UID from dicom.UID.generate_uid() may not be unique if called twice in rapid succession

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What steps will reproduce the problem?
1. Call dicom.UID.generate_uid() twice in two subsequent calls

What is the expected output? What do you see instead?
- I expect that uids are different. What I see, is that the UIDs may actually 
be identical.

What version of the product are you using?
- pydicom 0.9.8

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Please provide any additional information below.
- The dicom.UID.generate_uid() should include some kind of counter that is 
incremented between successive calls.

Original issue reported on code.google.com by jog...@gmail.com on 2 Apr 2013 at 1:25

[GoogleCodeExporter]

I had a quick look at this. The UID includes the time, and the smallest 
resolution is microseconds. Apparently that is not fast enough. There are a few 
possible paths:
- base the UID on something else, but a finer time resolution could probably 
hit the same problem 
- update documentation to note the microsecond issue ... if the calling code 
needs multiple UIDs "at once", then it could get one and add its own suffixes 
to create the others
- add a counter in the generate_UID code as suggested in the submitted issue. 
There is already code, though, to optionally truncate if the UID becomes too 
long, and I'm not sure if that limit might be hit.
- additionally, could add an optional argument to return a specific number of 
UIDs as a tuple. Then the code could simply increment the microseconds on the 
first one (not increasing the length)... and store the last one to ensure that 
subsequent calls started later than that

Anyone have ideas on these or other options?

Original comment by darcymason@gmail.com on 5 Apr 2013 at 12:53

• Changed state: Accepted