1 /* strncasecmp.c -- case insensitive string comparator 2 Copyright (C) 1998-1999, 2005-2007, 2009-2021 Free Software Foundation, Inc. 3 4 This file is free software: you can redistribute it and/or modify 5 it under the terms of the GNU Lesser General Public License as 6 published by the Free Software Foundation; either version 2.1 of the 7 License, or (at your option) any later version. 8 9 This file 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 12 GNU Lesser General Public License for more details. 13 14 You should have received a copy of the GNU Lesser General Public License 15 along with this program. If not, see <https://www.gnu.org/licenses/>. */ 16 17 #include <config.h> 18 19 /* Specification. */ 20 #include <string.h> 21 22 #include <ctype.h> 23 #include <limits.h> 24 25 #define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch)) 26 27 /* Compare no more than N bytes of strings S1 and S2, ignoring case, 28 returning less than, equal to or greater than zero if S1 is 29 lexicographically less than, equal to or greater than S2. 30 Note: This function cannot work correctly in multibyte locales. */ 31 32 int 33 strncasecmp (const char *s1, const char *s2, size_t n) /* */ 34 { 35 register const unsigned char *p1 = (const unsigned char *) s1; 36 register const unsigned char *p2 = (const unsigned char *) s2; 37 unsigned char c1, c2; 38 39 if (p1 == p2 || n == 0) 40 return 0; 41 42 do 43 { 44 c1 = TOLOWER (*p1); 45 c2 = TOLOWER (*p2); 46 47 if (--n == 0 || c1 == '\0') 48 break; 49 50 ++p1; 51 ++p2; 52 } 53 while (c1 == c2); 54 55 if (UCHAR_MAX <= INT_MAX) 56 return c1 - c2; 57 else 58 /* On machines where 'char' and 'int' are types of the same size, the 59 difference of two 'unsigned char' values - including the sign bit - 60 doesn't fit in an 'int'. */ 61 return _GL_CMP (c1, c2); 62 }