From 70ab8b19c37cb8f76f5133bda90c0264b6aa6838 Mon Sep 17 00:00:00 2001
From: Kwarde <kevin@kwarde.com>
Date: Tue, 15 Jul 2025 16:31:52 +0200
Subject: [PATCH] Allow printing prefixes for %x,%X,%b and %o (pass ~base to
 udec)

---
 src/console.asm | 26 ++++++++++++---
 src/convert.asm | 87 ++++++++++++++++++++++++++++++++++++++++++-------
 src/tests.asm   | 13 ++++++++
 3 files changed, 111 insertions(+), 15 deletions(-)

diff --git a/src/console.asm b/src/console.asm
index fe41669..701243e 100644
--- a/src/console.asm
+++ b/src/console.asm
@@ -70,8 +70,9 @@ puts:
 ;	%b	Unsigned integer, printed as binary number
 ;	%o	Unsigned integer, printed as octal number
 ;	%s	String
-;	%N*	Pad left, N chars (maximum 64). Supported specifiers: d, i, u, x, X, b, o
-;	*0N*	Pad left with zeroes, N chars (maximum 64). Supported specifiers: d, i, u, x, X, b, o
+;	%#{x}	Use prefix for printed number (non-decimal). Supported specifiers: x, X, b, o. Works in combination with width specifier (see below)
+;	%[#]n*	Pad left, n chars (maximum 64). Supported specifiers: d, i, u, x, X, b, o
+;	*[#]0n*	Pad left with zeroes, n chars (maximum 64). Supported specifiers: d, i, u, x, X, b, o
 ; <!> Unsupported specifiers are printed as-is
 ; <!> For all specifiers (except %%) an argument is expected. Mismatch between arguments given and specifiers provided will lead to issues
 ;
@@ -91,6 +92,8 @@ puts:
 ;	r12	Padding for numbers (0=nopadding, >0=padding w/ spaces, NOT >0=padding w/ zeroes)
 ;	r13	Padding: zeroes (=1) or spaces (=0)
 ;	r14	Keeps track of amount of processed format specifiers
+;	r15	Include prefix for specifiers (1=yes, 0=no)
+;<!>	TODO:	Keep r13 and r15 in one register (use bitmasking to determine whether to pad with zeroes or spaces and whether to include prefix)
 printf:
 	%macro load_arg 1
 	cmp	r14, 4
@@ -124,7 +127,13 @@ printf:
 		load_arg rsi
 		push_regs
 	mov	rdi, rsi
+	test	r15, r15
+	jz	%%baseNormal
+	mov	rsi, ~%1
+	jmp	%%args
+	%%baseNormal:
 	mov	rsi, %1
+	%%args:
 	mov	rdx, r12
 	mov	rcx, r13
 	mov	r8, %2
@@ -140,7 +149,7 @@ printf:
 	push	r12
 	push	r13
 	push	r14
-	sub	rsp, SIZE_QWORD
+	push	r15
 
 	cmp	byte [rdi], EOS
 	je	.emptyStr
@@ -156,6 +165,7 @@ printf:
 	xor	r10, r10
 	xor	r11, r11
 	xor	r14, r14
+	xor	r15, r15
 
 	.process:
 		cmp	byte [rdi], EOS
@@ -206,6 +216,14 @@ printf:
 		je	.wrapup
 		cmp	byte [rdi + 1], '%'
 		je	.rep_pct
+		; Include specifier (r15=1) or not (r15=0)
+		xor	r15, r15
+		cmp	byte [rdi + 1], '#'
+		jne	.argGetPadZeroes
+		inc	rdi
+		mov	r15, 1
+		; Padding: zeroes (r13=1) or spaces (r13=0)
+		.argGetPadZeroes:
 		xor	r13, r13
 		mov	r12, 1
 		cmp	byte [rdi + 1], '0'
@@ -384,7 +402,7 @@ printf:
 	xor	rax, rax
 
 	.quit:
-	add	rsp, SIZE_QWORD
+	pop	r15
 	pop	r14
 	pop	r13
 	pop	r12
diff --git a/src/convert.asm b/src/convert.asm
index bda7dc7..83d6fbd 100644
--- a/src/convert.asm
+++ b/src/convert.asm
@@ -30,8 +30,13 @@ itoa:
 	; Before doing anything, check if base is valid
 	cmp	rsi, 10
 	je	.ok
+
+	cmp	rsi, ~10
+	je	.negBase
 	xor	rax, rax
 	ret
+	.negBase:
+	not	rsi
 	.ok:
 	push	r12
 	push	r13
@@ -122,24 +127,54 @@ itoa:
 
