PHP 随机数 C扩展随机数_PHP

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);

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。

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('%ld',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] = '1' + rand() % 5; 
        break; 
      case 1: 
        string[i] = '2' + rand() % 7; 
        break; 
      case 2: 
        string[i] = '0' + rand() % 10; 
        break; 
      default: 
        string[i] = '9'; 
        break; 
    } 
     
     
     
  } 
  string[length - 1] = '\0'; 
  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('%ld',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] = 'A' + rand() % 26; 
        break; 
      case 1: 
        string[i] = 'a' + rand() % 26; 
        break; 
      case 2: 
        string[i] = '0' + rand() % 10; 
        break; 
      default: 
        string[i] = 'x'; 
        break; 
    } 
     
     
     
  } 
  string[length - 1] = '\0'; 
  RETURN_STRINGL(string,length,0);
}