strstr.c

Vovida 社区开源的 SIP 协议源码

/*
 * Program:	Substring search
 *
 * Author:	Mark Crispin
 *		Networks and Distributed Computing
 *		Computing & Communications
 *		University of Washington
 *		Administration Building, AG-44
 *		Seattle, WA  98195
 *
 * Date:	11 May 1989
 * Last Edited:	12 November 1993
 *
 * Copyright 1993 by the University of Washington
 *
 *  Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose and without fee is hereby granted, provided
 * that the above copyright notice appears in all copies and that both the
 * above copyright notice and this permission notice appear in supporting
 * documentation, and that the name of the University of Washington not be
 * used in advertising or publicity pertaining to distribution of the software
 * without specific, written prior permission.  This software is made
 * available "as is", and
 * THE UNIVERSITY OF WASHINGTON DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
 * WITH REGARD TO THIS SOFTWARE, INCLUDING WITHOUT LIMITATION ALL IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, AND IN
 * NO EVENT SHALL THE UNIVERSITY OF WASHINGTON BE LIABLE FOR ANY SPECIAL,
 * INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, TORT
 * (INCLUDING NEGLIGENCE) OR STRICT LIABILITY, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */

/* Return pointer to first occurance in string of a substring
 * Accepts: source pointer
 *	    substring pointer
 * Returns: pointer to substring in source or NIL if not found
 */

char *strstr (char *cs,char *ct)
{
  char *s;
  char *t;
  while (cs = strchr (cs,*ct)) {/* for each occurance of the first character */
				/* see if remainder of string matches */
    for (s = cs + 1, t = ct + 1; *t && *s == *t; s++, t++);
    if (!*t) return cs;		/* if ran out of substring then have match */
    cs++;			/* try from next character */
  }
  return NIL;			/* not found */
}