根据Javascript中的字符串输入生成唯一编号 [英] Generate unique number based on string input in Javascript

问题描述

在过去，我创建了一个从字符串生成唯一ID（数字）的函数。今天我发现它不是那么独特。从来没有看到过问题。今天两个不同的输入生成相同的id（数字）。

In the past I have made a function that generates an unique id (number) from a string. Today I discover that it is not as unique as should be. Never saw a problem before with it. Today two different inputs generates the same id (number).

我在Delphi，C ++，PHP和Javascript中使用相同的技术来生成相同的id，所以没有区别当项目涉及不同的语言时。例如，对于HTML id，tempfiles等，这可以很方便地进行通信。

I use the same technique in Delp C++, PHP and Javascript to generate the same id's so there is no difference when different languages are involved to a project. For example this can be handy to communicate, for HTML id's, tempfiles etc.

通常，我所做的是计算字符串的CRC16，添加总和并返回它。

In general, what I do is calculate a CRC16 of a string, add the sum and return it.

例如，这两个字符串生成相同的id（数字）：

For example, these two strings generate the same id (number):

o.uniqueId( 'M:/Mijn Muziek/Various Artists/Revs & ElBee - Tell It To My Heart.mp3' );
o.uniqueId( 'M:/Mijn Muziek/Various Artists/Dwight Yoakam - The Back Of Your Hand.Mp3');

它们都生成一个224904的id。

They both generates an id of 224904.

以下示例是一个javascript示例。我的问题是，我怎样才能避免（稍微改变）它产生重复？ （如果您可能想知道'o。'的含义，它是这些函数所属的对象）：

The following example is a javascript example. My question is, how can i avoid (with a little change) that it generates a duplicate? (In case you might wonder what 'o.' means, it is the object where these functions belongs to):

o.getCrc16 = function(s, bSumPos) {
  if(typeof s !== 'string' || s.length === 0) {
    return 0;
  }
  var crc = 0xFFFF,
    L = s.length,
    sum = 0,
    x = 0,
    j = 0;
  for(var i = 0; i < L; i++) {
    j = s.charCodeAt(i);
    sum += ((i + 1) * j);
    x = ((crc >> 8) ^ j) & 0xFF;
    x ^= x >> 4;
    crc = ((crc << 8) ^ (x << 12) ^ (x << 5) ^ x) & 0xFFFF;
  }
  return crc + ((bSumPos ? 1 : 0) * sum);
}
o.uniqueId = function(s, bres) {
  if(s == undefined || typeof s != 'string') {
    if(!o.___uqidc) {
      o.___uqidc = 0;
    } else {
      ++o.___uqidc;
    }
    var od = new Date(),
      i = s = od.getTime() + '' + o.___uqidc;
  } else {
    var i = o.getCrc16(s, true);
  }
  return((bres) ? 'res:' : '') + (i + (i ? s.length : 0));
};

如何使用代码稍作更改来避免重复？

How can I avoid duplicates with use of a little change to the code?

推荐答案

好的，做了大量的测试并且来了。由以下内容生成的相对较短的唯一ID：

All right, did allot of testing and come to this. A relative short unique id generated by the following:

o.lz = function(i,c)
{
  if( typeof c != 'number' || c <= 0 || (typeof i != 'number' && typeof i != 'string') )
   { return i; }
  i+='';

  while( i.length < c )
   { i='0'+i; }
  return i;  
}

o.getHashCode = function(s)
{
 var hash=0,c=(typeof s == 'string')?s.length:0,i=0;
 while(i<c) 
 {
   hash = ((hash<<5)-hash)+s.charCodeAt(i++);
   //hash = hash & hash; // Convert to 32bit integer
 }

 return ( hash < 0 )?((hash*-1)+0xFFFFFFFF):hash; // convert to unsigned
}; 

o.uniqueId = function( s, bres )
{ 
  if( s == undefined || typeof s != 'string' )
  { 
     if( !o.___uqidc )
      { o.___uqidc=0; }
     else { ++o.___uqidc; } 
     var od = new Date(),
         i = s = od.getTime()+''+o.___uqidc; 
  }
  else { var i = o.getHashCode( s ); }
  return ((bres)?'res:':'')+i.toString(32)+'-'+o.lz((s.length*4).toString(16),3);  
};

示例：

o.uniqueId( 'M:/Mijn Muziek/Various Artists/Revs & ElBee - Tell It To My Heart.mp3' );
o.uniqueId( 'M:/Mijn Muziek/Various Artists/Dwight Yoakam - The Back Of Your Hand.Mp3');

将产生以下ID：

dh8qi9t-114
je38ugg-120

对于我目的似乎是足够独特，额外的长度增加了一些独特性。在大约40.000个mp3文件的文件系统上进行测试，但没有发现任何碰撞。

For my purpose it seems to be unique enough, also the extra length adds some more uniqueness. Test it on filesystem with approx 40.000 mp3 files and did not found any collision.

如果您认为这不是可行的方法，请告诉我。

If you think this is not the way to go, please let me know.

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