From a4e81a265038b42acd27ef315d1796dd332c50e0 Mon Sep 17 00:00:00 2001
From: Christian Cunningham <cc@localhost>
Date: Sat, 13 Jul 2024 21:32:21 -0700
Subject: Strings

---
 zstring.inc | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 zstring.inc

(limited to 'zstring.inc')

diff --git a/zstring.inc b/zstring.inc
new file mode 100644
index 0000000..5c88c02
--- /dev/null
+++ b/zstring.inc
@@ -0,0 +1,57 @@
+%ifndef ZSTRING_INC
+%define ZSTRING_INC
+%ifndef SYS_INC
+%include "sys.inc"
+%endif
+%ifndef ALLOC_INC
+%include "alloc.inc"
+%endif
+
+%macro make_zstring 2-*
+%1:	db	%2
+	%rep %0-2
+	db %3
+	%rotate 1
+	%endrep
+	db 0
+%endm
+
+	section .text
+length_zstring:
+	;; rax = zstring address
+	push	rbp
+	mov	rbp,	rsp
+	;;
+	mov	rdx,	rax
+	xor	rax,	rax
+.loop:	
+	mov	cl,	byte [rdx]
+	cmp	cl,	0
+	je	.exit
+	inc	rax
+	inc	rdx
+	jmp	.loop
+.exit:
+	;;
+	mov	rsp,	rbp
+	pop	rbp
+	ret
+
+print_zstring:
+	;; rax = zstring address
+	push	rbp
+	mov	rbp,	rsp
+	;;
+	push	rax
+	mov	rsi,	rax
+	call	length_zstring
+	mov	rdx,	rax
+	mov	rax,	SYS_WRITE
+	mov	rdi,	1
+	syscall
+	;; 
+	mov	rsp,	rbp
+	pop	rbp
+	ret
+
+%endif
-- 
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