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annotate lib/strcasestr.c @ 40186:8964917f9574

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author Karl Berry <karl@freefriends.org>
date Mon, 18 Feb 2019 08:02:49 -0800
parents b06060465f09
children
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1 /* Case-insensitive searching in a string.
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2 Copyright (C) 2005-2019 Free Software Foundation, Inc.
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3 Written by Bruno Haible <bruno@clisp.org>, 2005.
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4
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5 This program is free software; you can redistribute it and/or modify
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6 it under the terms of the GNU General Public License as published by
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7 the Free Software Foundation; either version 2, or (at your option)
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8 any later version.
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9
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10 This program is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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13 GNU General Public License for more details.
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14
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15 You should have received a copy of the GNU General Public License
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16 along with this program; if not, see <https://www.gnu.org/licenses/>. */
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17
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18 #include <config.h>
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19
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20 /* Specification. */
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21 #include <string.h>
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22
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23 #include <ctype.h>
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24 #include <stdbool.h>
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25 #include <strings.h>
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26
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27 #define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))
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28
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29 /* Two-Way algorithm. */
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30 #define RETURN_TYPE char *
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31 #define AVAILABLE(h, h_l, j, n_l) \
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32 (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
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33 && ((h_l) = (j) + (n_l)))
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34 #define CANON_ELEMENT(c) TOLOWER (c)
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35 #define CMP_FUNC(p1, p2, l) \
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36 strncasecmp ((const char *) (p1), (const char *) (p2), l)
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37 #include "str-two-way.h"
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38
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39 /* Find the first occurrence of NEEDLE in HAYSTACK, using
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40 case-insensitive comparison. This function gives unspecified
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41 results in multibyte locales. */
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42 char *
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43 strcasestr (const char *haystack_start, const char *needle_start)
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44 {
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45 const char *haystack = haystack_start;
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46 const char *needle = needle_start;
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47 size_t needle_len; /* Length of NEEDLE. */
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48 size_t haystack_len; /* Known minimum length of HAYSTACK. */
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49 bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */
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50
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51 /* Determine length of NEEDLE, and in the process, make sure
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52 HAYSTACK is at least as long (no point processing all of a long
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53 NEEDLE if HAYSTACK is too short). */
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54 while (*haystack && *needle)
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55 {
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56 ok &= (TOLOWER ((unsigned char) *haystack)
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57 == TOLOWER ((unsigned char) *needle));
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58 haystack++;
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59 needle++;
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60 }
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61 if (*needle)
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62 return NULL;
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63 if (ok)
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64 return (char *) haystack_start;
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65 needle_len = needle - needle_start;
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66 haystack = haystack_start + 1;
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67 haystack_len = needle_len - 1;
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68
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69 /* Perform the search. Abstract memory is considered to be an array
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70 of 'unsigned char' values, not an array of 'char' values. See
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71 ISO C 99 section 6.2.6.1. */
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72 if (needle_len < LONG_NEEDLE_THRESHOLD)
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73 return two_way_short_needle ((const unsigned char *) haystack,
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74 haystack_len,
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75 (const unsigned char *) needle_start,
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76 needle_len);
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77 return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
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78 (const unsigned char *) needle_start,
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79 needle_len);
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80 }
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81
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82 #undef LONG_NEEDLE_THRESHOLD