min[u](),max[u](),islower(),isupper(),print(),puts(),strlen(),strcpy(),strcat()

string.asm

@@ -0,0 +1,67 @@
+section	.text
+	global	strlen
+	global	strcpy
+	global	strcat
+
+;----- strlen(char* str) -----;
+; return value: amount of characters before EOS was found
+strlen:
+	push	rbp
+	mov	rbp, rsp
+
+	xor	rax, rax
+	.findEOS:
+		cmp	byte [rdi+rax], 0x0
+		je	.quit
+		inc	rax
+		jmp	.findEOS
+
+	.quit:
+	leave
+	ret
+;----- strcpy(char* dest, char* src) -----;
+; return value: pointer to dest or NULL if nothing was copied
+strcpy:
+	push	rbp
+	mov	rbp, rsp
+
+	push	rdi
+	sub	rsp, 8
+	xor	rax, rax
+	xor	rcx, rcx
+	.loop:
+		cmp	byte [rsi], 0x0
+		je	.0f
+		mov	r10b, byte [rsi]
+		mov	byte [rdi], r10b
+		inc	rsi
+		inc	rdi
+		inc	rcx
+		jmp	.loop
+
+	.0f:
+	pop	rax
+	add	rsp, 8
+	cmp	rcx, 0
+	jne	.quit
+	xor	rax, rax
+
+	.quit:
+	leave
+	ret
+;----- strcat(char* dest, char* src) -----;
+; return value: pointer to dest
+strcat:
+	push	rbp
+	mov	rbp, rsp
+
+	push	rdi
+	sub	rsp, 8
+	call	strlen
+	add	rdi, rax
+	call	strcpy
+	add	rsp, 8
+	pop	rdi
+
+	leave
+	ret