1/* 2 * strstr.c -- 3 * 4 * Source code for the "strstr" library routine. 5 * 6 * Copyright (c) 1988-1993 The Regents of the University of California. 7 * Copyright (c) 1994 Sun Microsystems, Inc. 8 * 9 * See the file "license.terms" for information on usage and redistribution 10 * of this file, and for a DISCLAIMER OF ALL WARRANTIES. 11 * 12 * RCS: @(#) $Id: strstr.c,v 1.3.2.1 2005/04/12 18:28:56 kennykb Exp $ 13 */ 14 15#include <tcl.h> 16#ifndef NULL 17#define NULL 0 18#endif 19 20/* 21 *---------------------------------------------------------------------- 22 * 23 * strstr -- 24 * 25 * Locate the first instance of a substring in a string. 26 * 27 * Results: 28 * If string contains substring, the return value is the 29 * location of the first matching instance of substring 30 * in string. If string doesn't contain substring, the 31 * return value is 0. Matching is done on an exact 32 * character-for-character basis with no wildcards or special 33 * characters. 34 * 35 * Side effects: 36 * None. 37 * 38 *---------------------------------------------------------------------- 39 */ 40 41char * 42strstr(string, substring) 43 register char *string; /* String to search. */ 44 char *substring; /* Substring to try to find in string. */ 45{ 46 register char *a, *b; 47 48 /* First scan quickly through the two strings looking for a 49 * single-character match. When it's found, then compare the 50 * rest of the substring. 51 */ 52 53 b = substring; 54 if (*b == 0) { 55 return string; 56 } 57 for ( ; *string != 0; string += 1) { 58 if (*string != *b) { 59 continue; 60 } 61 a = string; 62 while (1) { 63 if (*b == 0) { 64 return string; 65 } 66 if (*a++ != *b++) { 67 break; 68 } 69 } 70 b = substring; 71 } 72 return NULL; 73} 74