/* * strstr.c -- * * Source code for the "strstr" library routine. * * Copyright (c) 1988-1993 The Regents of the University of California. * Copyright (c) 1994 Sun Microsystems, Inc. * * See the file "license.terms" for information on usage and redistribution * of this file, and for a DISCLAIMER OF ALL WARRANTIES. * * RCS: @(#) $Id: strstr.c,v 1.1.1.1 2007/07/10 15:04:23 duncan Exp $ */ #include #ifndef NULL #define NULL 0 #endif /* *---------------------------------------------------------------------- * * strstr -- * * Locate the first instance of a substring in a string. * * Results: * If string contains substring, the return value is the * location of the first matching instance of substring * in string. If string doesn't contain substring, the * return value is 0. Matching is done on an exact * character-for-character basis with no wildcards or special * characters. * * Side effects: * None. * *---------------------------------------------------------------------- */ char * strstr(string, substring) register char *string; /* String to search. */ char *substring; /* Substring to try to find in string. */ { register char *a, *b; /* First scan quickly through the two strings looking for a * single-character match. When it's found, then compare the * rest of the substring. */ b = substring; if (*b == 0) { return string; } for ( ; *string != 0; string += 1) { if (*string != *b) { continue; } a = string; while (1) { if (*b == 0) { return string; } if (*a++ != *b++) { break; } } b = substring; } return NULL; }