Adds atoi

src/convert.asm

@@ -6,9 +6,154 @@ section .bss
 	cnvtBuff	resb	67
 	cnvtBuffRev	resb	67
 section .text
+	global	atoi
 	global	itoa
 	global	utoa
 
+;----- atoi(*str[]) -----;
+; Converts numeric string to an integer
+; Return value: Converted integer or 0 if input was invalid
+; Used registers:
+;	rax*	(ret)
+;	rdi*	(arg) Numeric string to convert
+;	rsi*	Stores base
+;	rdx*	Stores max usable ascii number
+;	rcx*	Loop counter
+;	r8*	tmp storage rsi (cmov) >> Loop counter for calculating base^n
+;	r9*	tmp storage rdx (cmov) >> Calculated base^n
+;	r10*	Stores return value (since RAX is used by IMUL)
+atoi:
+	xor	rax, rax
+	xor	rcx, rcx
+	xor	r10, r10
+	cmp	byte [rdi], EOS
+	je	.quit
+
+	; -- Test if negative (increase pointer to str, result is always calculated positively. Once reaching '-' again, then NEG)
+	cmp	byte [rdi], '-'
+	jne	.noMinusSign
+	inc	rdi
+	inc	rcx ;make sure .calculateLoop includes minus sign
+
+	; -- Determine base
+	.noMinusSign:
+	; hex?
+	mov	r8, 16
+	cmp	word [rdi], '0x'
+	cmove	rsi, r8
+	je	.skipBaseNotation
+	; octal?
+	mov	r8, 8
+	mov	r9, '7'
+	cmp	word [rdi], '0o'
+	cmove	rsi, r8
+	cmove	rdx, r9
+	je	.skipBaseNotation
+	; binary?
+	mov	r8, 2
+	mov	r9, '1'
+	cmp	word [rdi], '0b'
+	cmove	rsi, r8
+	cmove	rdx, r9
+	je	.skipBaseNotation
+	; nope, decimal
+	mov	rsi, 10
+	mov	rdx, '9'
+	jmp	.getLen
+	.skipBaseNotation:
+	cmp	rcx, 1 ;If '-' was found, using base is invalid
+	je	.quit
+	add	rdi, 2
+
+	; -- Get length of numeric string + test if valid
+	.getLen:
+	.getLenLoop:
+		cmp	byte [rdi], EOS
+		je	.calculate
+		cmp	byte [rdi], '0'
+		jb	.quit
+		; Test if valid
+		cmp	rsi, 16
+		je	.getLenLoop_testHex
+		cmp	byte [rdi], dl
+		ja	.quit
+		jmp	.getLenLoop_cnt
+		.getLenLoop_testHex:
+		cmp	byte [rdi], 'F'
+		ja	.quit
+		cmp	byte [rdi], 'A'
+		jb	.testHex_isNum
+		jmp	.getLenLoop_cnt
+		.testHex_isNum:
+		cmp	byte [rdi], '9'
+		ja	.quit
+		
+		.getLenLoop_cnt:
+		inc	rdi
+		inc	rcx
+		jmp	.getLenLoop
+
+	; -- Calculate the number
+	.calculate:
+	dec	rdi ;don't point to EOS
+	xor	r8, r8
+
+	.calculateLoop:
+		cmp	byte [rdi], '-'
+		je	.wrapup_neg
+		; Calculate base^n
+		.calcBase:
+			test	r8, r8
+			jz	.calcBase_firstLoop
+			cmp	r8, 1
+			je	.calcBase_secondLoop
+			jmp	.calcBase_otherLoops
+
+			.calcBase_firstLoop:
+			mov	r9, 1
+			jmp	.calcNum
+			.calcBase_secondLoop:
+			mov	r9, rsi
+			jmp	.calcNum
+			.calcBase_otherLoops:
+			mov	rax, rsi
+			mov	r9, r8
+			dec	r9
+			.calcBaseLoop:
+				imul	rsi
+				dec	r9
+				test	r9, r9
+				jnz	.calcBaseLoop
+			mov	r9, rax
+
+		; Calculate number
+		.calcNum:
+		xor	rax, rax
+		mov	al, byte [rdi]
+		cmp	al, 'A'
+		jb	.calcNum_notHex
+		sub	al, 55 ;'A'-10 (65-10)
+		jmp	.calcNum_cnt
+		.calcNum_notHex:
+		sub	al, '0'
+
+		.calcNum_cnt:
+		imul	r9
+
+		add	r10, rax
+		dec	rdi
+		inc	r8
+		loop	.calculateLoop
+
+	jmp	.quit
+
+	.wrapup_neg:
+	neg	r10
+
+	.quit:
+	mov	rax, r10
+	ret
+
 ;----- itoa(int, base, padLen, bool padZeroes) -----;
 ; Converts a signed integer to a string
 ; Return value: Pointer to converted string or 0(EOS) if entered base is invalid