| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame^] | 1 | /* Return the offset of one string within another. |
| 2 | Copyright (C) 1994-2015 Free Software Foundation, Inc. |
| 3 | This file is part of the GNU C Library. |
| 4 | |
| 5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public |
| 7 | License as published by the Free Software Foundation; either |
| 8 | version 2.1 of the License, or (at your option) any later version. |
| 9 | |
| 10 | The GNU C Library is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | Lesser General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Lesser General Public |
| 16 | License along with the GNU C Library; if not, see |
| 17 | <http://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | /* This particular implementation was written by Eric Blake, 2008. */ |
| 20 | |
| 21 | #ifndef _LIBC |
| 22 | # include <config.h> |
| 23 | #endif |
| 24 | |
| 25 | /* Specification of strstr. */ |
| 26 | #include <string.h> |
| 27 | |
| 28 | #include <stdbool.h> |
| 29 | |
| 30 | #ifndef _LIBC |
| 31 | # define __builtin_expect(expr, val) (expr) |
| 32 | #endif |
| 33 | |
| 34 | #define RETURN_TYPE char * |
| 35 | #define AVAILABLE(h, h_l, j, n_l) \ |
| 36 | (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \ |
| 37 | && ((h_l) = (j) + (n_l))) |
| 38 | #define CHECK_EOL (1) |
| 39 | #define RET0_IF_0(a) if (!a) goto ret0 |
| 40 | #include "str-two-way.h" |
| 41 | |
| 42 | #undef strstr |
| 43 | |
| 44 | #ifndef STRSTR |
| 45 | #define STRSTR strstr |
| 46 | #endif |
| 47 | |
| 48 | /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK |
| 49 | if NEEDLE is empty, otherwise NULL if NEEDLE is not found in |
| 50 | HAYSTACK. */ |
| 51 | char * |
| 52 | STRSTR (const char *haystack_start, const char *needle_start) |
| 53 | { |
| 54 | const char *haystack = haystack_start; |
| 55 | const char *needle = needle_start; |
| 56 | size_t needle_len; /* Length of NEEDLE. */ |
| 57 | size_t haystack_len; /* Known minimum length of HAYSTACK. */ |
| 58 | bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */ |
| 59 | |
| 60 | /* Determine length of NEEDLE, and in the process, make sure |
| 61 | HAYSTACK is at least as long (no point processing all of a long |
| 62 | NEEDLE if HAYSTACK is too short). */ |
| 63 | while (*haystack && *needle) |
| 64 | ok &= *haystack++ == *needle++; |
| 65 | if (*needle) |
| 66 | return NULL; |
| 67 | if (ok) |
| 68 | return (char *) haystack_start; |
| 69 | |
| 70 | /* Reduce the size of haystack using strchr, since it has a smaller |
| 71 | linear coefficient than the Two-Way algorithm. */ |
| 72 | needle_len = needle - needle_start; |
| 73 | haystack = strchr (haystack_start + 1, *needle_start); |
| 74 | if (!haystack || __builtin_expect (needle_len == 1, 0)) |
| 75 | return (char *) haystack; |
| 76 | needle -= needle_len; |
| 77 | haystack_len = (haystack > haystack_start + needle_len ? 1 |
| 78 | : needle_len + haystack_start - haystack); |
| 79 | |
| 80 | /* Perform the search. Abstract memory is considered to be an array |
| 81 | of 'unsigned char' values, not an array of 'char' values. See |
| 82 | ISO C 99 section 6.2.6.1. */ |
| 83 | if (needle_len < LONG_NEEDLE_THRESHOLD) |
| 84 | return two_way_short_needle ((const unsigned char *) haystack, |
| 85 | haystack_len, |
| 86 | (const unsigned char *) needle, needle_len); |
| 87 | return two_way_long_needle ((const unsigned char *) haystack, haystack_len, |
| 88 | (const unsigned char *) needle, needle_len); |
| 89 | } |
| 90 | libc_hidden_builtin_def (strstr) |
| 91 | |
| 92 | #undef LONG_NEEDLE_THRESHOLD |