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/* 
 *      HEADER:         ; 
 *      TITLE:          stristr() - substring search function; 
 *      DATE:           10/27/1989; 
 *      DESCRIPTION:    "strstr() that ignores case distinctions"; 
 *      VERSION:        1.0; 
 *      FILENAME:       STRISTR.C; 
 *      SEE-ALSO:       PB.DOC; 
 *      AUTHORS:        Michael Kelly; 
 */ 
 
 
 
#include "stristr.h" 
 
 
 
/* 
 *  strstr() that ignores case distinctions 
 */ 
char *stristr(const char *string, const char *substr) 
{ 
    char *str1, *str2, *sentinel; 
    size_t string_len, substr_len, n; 
    int dif; 
 
 
    if(! *substr) 
	return (char *) string; 
 
    string_len = strlen(string); 
    substr_len = strlen(substr); 
 
    if(substr_len > string_len) 
	return NULL; 
 
    sentinel = (char *) &string[string_len - substr_len]; 
 
    do  { 
	str1 = (char *) string; 
	str2 = (char *) substr; 
	n = substr_len; 
 
	while(n--) 
	    if(dif = tolower(*str1++) - tolower(*str2++)) 
		break; 
 
	if(! dif) 
	    return (char *) string; 
 
	} while(++string <= sentinel); 
 
	return NULL; 
 
}