char*, wchar_t* 替换子串

char* replace_a(char*s1,char*s2,char*s3=NULL)
{
    char *p,*from,*to,*begin=s1;
    int c1,c2,c3,c;         //串长度及计数
    c2=strlen(s2);
    c3=(s3!=NULL)?strlen(s3):0;
    if(c2==0)return s1;     //注意要退出
    while(true)             //替换所有出现的串
    {
        c1=strlen(begin);
        p=strstr(begin,s2); //出现位置
        if(p==NULL)         //没找到
            return s1;
        if(c2>c3)           //串往前移
        {
            from=p+c2;
            to=p+c3;
            c=c1-c2+begin-p+1;
            while(c--)
                *to++=*from++;
        }
        else if(c2<c3)      //串往后移
        {
            from=begin+c1;
            to=from-c2+c3;
            c=from-p-c2+1;
            while(c--)
                *to--=*from--;
        }
        if(c3)              //完成替换
        {
            from=s3,to=p,c=c3;
            while(c--)
                *to++=*from++;
        }
        begin=p+c3;         //新的查找位置
    }
}

wchar_t* replace_w(wchar_t* s1, wchar_t* s2, wchar_t* s3 = NULL)
{
	wchar_t* p, * from, * to, * begin = s1;
	int c1, c2, c3, c;         //串长度及计数
	c2 = wcslen(s2);
	c3 = (s3 != NULL) ? wcslen(s3) : 0;
	if (c2 == 0)return s1;     //注意要退出
	while (true)             //替换所有出现的串
	{
		c1 = wcslen(begin);
		p = wcsstr(begin, s2); //出现位置
		if (p == NULL)         //没找到
			return s1;
		if (c2 > c3)           //串往前移
		{
			from = p + c2;
			to = p + c3;
			c = c1 - c2 + begin - p + 1;
			while (c--)
				* to++ = *from++;
		}
		else if (c2 < c3)      //串往后移
		{
			from = begin + c1;
			to = from - c2 + c3;
			c = from - p - c2 + 1;
			while (c--)
				* to-- = *from--;
		}
		if (c3)              //完成替换
		{
			from = s3, to = p, c = c3;
			while (c--)
				* to++ = *from++;
		}
		begin = p + c3;         //新的查找位置
	}
}