PHP random number C extended random number-PHP开发-php.cn

PHP random number C extended random number

高洛峰

Release： 2016-11-23 14:34:08

Original

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由于要用到固定长度的随机字符串。

首先是一段PHP代码

        $str_md5=md5(uniqid());
	$rand = mt_rand(1, 28);
	$str1=substr($str_md5,$rand,6);
	$rand = mt_rand(1, 28);
	$str2=substr($str_md5,$rand,6);
	$rand = mt_rand(1, 28);
	$str3=substr($str_md5,$rand,6);
	$code=substr($str1.$str2.$str3,0,8);

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PHP random number C extended random number

生成180000个随机字符串，图中是按照重复数量倒序排列，可以看到基本都有重复的。不过也是比较理想的。

由于想提升一下自己的C语言能力，所以用C重新写了一下随机生成字符串。

其中用到了随机数函数srand(),rand();

不过折腾一两个小时，随机数还是有问题。并发访问时时间可能几乎为同时，那么srand给的种子时间可以视为相同的。这样就导致了，产生的随机数也是一样的。从而产生的随机字符串也是一样的。循环输出随机字符串，几乎都是一模一样的。

后来想到了ukey，这个扩展可以实现唯一的ID，那么访问都产生唯一的ID，是不是可以将这个ID作为种子时间。答案是肯定的。

PHP random number C extended random number

上图是产生的随机字符串，可以自定义长度。也同样可以输出只有数字的字符串。相较PHP所产生的随机字符串重复率更低且速度更快。

PHP_FUNCTION(get_random__num_str)
{
     int length=8;
	 
     if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "l", &length) == FAILURE) 
     {
		length=8;
		
     }
	 length++;
    int flag, i;  
    char* string;  	__uint64_t timestamp = realtime();
    __uint64_t retval;
    int len;
    char buf[128];

    if (timestamp == 0ULL) {
        RETURN_FALSE;
    }

    spin_lock(lock, pid);

    if (context->last_timestamp == timestamp) {
        context->sequence = (context->sequence + 1) & context->sequence_mask;
        if (context->sequence == 0) {
            timestamp = skip_next_millis();
        }

    } else {
        context->sequence = 0; /* Back to zero */    }

    context->last_timestamp = timestamp;

    retval = ((timestamp - context->twepoch) << context->timestamp_left_shift)
           | (context->datacenter_id << context->datacenter_id_shift)
           | (worker_id << context->worker_id_shift)
           | context->sequence;

    spin_unlock(lock, pid);	//printf(&#39;%ld&#39;,retval);
	srand((unsigned)retval);
    //srand((unsigned) time(NULL ));      if ((string = (char*) emalloc(length)) == NULL )  
    {  
        //myLog("Malloc failed!flag:14\n");          RETURN_NULL() ;  
    }  
  
    for (i = 0; i < length - 1; i++)  
    {  
        flag = rand() % 3;  		
		switch (flag)  
		{  			case 0:  				string[i] = &#39;1&#39; + rand() % 5;  				break;  			case 1:  				string[i] = &#39;2&#39; + rand() % 7;  				break;  			case 2:  				string[i] = &#39;0&#39; + rand() % 10;  				break;  			default:  				string[i] = &#39;9&#39;;  				break;  
		} 
		
		
         
    }  
    string[length - 1] = &#39;\0&#39;;  
    RETURN_STRINGL(string,length,0);
}
 PHP_FUNCTION(get_random_str)
{
     int length=8;
	 
     if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "l", &length) == FAILURE) 
     {
		length=8;
		
     }
	 length++;
    int flag, i;  
    char* string;  	__uint64_t timestamp = realtime();
    __uint64_t retval;
    int len;
    char buf[128];

    if (timestamp == 0ULL) {
        RETURN_FALSE;
    }

    spin_lock(lock, pid);

    if (context->last_timestamp == timestamp) {
        context->sequence = (context->sequence + 1) & context->sequence_mask;
        if (context->sequence == 0) {
            timestamp = skip_next_millis();
        }

    } else {
        context->sequence = 0; /* Back to zero */    }

    context->last_timestamp = timestamp;

    retval = ((timestamp - context->twepoch) << context->timestamp_left_shift)
           | (context->datacenter_id << context->datacenter_id_shift)
           | (worker_id << context->worker_id_shift)
           | context->sequence;

    spin_unlock(lock, pid);	//printf(&#39;%ld&#39;,retval);
	srand((unsigned)retval);
    //srand((unsigned) time(NULL ));      if ((string = (char*) emalloc(length)) == NULL )  
    {  
        //myLog("Malloc failed!flag:14\n");          RETURN_NULL() ;  
    }  
  
    for (i = 0; i < length - 1; i++)  
    {  
        flag = rand() % 3;  		
		switch (flag)  
		{  			case 0:  				string[i] = &#39;A&#39; + rand() % 26;  				break;  			case 1:  				string[i] = &#39;a&#39; + rand() % 26;  				break;  			case 2:  				string[i] = &#39;0&#39; + rand() % 10;  				break;  			default:  				string[i] = &#39;x&#39;;  				break;  
		} 
		
		
         
    }  
    string[length - 1] = &#39;\0&#39;;  
    RETURN_STRINGL(string,length,0);
}

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PHP random number C extended random number