Integer division and square root

src/errno.asm

@@ -16,12 +16,15 @@
 ;       ; handle error
 
 pub const OK                   = 0x0000
+
 pub const SCREEN_INVALID_MODE  = 0x0001
 pub const SCREEN_INVALID_WIDTH = 0x0003
 pub const SCREEN_FB_TOO_SMALL  = 0x0005
 pub const SCREEN_OUTSIDE_FB    = 0x0007
 
+pub const DIV_BY_ZERO = 0x01001
+
 pub const MAGIC_BAD            = 0x8001
 
 ; Extended error codes, these would require loading a 32 bit value.
-pub const EXT_OK              = 0x00000000
+pub const EXT_OK              = 0x00000000

src/imath.asm

@@ -1,3 +1,82 @@
+include errno
+
+; (uint32_t, uint32_t) div(uint32_t, uint32_t);
+;   Divides two integers.
+;
+; Arguments:
+; - r1: Dividend
+; - r2: Divisor
+; Results:
+; - r1: Quotient
+; - r2: Remainder
+; Errors:
+; - `ERR_DIV_BY_ZERO`: The divisor was `0`.
+;
+pub div:
+    cmp r2, 0
+    je _div__by_0
+    mov r4, r2
+    mov r2, r1
+    mov r3, 1
+    cmp r1, 0
+    jge _div__loop
+    mov r1, 1
+    lsl r1, r1, 31
+_div__loop:
+    lsl r4, r4, 1
+    lsl r3, r3, 1
+_div__loop_entry:
+    cmp r4, r1
+    jb _div__loop
+    mov r1, 0
+_div__loop2:
+    cmp r2, r4
+    jb _div__loop2_no
+    sub r2, r2, r4
+    add r1, r1, r3
+_div__loop2_no:
+    lsr r4, r4, 1
+    lsr r3, r3, 1
+    cmp r3, 0
+    jne _div__loop2
+    mov flags, errno.OK
+    jmp r13
+_div__by_0:
+    mov flags, errno.DIV_BY_ZERO
+    jmp r13
+
+; uint32_t sqrt(uint32_t);
+; Calculates the integer square root.
+;
+; Arguments:
+; - r1: The unsigned 32 bit value to take the square root of.
+; Results:
+; - r1: The square root of the input, rounded down.
+; Clobbers:
+; - r1 - r6
+;
+pub sqrt:
+	mov r2, 0
+	mov r3, 16
+	mov r4, 0
+	lsl r5, r3, 12
+_sqrt__loop:
+	lsl r6, r2, r3
+	sub r3, r3, 1
+	lsr r5, r5, 1
+	lsl flags, r5, r3
+	add r6, r6, flags
+	add r6, r6, r4
+	cmp r6, r1
+	ja _sqrt__test
+	or r2, r2, r5
+	mov r4, r6
+_sqrt__test:
+	cmp r3, 0
+	jne _sqrt__loop
+	mov r1, r2
+	jmp r13
+
 ; Multiplies r1 and r2, returning the lower part of the result
 ; Arguments:
 ; r1 - The first value
@@ -111,4 +190,4 @@ pub max: ; SHOULD BE INLINED
 	and r2, r2, flags
 	; return x ^ ((x ^ y) & -(x < y))
 	xor r1, r1, r2
-	jmp r13
+	jmp r13