 ;----- utoa(int, base, padLen, bool padZeroes, bool upperCase) -----;
 ; Converts an unsigned integer to a string
-; Return value: Pointer to converted string or 0(EOS) if entered base is invalid
+; Return value: Pointer to converted string or 0(EOS) if entered base is invalid.
+; <!> To use prefix (ie 0x, 0b or 0o), pass ~base instead of base
 ; Supported bases: 2 (binary), 8, (octal), 10 (decimal), 16 (hexadecimal)
 ; Used registers:
 ;	rax*	num to divide (DIV) >> Copy bytes when reversing string >> (ret) Pointer to converted string
 ;	rbx	Stores (upperCase)
-;	rdi*	(arg) Integer to convert
-;	rsi*	(arg) Base to convert to
-;	rdx*	(arg) Padding length >> modulo (DIV)
-;	rcx*	(arg) 0=pad spaces, otherwise pad zeroes >> Loop counter
-;	r8*	(arg) 0=lowercase letters (for bases using letters, ie 16), uppercase otherwise >> Stores character to copy to when determining number or uppercase/lowercase letter
+;	rdi*	(arg) Integer to convert >> base (positive) >> pointer to cnvtBuff[]
+;	*rsi	(arg) Base to convert to
+;	*rdx	(arg) Padding length >> modulo (DIV)
+;	*rcx	(arg) 0=pad spaces, otherwise pad zeroes >> Loop counter
+;	*r8	(arg) 0=lowercase letters (for bases using letters, ie 16), uppercase otherwise >> Stores padding character >> used for inserting prefix
 ;	r9*	Counts string length
 ;	r10*	Points to cnvtBuff(Rev)[]
-;	r11*	Remembers if number is negative (r11b)
+;	*r11	Stores padZeroes
 ;	r12	Stores (int)
 ;	r13	Stores (base)
 ;	r14	Stores (padLen)
 ;	r15	Stores (padZeroes)
 utoa:
+	%macro insert_prefix 0
+	xor	r8, r8
+	xor	rsi, rsi
+	
+	mov	r8, 'x0'
+	cmp	rdi, 16
+	cmove	rsi, r8
+	je	%%insert
+
+	mov	r8, 'o0'
+	cmp	rdi, 8
+	cmove	rsi, r8
+	je	%%insert
+
+	cmp	rdi, 2
+	jne	%%continue
+	mov	rsi, 'b0'
+
+	%%insert:
+	mov	word [r10], si
+	add	r10, 2
+	add	r9, 2
+	%%continue:
+	;nop
+	%endmacro		
+
+	;;
+	;; ENTRY
+	;;
 	; Before doing anything, check if base is valid
 	cmp	rsi, 2
 	je	.ok
@@ -149,8 +184,19 @@ utoa:
 	je	.ok
 	cmp	rsi, 16
 	je	.ok
+
+	cmp	rsi, ~16
+	je	.ok
+	cmp	rsi, ~10
+	je	.negBase
+	cmp	rsi, ~8
+	je	.ok
+	cmp	rsi, ~2
+	je	.ok
 	xor	rax, rax
 	ret
+	.negBase:
+	not	rsi
 	.ok:
 	push	rbx
 	push	r12
@@ -174,8 +220,13 @@ utoa:
 	mov	rdx, '0'
 	test	r15, r15
 	cmovnz	rdi, rdx
-	mov	r15, rdi
+	mov	r11, rdi
 	; Prepare for conversion
+	mov	rdi, r13
+	test	r13, r13
+	jns	.continuePrepare
+	not	rdi
+	.continuePrepare:
 	mov	rax, r12
 	xor	r9, r9
 	lea	r10, [rel cnvtBuffRev]
@@ -186,7 +237,7 @@ utoa:
 	mov	r8, 'A'-10
 	.convert:
 		xor	rdx, rdx
-		div	r13
+		div	rdi
 		cmp	dl, 9
 		jle	.noLetter
 		add	dl, r8b
@@ -199,17 +250,31 @@ utoa:
 		inc	r9
 		test	rax, rax
 		jnz	.convert
+	; Insert prefix if needed
+	test	r13, r13 ;prefix needed? (MSB not set)
+	jns	.checkPadding
+	test	r15, r15 ;prefix now? (padding with spaces; r15 is zero)
+	jnz	.checkPadding
+		insert_prefix
+	
 	.checkPadding:
 	; Substract length of converted number from padLen
 	sub	r14, r9
 	cmp	r14, 0
-	jle	.makeString
+	jle	.checkPrefix
 	mov	rcx, r14
 	.addPadding:
-		mov	byte [r10], r15b
+		mov	byte [r10], r11b
 		inc	r10
 		inc	r9
 		loop	.addPadding
+	; Insert prefix if needed
+	.checkPrefix:
+	test	r13, r13 ;prefix needed? (MSB not set)
+	jns	.makeString
+	test	r15, r15 ;prefix now? (padding with zeroes; r15 is not zero)
+	jz	.makeString
+		insert_prefix
 	.makeString:
 	dec	r10 ;don't point to past last character
 	lea	rdi, [rel cnvtBuff]
diff --git a/src/tests.asm b/src/tests.asm
index e32c26d..daf35a6 100644
--- a/src/tests.asm
+++ b/src/tests.asm
@@ -99,6 +99,8 @@ section .rodata
 	printf12Str		db	"\nRAX\t%064b\nEAX\t\t\t\t\t%032b\n AX\t\t\t\t\t\t\t%016b\n AH\t\t\t\t\t\t\t%08b\t\n AL\t\t\t\t\t\t\t\t%08b\n",EOS
 	printf13		db	TAB,"printf(",DQUO,"%o | %8o | %08o\n",DQUO,", 1500, 1500, 1500): ",NL,TAB,TAB,EOS
 	printf13Str		db	"%o | %8o | %08o\n",EOS
+	printf14		db	TAB,"printf(",DQUO,"%#b | %#08b | %#x | %#8X\n | %#o",DQUO,", 8, 8, 0xABCDEF, 0x12345678, 15): ",NL,TAB,TAB,EOS
+	printf14Str		db	"%#b | %#08b | %#x | %#8X | %#o\n",EOS
 
 	; strlen()
 	msgStrlen		db	NL,"TEST strlen()",NL,EOS
@@ -383,6 +385,17 @@ _start:
 	mov	rdx, 1500
 	mov	rcx, 1500
 	call	printf
+
+	; TEST 14
+	lea	rdi, [rel printf14]
+	call	print
+	lea	rdi, [rel printf14Str]
+	mov	rsi, 8
+	mov	rdx, 8
+	mov	rcx, 0xABCDEF
+	mov	r8, 0x12345678
+	mov	r9, 15
+	call	printf
 %endif
 
 ;---