getNumberOfEvents changes the internal state of the file

[jstrube]

• OS version: SLC6, Ubuntu 18.04
• Compiler version: GCC 6.2, gcc 7.4
• Package version: v02-12-01
• Reproduced by: call readNextEvent(), followed by getNumberOfEvents(), followed by readNextEvent(). You have just read the same event twice!
• Goal: It is not obvious that getNumberOfEvents leads to this behavior, nor should it. The name suggest that this is a getter method. However, it looks like the implementation changes the internal state of the file.
  Tested on /pnfs/desy.de/ilc/prod/ilc/mc-opt-3/ild/dst-merged/500-TDR_ws/2f_Z_hadronic/ILD_l5_o1_v02/v02-00-01/rv02-00-01.sv02-00-01.mILD_l5_o1_v02.E500-TDR_ws.I250114.P2f_z_h.eL.pR.n033.d_dstm_10410_96.slcio

[rete]

Thanks for reporting this.
Indeed, calling getNumberOfEvents() is doing the following:

• ask the random access manager to read the index at the end of the file
• populate the event map
• reset the stream pointer to begin
  This is why you read twice the same event I guess

[gaede]

I agree that this seems not obvious - should change the documentation.