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How to generate an uniqe number always?

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How to generate an uniqe number always?

 
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  #1
Nov 22nd, 2008
Hi ,

can any one tell me how to generate an unique number ?
this can be done in C# with great ease. But i wonder how to generate tat in c++
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Re: How to generate an uniqe number always?

 
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Nov 22nd, 2008
C++ Syntax (Toggle Plain Text) 
  1. int getUnique() {
  2.   static int n = 0;
  3.   return ++n;
  4. }

This function is not multithreading safe.
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Re: How to generate an uniqe number always?

 
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Nov 22nd, 2008
>this can be done in C# with great ease
Oh good. Show us how you do it in C# so we know what the hell you're talking about by a "unique number".
I'm here to prove you wrong.
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Re: How to generate an uniqe number always?

 
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Nov 22nd, 2008
C++ Syntax (Toggle Plain Text) 
  1.             Console.WriteLine(System.Guid.NewGuid().ToString());
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Re: How to generate an uniqe number always?

 
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Nov 22nd, 2008
There is no such thing as a truly unique number, especially in computing. The seed is generally the time.
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Re: How to generate an uniqe number always?

 
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Nov 22nd, 2008
http://msdn.microsoft.com/en-us/libr...stem.guid.aspx

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A GUID is a 128-bit integer (16 bytes) that can be used across all computers and networks wherever a unique identifier is required. Such an identifier has a very low probability of being duplicated.
How low of a probability are you looking for?
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Re: How to generate an uniqe number always?

 
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  #7
Nov 22nd, 2008
i am storing some data in the database,
for tat i always need to send a unique value to it,
if the value already exists then an exception will be thrown.
so when ever i am storing in the db the value have to be unique.
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Re: How to generate an uniqe number always?

 
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Nov 22nd, 2008
Start your "unique number" at 1 and increment it for each new data record. That seems to be the easiest and safest way to make all your numbers unique.
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Re: How to generate an uniqe number always?

 
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  #9
Nov 23rd, 2008
What if i run the program again, then again it starts with 1,
so i would get a exception
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Re: How to generate an uniqe number always?

 
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Nov 23rd, 2008
then start at a value 1 more than the highest in the dB, if you wish to use incrementing type indexes. Or you could use the number of microseconds since (e.g.) 12:00am jan 1900 UTC as your 'unique number'.
Last edited by dougy83; Nov 23rd, 2008 at 2:39 am.
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