1 | /* Copyright (C) 1992-2024 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 | #define NO_MEMPCPY_STPCPY_REDIRECT |
19 | #include <string.h> |
20 | #include <stdint.h> |
21 | #include <memcopy.h> |
22 | #include <string-fzb.h> |
23 | #include <string-misc.h> |
24 | |
25 | #undef __stpcpy |
26 | #undef stpcpy |
27 | |
28 | #ifndef STPCPY |
29 | # define STPCPY __stpcpy |
30 | #endif |
31 | |
32 | static __always_inline char * |
33 | write_byte_from_word (op_t *dest, op_t word) |
34 | { |
35 | char *d = (char *) dest; |
36 | for (size_t i = 0; i < OPSIZ; i++, ++d) |
37 | { |
38 | char c = extractbyte (x: word, idx: i); |
39 | *d = c; |
40 | if (c == '\0') |
41 | break; |
42 | } |
43 | return d; |
44 | } |
45 | |
46 | static __always_inline char * |
47 | stpcpy_aligned_loop (op_t *restrict dst, const op_t *restrict src) |
48 | { |
49 | op_t word; |
50 | while (1) |
51 | { |
52 | word = *src++; |
53 | if (has_zero (x: word)) |
54 | break; |
55 | *dst++ = word; |
56 | } |
57 | |
58 | return write_byte_from_word (dest: dst, word); |
59 | } |
60 | |
61 | static __always_inline char * |
62 | stpcpy_unaligned_loop (op_t *restrict dst, const op_t *restrict src, |
63 | uintptr_t ofs) |
64 | { |
65 | op_t w2a = *src++; |
66 | uintptr_t sh_1 = ofs * CHAR_BIT; |
67 | uintptr_t sh_2 = OPSIZ * CHAR_BIT - sh_1; |
68 | |
69 | op_t w2 = MERGE (w2a, sh_1, (op_t)-1, sh_2); |
70 | if (!has_zero (x: w2)) |
71 | { |
72 | op_t w2b; |
73 | |
74 | /* Unaligned loop. The invariant is that W2B, which is "ahead" of W1, |
75 | does not contain end-of-string. Therefore it is safe (and necessary) |
76 | to read another word from each while we do not have a difference. */ |
77 | while (1) |
78 | { |
79 | w2b = *src++; |
80 | w2 = MERGE (w2a, sh_1, w2b, sh_2); |
81 | /* Check if there is zero on w2a. */ |
82 | if (has_zero (x: w2)) |
83 | goto out; |
84 | *dst++ = w2; |
85 | if (has_zero (x: w2b)) |
86 | break; |
87 | w2a = w2b; |
88 | } |
89 | |
90 | /* Align the final partial of P2. */ |
91 | w2 = MERGE (w2b, sh_1, 0, sh_2); |
92 | } |
93 | |
94 | out: |
95 | return write_byte_from_word (dest: dst, word: w2); |
96 | } |
97 | |
98 | |
99 | /* Copy SRC to DEST, returning the address of the terminating '\0' in DEST. */ |
100 | char * |
101 | STPCPY (char *dest, const char *src) |
102 | { |
103 | /* Copy just a few bytes to make DEST aligned. */ |
104 | size_t len = (-(uintptr_t) dest) % OPSIZ; |
105 | for (; len != 0; len--, ++dest) |
106 | { |
107 | char c = *src++; |
108 | *dest = c; |
109 | if (c == '\0') |
110 | return dest; |
111 | } |
112 | |
113 | /* DEST is now aligned to op_t, SRC may or may not be. */ |
114 | uintptr_t ofs = (uintptr_t) src % OPSIZ; |
115 | return ofs == 0 ? stpcpy_aligned_loop (dst: (op_t*) dest, src: (const op_t *) src) |
116 | : stpcpy_unaligned_loop (dst: (op_t*) dest, |
117 | src: (const op_t *) (src - ofs) , ofs); |
118 | } |
119 | weak_alias (__stpcpy, stpcpy) |
120 | libc_hidden_def (__stpcpy) |
121 | libc_hidden_builtin_def (stpcpy) |
122 | |