EventStore File Formats

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Key File Format

The Key File consists of a header and a series of records. The Key File stores indices into structured data files. Outside libraries are used to read the files. All information is stored in 32 bit unsigned words.

File header

The header contains identifying information and the number of records in the file.

number of words purpose of field
1 Format/Endian identifier: 2718281*256 + version number of file format
1 unique file identifier
1 number of events in file


Record

A record consists of a run,event number pair that identifies the event, and its offset into the file.

number of words purpose of field
1 Run number
1 Event number
1 uid of file containing the event
1 "stream"/event type (currently unused)
2 Index of event into data file

Index notes:

  • For HDDM files, the index is the record number in the file
  • For EVIO files, the index is an offset into the file, in units of 4-bytes words