runestrstr.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/*
 * The authors of this software are Rob Pike and Ken Thompson.
 *              Copyright (c) 2002 by Lucent Technologies.
 * Permission to use, copy, modify, and distribute this software for any
 * purpose without fee is hereby granted, provided that this entire notice
 * is included in all copies of any software which is or includes a copy
 * or modification of this software and in all copies of the supporting
 * documentation for such software.
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
 */
#include <stdarg.h>
#include <string.h>
#include "utf.h"
#include "utfdef.h"

/*
 * Return pointer to first occurrence of s2 in s1,
 * 0 if none
 */
Rune*
runestrstr(Rune *s1, Rune *s2)
{
	Rune *p, *pa, *pb;
	int c0, c;

	c0 = *s2;
	if(c0 == 0)
		return s1;
	s2++;
	for(p=runestrchr(s1, c0); p; p=runestrchr(p+1, c0)) {
		pa = p;
		for(pb=s2;; pb++) {
			c = *pb;
			if(c == 0)
				return p;
			if(c != *++pa)
				break;
		}
	}
	return 0;
}