convert.asm: Avoid stack usage for reversing string - use second buffer instead

src/convert.asm

@@ -2,6 +2,7 @@
 
 section .bss
 	cnvtBuff	resb	21
+	cnvtBuffRev	resb	21
 section .text
 	global	dec2str
 	global	udec2str
@@ -18,9 +19,10 @@ section .text
 ;	rsi*	Points to cnvtBuff for writing characters
 ;	r8*	Dividor for div
 dec2str:
-	lea	rsi, [rel cnvtBuff]
+	lea	rsi, [rel cnvtBuffRev]
 	test	rdi, rdi
 	jnz	.notZero
+	lea	rsi, [rel cnvtBuff]
 	mov	byte [rsi], '0'
 	mov	byte [rsi+1], EOS
 	jmp	.quit
@@ -38,20 +40,26 @@ dec2str:
 		mov	r8, 10
 		div	r8
 		add	rdx, '0'
-		push	rdx
+		mov	[rsi], dl
+		inc	rsi
 		inc	rcx
 		test	rax, rax
 		jnz	.convert
 		test	dil, dil
 		jz	.makeString
-	push	byte '-'
+	mov	[rsi], byte '-'
 	inc	rcx
+	inc	rsi
 	.makeString:
-		pop	rdx
-		mov	byte [rsi], dl
-		inc	rsi
-		loop	.makeString
-	mov	byte [rsi], EOS
+	lea	rdi, [rel cnvtBuff]
+	dec	rsi
+	.makeStringLoop:
+		mov	al, [rsi]
+		mov	[rdi], al
+		inc	rdi
+		dec	rsi
+		loop	.makeStringLoop
+	mov	byte [rdi], EOS
 
 	.quit:
 	lea	rax, [rel cnvtBuff]
@@ -68,9 +76,10 @@ dec2str:
 ;	rsi*	Points to cnvtBuff for writing characters
 ;	r8*	Dividor for div
 udec2str:
-	lea	rsi, [rel cnvtBuff]
+	lea	rsi, [rel cnvtBuffRev]
 	test	rdi, rdi
 	jnz	.notZero
+	lea	rsi, [rel cnvtBuff]
 	mov	byte [rsi], '0'
 	mov	byte [rsi+1], EOS
 	jmp	.quit
@@ -83,16 +92,20 @@ udec2str:
 		mov	r8, 10
 		div	r8
 		add	rdx, '0'
-		push	rdx
+		mov	[rsi], dl
+		inc	rsi
 		inc	rcx
 		test	rax, rax
 		jnz	.convert
-	.makeString:
-		pop	rdx
-		mov	byte [rsi], dl
-		inc	rsi
-		loop	.makeString
-	mov	byte [rsi], EOS
+	lea	rdi, [rel cnvtBuff]
+	dec	rsi
+	.makeStringLoop:
+		mov	al, [rsi]
+		mov	[rdi], al
+		inc	rdi
+		dec	rsi
+		loop	.makeStringLoop
+	mov	byte [rdi], EOS
 
 	.quit:
 	lea	rax, [rel cnvtBuff]
@@ -112,9 +125,10 @@ udec2str:
 ;	r11*	Amount to add to number (for ASCII conversion, lowercase or uppercase)
 hex2str:
 	mov	r9, rsi
-	lea	rsi, [rel cnvtBuff]
+	lea	rsi, [rel cnvtBuffRev]
 	test	rdi, rdi
 	jnz	.notZero
+	lea	rsi, [rel cnvtBuff]
 	mov	word [rsi], '0x'
 	mov	byte [rsi + 2], '0'
 	mov	byte [rsi + 3], EOS
@@ -141,19 +155,23 @@ hex2str:
 		.num:
 		add	rdx, '0'
 		.push:
-		push	rdx
+		mov	[rsi], dl
+		inc	rsi
 		inc	rcx
 		test	rax, rax
 		jnz	.convert
 
-	mov	word [rsi], '0x'
-	add	rsi, 2
+	mov	word [rsi], 'x0'
+	inc	rsi
+	add	rcx, 2
+	lea	rdi, [rel cnvtBuff]
 	.makeString:
-		pop	rdx
-		mov	byte [rsi], dl
-		inc	rsi
+		mov	al, [rsi]
+		mov	[rdi], al
+		inc	rdi
+		dec	rsi
 		loop	.makeString
-	mov	byte [rsi], EOS
+	mov	byte [rdi], EOS
 
 	.quit:
 	lea	rax, [rel cnvtBuff]