1/* Copyright (C) 1996-2021 Free Software Foundation, Inc.
2   This file is part of the GNU C Library.
3
4   The GNU C Library is free software; you can redistribute it and/or
5   modify it under the terms of the GNU Lesser General Public
6   License as published by the Free Software Foundation; either
7   version 2.1 of the License, or (at your option) any later version.
8
9   The GNU C Library is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12   Lesser General Public License for more details.
13
14   You should have received a copy of the GNU Lesser General Public
15   License along with the GNU C Library.  If not, see
16   <https://www.gnu.org/licenses/>.  */
17
18/* Append no more than COUNT characters from the null-terminated string SRC
19   to the null-terminated string DST.  Always null-terminate the new DST.  */
20
21#include <sysdep.h>
22
23	.text
24
25ENTRY(strncat)
26	ldgp	gp, 0(pv)
27#ifdef PROF
28	.set noat
29	lda	AT, _mcount
30	jsr	AT, (AT), _mcount
31	.set at
32#endif
33	.prologue 1
34
35	mov	a0, v0		# set up return value
36	beq	a2, $zerocount
37
38	/* Find the end of the string.  */
39
40	ldq_u   t0, 0(a0)	# load first quadword (a0 may be misaligned)
41	lda     t1, -1(zero)
42	insqh   t1, a0, t1
43	andnot  a0, 7, a0
44	or      t1, t0, t0
45	cmpbge  zero, t0, t1	# t1 <- bitmask: bit i == 1 <==> i-th byte == 0
46	bne     t1, $found
47
48$loop:	ldq     t0, 8(a0)
49	addq    a0, 8, a0	# addr += 8
50	cmpbge  zero, t0, t1
51	beq     t1, $loop
52
53$found:	negq    t1, t2		# clear all but least set bit
54	and     t1, t2, t1
55
56	and     t1, 0xf0, t2	# binary search for that set bit
57	and	t1, 0xcc, t3
58	and	t1, 0xaa, t4
59	cmovne	t2, 4, t2
60	cmovne	t3, 2, t3
61	cmovne	t4, 1, t4
62	addq	t2, t3, t2
63	addq	a0, t4, a0
64	addq	a0, t2, a0
65
66	/* Now do the append.  */
67
68	jsr	t9, __stxncpy
69
70	/* Worry about the null termination.  */
71
72	zapnot	t0, t8, t1	# was last byte a null?
73	bne	t1, 0f
74	ret
75
760:	and	t10, 0x80, t1
77	bne	t1, 1f
78
79	/* Here there are bytes left in the current word.  Clear one.  */
80	addq	t10, t10, t10	# end-of-count bit <<= 1
81	zap	t0, t10, t0
82	stq_u	t0, 0(a0)
83	ret
84
851:	/* Here we must read the next DST word and clear the first byte.  */
86	ldq_u	t0, 8(a0)
87	zap	t0, 1, t0
88	stq_u	t0, 8(a0)
89
90$zerocount:
91	ret
92
93	END(strncat)
94