Adds strcat()

src/string.asm

@@ -3,6 +3,7 @@
 section .text
 	global	strlen
 	global	strcpy
+	global	strcat
 
 ;----- strlen(*str[]) -----;
 ; Gets the length of given string
@@ -24,7 +25,7 @@ strlen:
 ;----- 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
+; Return value: Pointer to dest[]
 ; Used registers:
 ;	rax*	(ret) Pointer to dest[]
 ;	rdi*	(arg) Pointer to dest[]
@@ -43,9 +44,48 @@ strcpy:
 	cmp	rcx, rdx
 	jb	.copy
 	dec	rcx
-	.copy
+	.copy:
 	mov	rdi, r8
 	rep	movsb
 	mov	byte [rdi], EOS
 	mov	rax, r8
 	ret
+
+;----- strcat(*dest[], *src[], maxLength) -----;
+; Concatenate src[] into 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) Size of dest[]
+;	rcx*	Counter for movsb
+;	r8*	Backup for rdi
+;	r9*	Backup for rsi
+;	r10*	Current length of dest[]
+strcat:
+	mov	r8, rdi
+	mov	r9, rsi
+	mov	rdi, rsi
+	call	strlen ;16
+	mov	rcx, rax
+	mov	rdi, r8
+	call	strlen ;20
+	mov	r10, rax
+	mov	rdi, r8
+	add	rcx, rax ;36
+	cmp	rcx, rdx ;36 <> 32
+	cmova	rcx, rdx
+	cmp	rcx, rdx
+	jb	.copy
+	dec	rcx
+	.copy:	
+	mov	rdi, r8
+	mov	rsi, r9
+	add	rdi, r10
+	sub	rcx, r10
+	cld
+	rep	movsb
+	mov	byte [rdi], EOS
+	mov	rax, r8
+	ret

src/tests.asm

@@ -8,6 +8,7 @@ extern	puts
 ; string.asm
 extern	strlen
 extern	strcpy
+extern	strcat
 ; convert.asm
 
 section .rodata
@@ -15,6 +16,7 @@ section .rodata
 	TEST_puts		equ	1
 	TEST_strlen		equ	1
 	TEST_strcpy		equ	1
+	TEST_strcat		equ	1
 
 	str1			db	"Hello, world!",EOS
 	str2			db	"Hello, World!",EOS
@@ -39,11 +41,16 @@ section .rodata
 	strcpy3			db	TAB,"strcpy(strBuff1, str1, 32): ",NL,TAB,TAB,EOS
 	strcpy4			db	TAB,"strcpy(strBuff1, str5, 32): ",NL,TAB,TAB,EOS
 
+	; strcat()
+	msgStrcat		db	"TEST strcat()",NL,EOS
+	strcat1			db	TAB,"strcat(strBuff2, str1, 32): ",NL,TAB,TAB,EOS
+	strcat2			db	TAB,"strcat(strBuff2, str5, 32): ",NL,TAB,TAB,EOS
+
 section .data
 
 section .bss
 	strBuff1		resb	32
-	strBuff2		resb	4
+	strBuff2		resb	32
 
 section .text
 	global _start
@@ -125,6 +132,34 @@ _start:
 	call	puts
 %endif
 
+;---
+;--- strcat
+;---
+%if TEST_strcat
+	lea	rdi, [rel msgStrcat]
+	call	print
+
+	; TEST 1
+	lea	rdi, [rel strcat1]
+	call	print
+	lea	rdi, [rel strBuff2]
+	lea	rsi, [rel str1]
+	mov	rcx, 32
+	call	strcat
+	mov	rdi, rax
+	call	puts
+
+	; TEST 3
+	lea	rdi, [rel strcat2]
+	call	print
+	lea	rdi, [rel strBuff2]
+	lea	rsi, [rel str5]
+	mov	rcx, 32
+	call	strcat
+	mov	rdi, rax
+	call	puts
+%endif
+
 ;---
 ;--- exit()
 ;---