Adds strcpy()

src/string.asm

@@ -2,6 +2,7 @@
 
 section .text
 	global	strlen
+	global	strcpy
 
 ;----- strlen(*str[]) -----;
 ; Gets the length of given string
@@ -19,3 +20,35 @@ strlen:
 	not	rax
 	dec	rax
 	ret
+
+;----- strcpy(*dest[], *src[], maxLength) -----;
+; Copies one string (src) into the other (dest), overwriting dest
+; NOTE: maxLength must never exceed size of dest[]. 
+; Return value: Pointer to dest
+; Used registers:
+;	rax*	(ret) Pointer to dest[]
+;	rdi	(arg) Pointer to dest[]
+;	rsi	(arg) Pointer to src[]
+;	rdx	(arg) Max amount of characters to copy / size of dest[] <!>Must never be greater than size of dest[]!
+;	rcx*	Counter for movsb
+;	r8*	Backup for rdi
+strcpy:
+	mov	r8, rdi
+	mov	rdi, rsi
+	call	strlen
+	mov	rcx, rdx
+	cmp	rcx, rax
+	je	.decMaxLen ;rcx-1 for EOS
+	ja	.setMaxLen ;set rcx to strlen(src)
+	jmp	.copy
+	.decMaxLen:
+	dec	rcx
+	jmp	.copy
+	.setMaxLen:
+	mov	rcx, rax
+	.copy:
+	mov	rdi, r8
+	rep	movsb
+	mov	byte [rdi], EOS
+	mov	rax, r8
+	ret