`filewriter`: `runlog/icp_event`

首先追踪 filewriter 如何消费底层事件数据流，以及它当前如何写入 runlog 组。将提议的 newStyle 命令与 Mantid 所说明的解析行为进行比较，然后验证 START_COLLECTION、STOP_COLLECTION、CHANGE 和 CHANGE_PERIOD 是否反映良好/不良的 frame 和 period 转换；在认为工作完成之前，确定是否需要包含 ABORT。

The filewriter must be able to write the runlog/icp_event group, as parts of this are currently parsed by Mantid.

From discussions, my current understanding is that Mantid:

• Does read CHANGE_PERIOD and CHANGE events. We will emulate these by looking at the event data stream and emitting a fake CHANGE_PERIOD message each time we see incoming data with a different period number.
• Does read START_COLLECTION, STOP_COLLECTION, ABORT messages.
• Can read BEGIN, RESUME, END_SE_WAIT, PAUSE, END, ABORT, UPDATE, START_SE_WAIT messages, but only if oldStyle is being used.
• Does not parse the numbers from GF x RF x GUAH x messages.

Potential differences from existing files

• Proposal is to only write the newStyle commands, so START_COLLECTION, STOP_COLLECTION, CHANGE, CHANGE_PERIOD, ABORT.
• All data will be emulated (derived from the underlying event data):
  • START_COLLECTION written at the beginning, and then on any transition from a bad frame to a good frame.
  • STOP_COLLECTION written on any transition from a good frame to a bad frame, and then at the end.
  • ABORT - not convinced this is meaningful, if the run is aborted then won't get a .nxs file at all...
  • CHANGE_PERIOD will be written any time we get a frame which has a different period than the most-recently-seen frame
• CHANGE_PERIOD will account for hardware periods as well as software periods (they look the same to the filewriter in the streaming system). This means that there could be a much higher frequency of CHANGE_PERIOD events than previously.
• START_COLLECTION and STOP_COLLECTION will account for hardware vetos as well as pause/runcontrol (they look the same to the filewriter in the streaming system). This means that there could be a much higher frequency of START_COLLECTION and STOP_COLLECTION events than previously.