1/* Copyright (C) 1996-2024 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/* Copy no more than COUNT bytes of the null-terminated string from
19 SRC to DST. If SRC does not cover all of COUNT, the balance is
20 zeroed. */
21
22#include <sysdep.h>
23
24 .set noat
25 .set noreorder
26
27 .text
28
29ENTRY(strncpy)
30 ldgp gp, 0(pv)
31#ifdef PROF
32 lda AT, _mcount
33 jsr AT, (AT), _mcount
34#endif
35 .prologue 1
36
37 mov a0, v0 # set return value now
38 beq a2, $zerocount
39 jsr t9, __stxncpy # do the work of the copy
40
41 bne a2, $multiword # do we have full words left?
42
43 .align 3
44 subq t8, 1, t2 # e0 : guess not
45 subq t10, 1, t3 # .. e1 :
46 or t2, t8, t2 # e0 : clear the bits between the last
47 or t3, t10, t3 # .. e1 : written byte and the last byte in
48 andnot t3, t2, t3 # e0 : COUNT
49 zap t0, t3, t0 # e1 :
50 stq_u t0, 0(a0) # e0 :
51 ret # .. e1 :
52
53$multiword:
54 subq t8, 1, t7 # e0 : clear the final bits in the prev
55 or t7, t8, t7 # e1 : word
56 zapnot t0, t7, t0 # e0 :
57 subq a2, 1, a2 # .. e1 :
58 stq_u t0, 0(a0) # e0 :
59 addq a0, 8, a0 # .. e1 :
60
61 beq a2, 1f # e1 :
62 blbc a2, 0f # e1 :
63
64 stq_u zero, 0(a0) # e0 : zero one word
65 subq a2, 1, a2 # .. e1 :
66 addq a0, 8, a0 # e0 :
67 beq a2, 1f # .. e1 :
68
690: stq_u zero, 0(a0) # e0 : zero two words
70 subq a2, 2, a2 # .. e1 :
71 stq_u zero, 8(a0) # e0 :
72 addq a0, 16, a0 # .. e1 :
73 bne a2, 0b # e1 :
74 unop
75
761: ldq_u t0, 0(a0) # e0 : clear the leading bits in the final
77 subq t10, 1, t7 # .. e1 : word
78 or t7, t10, t7 # e0 :
79 zap t0, t7, t0 # e1 (stall)
80 stq_u t0, 0(a0) # e0 :
81
82$zerocount:
83 ret # .. e1 :
84
85 END(strncpy)
86libc_hidden_builtin_def (strncpy)
87

source code of glibc/sysdeps/alpha/strncpy.S