begin working on itoa

Makefile

@@ -97,7 +97,7 @@ $(OBJ_DIR)/%.o: $(SRC_DIR)/%.s
 	$(AS) $(ASFLAGS) -o $@ $<
 	$(OBJCOPY) --remove-section .note.gnu.property $@
 
-MBR_TEST_OBJ		=	obj/mbr_test.o obj/serial.o
+MBR_TEST_OBJ		=	obj/mbr_test.o obj/serial.o obj/itoa.o
 
 mbr_test: $(MBR_TEST_OBJ) $(DISK)
 	$(LD) -T src/mbr_test.ld -o $(BIN_DIR)/mbr_test.bin $(MBR_TEST_OBJ)

src/itoa.s

@@ -0,0 +1,45 @@
+.section .text
+.code16
+
+.globl itoa
+
+.equ    ITOA_BUFFER_SIZE,   12
+
+# eax - number
+# ecx - base
+itoa:
+    push %bx
+    mov $numbers, %bx
+
+.debug:
+    jmp .debug
+
+    mov $(itoa_result + ITOA_BUFFER_SIZE - 1), %di
+    std
+.div:
+    divl %ecx
+    or %eax, %eax
+    jz .end         # we run out of numbers
+
+    # yep, we're using LUT for number -> character conversion since ASCII is a fuck
+    push %eax
+    add %bx, %ax
+    stosb
+    pop %eax
+
+    jmp .div
+.end:
+    cld
+
+    # we return ptr to string, since we're pushing chars in reverse, therefore
+    # beginning of string will change
+    mov %di, %ax
+
+    pop %bx
+    ret
+
+.section .bss
+.comm       itoa_result,        ITOA_BUFFER_SIZE
+
+.section .rodata
+numbers:    .ascii "0123456789ABCDEF"

src/mbr_test.s

@@ -29,11 +29,22 @@
     mov %ax, %ss
     xor %sp, %sp
 
+    # set ES segment
+    push %ds
+    pop %es
+
 .entry:
     call serial_init
 
     mov $msg, %si
     call prints
+
+    mov $12345678, %eax
+    mov $10, %ecx
+    call itoa
+
+    mov %ax, %si
+    call prints
 .halt:
     jmp .halt