commit 0d300334a4647a4da31d25f84ffbc5fb06e5a942
author Hector Dearman <hjd@google.com> Wed Nov 22 11:05:34 2017 +0000
committer Hector Dearman <hjd@google.com> Wed Nov 22 11:05:34 2017 +0000
tree 83fd2eb0bd8aed8885e09fab8512d981963ee4a2
parent a47036d3cef814db755ad8e8a2c5dc3c9cbbe7a6

Ftrace: Refactor the public interface

The new flow is as follows:

The caller creates:
 FtraceController (does all the initialization)
 FtraceConfig (tells us which events they are interested in)
 FtraceSink::Delegate (implements the client callbacks)

Then they use FtraceController#CreateSink with the FtraceConfig
and Delegate to create a FtraceSink. While the FtraceSink lives
we know to listen and parse the events in config. We turn the
config into an EventFilter and stash it on the FtraceSink
(the EventFilter allows for efficient testing of whether an
event is enabled).

Next they call FtraceController#Start to tell us to start
watching the raw pipe fds.

When we see data at one of those pipes we call
Delgate#GetBundleForCpu to get a protozero object we can write
into. We pass this object and the EventFilter to the CpuReader.
The CpuReader grabs pages from the pipe, parses them, then uses
the EventFilter to write only the enabled events into the
protozero object. After the write we call Delgate#OnBundleComplete
so the client can do any needed bookkeeping.

Finally after some time the client can call FtraceController#Stop
at which point we stop listening for data at the pipes.

Other small changes:
1) Move FtraceCpuReader to src/ (since it is no longer public).
2) Various name shuffling:
FtraceToProtoTranslationTable -> ProtoTranslationTable
FtraceCpuReader -> CpuReader
3) Moving all methods dealing with paths/reading/writing debugfs
into their own class: FtraceApi.

Change-Id: I1fcb725096d2dd5d094ebd2cc5d44691e7b6cca2