UUID ToString Algorithm

thejez · **Posted:** Fri Jul 08, 2005 12:37 pm

I was reading the NHibernate docs:

Section 3.1.4.4 wrote:

The UUID is generated by calling Guid.NewGuid().ToByteArray() and then converting the byte[] into a char[]. The char[] is returned as a String consisting of 16 characters.

A few questions:
1. Why use ToByteArray etc... and not .ToString("N") ?? seems like ToString would be faster
2. Why 16 chars and not the full 32 ?? Using 16 makes comparing guids visually somewhat difficult since most of the time you'll be looking at 32 caracters. Granted, I hope to never have to visually compare these - but when writing test cases I would have to do the same ToByteArray junk just to get a working test....

thejez · **Posted:** Fri Jul 08, 2005 2:59 pm

Well i just went ahead and changed the UUIDStringGenerator.cs file to make it work how I think it should:

Code:

public object Generate( ISessionImplementor session, object obj )
{
//   byte[ ] guidInBytes = new byte[16];
//   StringBuilder guidBuilder = new StringBuilder( 16, 16 );
//
//   guidInBytes = Guid.NewGuid().ToByteArray();
//
//   // add each item in Byte[] to the string builder
//   for( int i = 0; i < guidInBytes.Length; i++ )
//   {
//      guidBuilder.Append( ( char ) guidInBytes[ i ] );
//   }

   return Guid.NewGuid().ToString("N");
}

I'm still curious as to the whole byte[] and 16 char thing though....

KPixel · **Posted:** Sun Jul 10, 2005 10:11 am

Hello thejez,

Can you create a JIRA issue (http://jira.nhibernate.org) so that we can investigate on it later? :)

As this implementation (probably) comes from Hibernate; it is possible that Java don't have a Guid.ToString("N")...
We just need to make sure that they are functionally equivalents.

thejez · **Joined:** Sun Jul 10, 2005 6:30 pm **Posts:** 10

Well, they are functional equivalents, although they do not return the same length string... but that shouldn't matter too much.

I went ahead and added it as an improvment to jira as you suggested.

http://jira.nhibernate.org/browse/NH-331