1/*
2Copyright (c) 2009 Nick Clifton <nickc@redhat.com>
3 */
4#include <picolibc.h>
5
6	.file	"strncat.S"
7
8	.section .text
9	.global  _strncat
10	.type	 _strncat,@function
11_strncat:
12	;; On entry: r1 => Destination
13	;;           r2 => Source
14	;; 	     r3 => Max number of bytes to copy
15#ifdef __RX_DISALLOW_STRING_INSNS__
16	cmp	#0, r3		; If max is zero we have nothing to do.
17	beq	2f
18
19	mov 	r1, r4		; Leave the desintation pointer intact for the return value.
20
211:	mov.b	[r4+], r5	; Find the NUL byte at the end of the destination.
22	cmp	#0, r5
23	bne	1b
24
25	sub	#1, r4
26
273:	mov.b	[r2+], r5	; Copy bytes from the source into the destination ...
28	mov.b	r5, [r4+]
29	cmp	#0, r5		; ... until we reach a NUL byte ...
30	beq 	2f
31	sub	#1, r3
32	bne	3b		; ... or we have copied N bytes.
33
342:	rts
35#else
36	mov 	r1, r4		; Save a copy of the dest pointer.
37	mov 	r2, r5		; Save a copy of the source pointer.
38	mov 	r3, r14		; Save a copy of the byte count.
39
40	mov	#0,  r2		; Search for the NUL byte.
41	mov 	#-1, r3		; Search until we run out of memory.
42	suntil.b		; Find the end of the destination string.
43	sub	#1, r1		; suntil.b leaves r1 pointing to the byte beyond the NUL.
44
45	mov	r14, r3		; Restore the limit on the number of bytes copied.
46	mov	r5, r2		; Restore the source pointer.
47	mov	r1, r5		; Save a copy of the dest pointer.
48	smovu			; Copy source to destination.
49
50	add	#0, r14, r3	; Restore the number of bytes to copy (again), but this time set the Z flag as well.
51	beq	1f  		; If we copied 0 bytes then we already know that the dest string is NUL terminated, so we do not have to do anything.
52	mov	#0, r2		; Otherwise we must check to see if a NUL byte
53	mov	r5, r1		;  was included in the bytes that were copied.
54	suntil.b
55	beq	1f		; Z flag is set if a match was found.
56	add	r14, r5		; Point at byte after end of copied bytes.
57	mov.b	#0, [r5]	; Store a NUL there.
581:
59	mov	r4, r1		; Return the original dest pointer.
60	rts
61#endif
62	.size _strncat, . - _strncat
63
64