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434
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1 /* strncasecmp.c -- case insensitive string comparator
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2 Copyright (C) 1998-1999, 2005-2007, 2009-2010 Free Software Foundation, Inc.
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3
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4 This program is free software; you can redistribute it and/or modify
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5 it under the terms of the GNU General Public License as published by
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6 the Free Software Foundation; either version 3, or (at your option)
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7 any later version.
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8
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9 This program is distributed in the hope that it will be useful,
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10 but WITHOUT ANY WARRANTY; without even the implied warranty of
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11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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12 GNU General Public License for more details.
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13
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14 You should have received a copy of the GNU General Public License
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15 along with this program; if not, write to the Free Software Foundation,
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16 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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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 <limits.h>
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25
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26 #define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))
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27
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28 /* Compare no more than N bytes of strings S1 and S2, ignoring case,
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29 returning less than, equal to or greater than zero if S1 is
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30 lexicographically less than, equal to or greater than S2.
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31 Note: This function cannot work correctly in multibyte locales. */
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32
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33 int
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34 strncasecmp (const char *s1, const char *s2, size_t n)
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35 {
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36 register const unsigned char *p1 = (const unsigned char *) s1;
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37 register const unsigned char *p2 = (const unsigned char *) s2;
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38 unsigned char c1, c2;
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39
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40 if (p1 == p2 || n == 0)
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41 return 0;
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42
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43 do
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44 {
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45 c1 = TOLOWER (*p1);
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46 c2 = TOLOWER (*p2);
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47
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48 if (--n == 0 || c1 == '\0')
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49 break;
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50
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51 ++p1;
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52 ++p2;
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53 }
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54 while (c1 == c2);
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55
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56 if (UCHAR_MAX <= INT_MAX)
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57 return c1 - c2;
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58 else
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59 /* On machines where 'char' and 'int' are types of the same size, the
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60 difference of two 'unsigned char' values - including the sign bit -
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61 doesn't fit in an 'int'. */
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62 return (c1 > c2 ? 1 : c1 < c2 ? -1 : 0);
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63 }
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