Added lowercase function, string length function formating to fat12

function

source/kernel/features/strings.asm

@@ -25,24 +25,95 @@ os_compare_strings:
 	mov cl, 1
 	ret
 
-
-; Convert a string to all upper case
-os_upper_case:
-    pusha
-    mov di, si
-.loop:
+; 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:
+   push si
+   xor cl,cl ; Clear the al register
+.loop
    lodsb
-    inc di
    cmp al, 0
    je .finish
-    cmp al, 7Ah
-    jns .loop
-    cmp al, 61h
-    js .loop
-    sub al, 20h
-    dec di
-    stosb
+   inc cl
    jmp .loop
+.finish
+   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
+; eg: 'file.txt' -> 'FILE    TXT'
+; input: si points to filename, di points to a free 11 bytes in memory
+; 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
+   mov bl, 11
+   sub bl, cl ; 11 - string_length
+   .character_loop:
+	  lodsb
+	  cmp al, 0
+	  je .finish
+	  cmp al, 2Eh ; 2Eh
+	  je .add_spaces ; This will end up back at .character_loop
+	  stosb
+	  jmp .character_loop
+
+   .add_spaces: ; Add the number of spaces as bl holds
+	  mov al, ' ' ; 20h = space
+	  .spaces_loop:
+		 stosb
+		 cmp bl, 0
+		 je .character_loop
+		 dec bl
+		 jmp .spaces_loop
+   .finish:
+	  popa
+	  ret
+
+; 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:
+    pusha
+    mov di, si
+.loop:
+    lodsb ; Load the character into al
+    inc di
+    cmp al, 0
+    je .finish ; If it's null then the string is finished
+    cmp al, 7Ah ; 7Ah = 'z'
+    jns .loop ; Ignore if it's more than 'z'
+    cmp al, 61h ; 61h = 'a'
+    js .loop ; Ignore if it's less than 'a'
+    sub al, 20h ; Otherwise subtract 20h to capitalise it
+    dec di
+    stosb ; Store the new value
+    jmp .loop ; Next character
+.finish:
+    popa
+    ret
+
+os_lower_case:
+    pusha
+    mov di, si
+.loop:
+    lodsb ; Load the character into al
+    inc di
+    cmp al, 0
+    je .finish ; If it's null then the string is finished
+    cmp al, 5Ah ; 5Ah = 'Z'
+    jns .loop ; Ignore if it's more than 'Z'
+    cmp al, 41h ; 41h = 'A'
+    js .loop ; Ignore if it's less than 'A'
+    add al, 20h ; Otherwise subtract 20h to capitalise it
+    dec di
+    stosb ; Store the new value
+    jmp .loop ; Next character
 .finish:
     popa
     ret

source/kernel/games/snake.asm

@@ -1,94 +0,0 @@
-game_snake:
-   call .draw_screen
-   call .detect_input
-
-.draw_screen:
-   call os_set_graphics_mode ; Clear screen
-.draw_snake_loop:
-   mov ax, [snake_x]
-   mov [x_start], ax
-   mov [x_end], ax
-
-   mov bx, [snake_y]
-   mov [y_start], bx
-   mov [y_end], bx
-
-   call os_draw_graphical_rectangle
-   ret
-
-; Player 1 movements
-.up:
-   mov dword [snake_direction], 0
-   jmp .end_detect_input
-.down:
-   mov dword [snake_direction], 2
-   jmp .end_detect_input
-.left:
-   mov dword [snake_direction], 3
-   jmp .end_detect_input
-.right:
-   mov dword [snake_direction], 1
-   jmp .end_detect_input
-
-.move_up:
-   mov dx, [snake_y]
-   sub dx, 1
-   mov [snake_y], dx
-   ret
-.move_down:
-   mov dx, [snake_y]
-   add dx, 1
-   mov [snake_y], dx
-   ret
-.move_left:
-   mov dx, [snake_x]
-   sub dx, 1
-   mov [snake_x], dx
-   ret
-.move_right:
-   mov dx, [snake_x]
-   add dx, 1
-   mov [snake_x], dx
-   ret
-
-.move_snake:
-   cmp dword [snake_direction], 0
-   je .move_up
-   cmp dword [snake_direction], 1
-   je .move_right
-   cmp dword [snake_direction], 2
-   je .move_down
-   ; Else it must be left
-   jmp .move_left
-
-
-.detect_input:
-   call os_read_input
-   cmp al, 08h
-   je .finish
-
-   ; Player 1
-   cmp al, 77h       ; Pressed 'w' up
-   je .up
-   cmp al, 61h       ; Pressed 'a' left
-   je .left
-   cmp al, 73h       ; Pressed 's' down
-   je .down
-   cmp al, 64h       ; Pressed 'd' right
-   je .right
-.end_detect_input:
-   call .move_snake
-   call .draw_screen
-
-   jmp .detect_input
-
-.finish:
-   call os_set_text_mode
-   call os_start_cli
-
-
-section .data:
-   snake_x: dw 5
-   snake_y: dw 5
-   snake_direction: dw 1 ; 0=up, 1=right, 2=down, 3=left
-   snake_length: dw 1

source/kernel/kernel.asm

@@ -2,21 +2,28 @@ ORG 0h
 BITS 16
 
 start:
-   mov si, boot_message
-   call os_upper_case
    mov si, boot_message
    call os_print_string_nl
 
    mov si, help_text
    call os_print_string_nl
 
+   mov si, file_name
+   call os_print_string_nl
+   mov di, fat_file_name
+   call os_format_fat_filename
+   mov si, fat_file_name
+   call os_print_string_nl
+
    call os_start_cli
    hlt
 
 halt:
    jmp halt
 
-boot_message: db 'kernel successfully loaded!', 0
+boot_message: db 'OK] Kernel successfully loaded!', 0
+file_name: db 'hello.cws', 0
+fat_file_name: db '           ',0 ; 11 characters
 
 ; ------------------------------------------------------------------
 ; FEATURES -- Code to pull into the kernel
@@ -29,4 +36,3 @@ boot_message: db 'kernel successfully loaded!', 0
     %INCLUDE "source/kernel/features/utils.asm"
 ; GAMES -- Games that I wrote for it
 	%INCLUDE "source/kernel/games/pong.asm"
-	%INCLUDE "source/kernel/games/snake.asm"