From dcb2b8acaea050465b0d91e86c802d197576d49f Mon Sep 17 00:00:00 2001
From: Kwarde <kevin@kwarde.com>
Date: Wed, 25 Jun 2025 11:08:56 +0200
Subject: [PATCH] Start writing printf() D:

---
 console.asm | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 113 insertions(+), 1 deletion(-)

diff --git a/console.asm b/console.asm
index 2d82cec..8665205 100644
--- a/console.asm
+++ b/console.asm
@@ -1,11 +1,15 @@
 extern	NR_write
 extern	strlen
+extern	strcat
 
 section .rodata
-	NL	db	0xA
+	NL		db	0xA
+section .bss
+	printfBuff	resb	4096
 section .text
 	global	print
 	global	puts
+	global	printf
 
 ;----- print (char* string) -----;
 ; return value: N/A
@@ -37,5 +41,113 @@ puts:
 	mov	rdx, 1
 	syscall
 
+	leave
+	ret
+;----- printf(const char* string, ...) -----;
+printf:
+	push	rbp
+	mov	rbp, rsp
+
+	push	r12
+	push	r13
+	;sub	rsp, 8
+
+	xor	r10, r10
+	lea	r11, [rel printfBuff]
+	.makeStr:
+		cmp	byte [rdi], 0
+		je	.finish
+		cmp	byte [rdi], '%'
+		je	.repArg
+		mov	r12b, byte [rdi]
+		mov	byte [r11], r12b
+		jmp	.continue
+		.repArg:
+			cmp	byte [rdi+1], 0
+			je	.finish
+			cmp	byte [rdi+1], 'd'
+			je	.rep_d
+			cmp	byte [rdi+1], 's'
+			je	.rep_s
+
+			.rep_d:
+			;mov	byte [r11], 'D' ;%d => Dd
+			;push	rdi
+			cmp	r10, 0
+			je	.rep_d_rsi
+			cmp	r10, 1
+			je	.rep_d_rdx
+			cmp	r10, 2
+			je	.rep_d_rcx
+			cmp	r10, 3
+			je	.rep_d_r8
+			cmp	r10, 4
+			je	.rep_d_r9
+
+			;get from stack
+
+			.rep_d_rsi:
+			.rep_d_rdx:
+			.rep_d_rcx:
+			.rep_d_r8:
+			.rep_d_r9:
+
+			inc	r10
+			jmp	.continue
+
+			.rep_s:
+			;mov	byte [r11], 's' ;%s => Ss
+			cmp	r10, 0
+			je	.startInsert
+			cmp	r10, 1
+			je	.rep_s_rdx
+			cmp	r10, 2
+			je	.rep_s_rcx
+			cmp	r10, 3
+			je	.rep_s_r8
+			cmp	r10, 4
+			je	.rep_s_r9
+
+			push	rdi
+			sub	rsp, 8
+			lea	rdi, [rel printfBuff]
+
+			;get from stack
+			mov	rsi, qword [rbp + r10*8]
+
+			.rep_s_rdx:
+			mov	rsi, rdx
+			jmp	.startInsert
+			.rep_s_rcx:
+			mov	rsi, rcx
+			jmp	.startInsert
+			.rep_s_r8:
+			mov	rsi, r8
+			jmp	.startInsert
+			.rep_s_r9:
+			mov	rsi, r9
+
+			.startInsert:
+			mov	rdi, rsi
+			call	strlen
+			mov	r13, rax
+			call	strcat
+			add	r11, r13
+			add	r10, 2 ;skip '%' and 'd/s'
+			add	rsp, 8
+			pop	rdi
+		.continue:
+		inc	rdi
+		inc	r11
+		jmp	.makeStr
+	.finish:
+	mov	byte [r11+1], 0x0
+	lea	rdi, [rel printfBuff]
+	call	print
+
+	;add	rsp, 8
+	pop	r13
+	pop	r12
+
 	leave
 	ret