
+	mov cx, -1
+	; loop over number to get the value of count (cx)
+	.count_loop:
+		xor dx,dx
+		div bx ; ax = ax // bx
+		inc cx
+		cmp ax, 0
+		ja .count_loop ; Jump if greater
+	pop ax
+	; loop over count downwards until count is 0
+	mov di, stringified_int
+	.stringify_loop:
+		mov cx,1 ;DEL
+		push cx
+		push bx
+		push ax
+		; Generate power of 10
+		mov ax, 1
+		mov cx,0 ;DEL
+		cmp cx, 1
+		jl .after_power_loop
+		.power_loop:
+			mul bx
+			dec cx
+			cmp cx, 0
+			ja .power_loop
+		.after_power_loop:
+		mov bx,ax
+		pop ax
+		pop cx
+		; ax = ax DIV bx
+		; dx = ax MOD bx
+		xor dx,dx
+		div bx
+		pop bx
+		add ax, 30h
+		stosb
+		mov ax, dx
+		dec cx
+		cmp cx, 0
+		ja .stringify_loop
+	.finish:
+		popa
+		;mov ax, stringified_int
+		ret
+
 ; Get the length of a string
 ; 'hello world', 0 is 11 characters long (excluding the terminator)
 ; input: si points to the string to be counted
 ; output: cl holds the length
-os_string_length:
+string_length:
    push si
    xor cl,cl ; Clear the al register
 .loop:
@@ -52,6 +193,8 @@ os_string_length:
    pop si
    ret
 
+
+
 ; convert a string to fat's filename format
 ; It will be capitalised and 11 characters long,
 ; 8 for the filename, 3 for the extension
@@ -60,8 +203,8 @@ os_string_length:
 ; output: di points to the fat formatted filename
 os_format_fat_filename:
    pusha
-   call os_upper_case
-   call os_string_length ; Stores the length of the string in cl
+   call string_upper_case
+   call string_length ; Stores the length of the string in cl
    xor ch,ch ; Clear ch to reset it to 0
    .character_loop:
 	  lodsb
@@ -147,7 +290,7 @@ string_unformat_fat_filename:
 ; Convert a string to all upper/lower case
 ; INPUT: si pointing to a string
 ; OUPUT: the same string in memory will now be capitalised/decapitalised
-os_upper_case: ; to upper case
+string_upper_case: ; to upper case
     pusha
     mov di, si
 .loop:
@@ -187,3 +330,9 @@ os_lower_case: ; to lower case
     popa
     ret
 
+string_lower_case:
+	ret
+string_input:
+	ret
+string_print_2hex:
+	ret