On 18/07/2019 11:28, Ravindra Kumar Meena wrote:
I would use two structures for this in C, one for the compact header
and
one for the large header. I would not use bit fields in C.
Without bit fields how I would assign it exact 27-bit timestamp?
You open the C book that you already organized and have a look into the
chapter that introduces integers and operators.
It is mentioned on https://diamon.org/ctf/#ex-variants that we can use
union in C for variant data-type.
Yes, but the union will not help you much at the producer side. Either
the event has a compact header or a long header. The event id determines
which header variant is used. At least this is how I understood this. I
may be wrong.
In metadata enum in header_compact is defined like this:
enum : uint5_t { compact = 0 ... 30, extended = 31 } id;
It has two members. The compact members has range from 0 to 31 but we
can't define range in enum members in C
Don't use an enum. Just build up the 32-bit integer from the two parts,
the 5-bit id and the 27-bit timestampl.
You have to figure out how the 27-bit timestamp works. It must relative
to some reference point.
I looked into the Trace Compass example. The content in the binary file
is formatted as follow:
<magic><uuid><stream_id><stream_instance_id><packet_context>
This much we have already achieved.
Now
< 8-bit data. It is always in 31( 1F )>
This is probably the event id 32 part.
<32-bit event_id> <64-bit
timestamp> <event_fields>
This looks like the large header.
Now after this
<32-bit data> <event_fields> again <32-bit data> <event_fields> agina <
32-bit data> <event_fields> ....
I am not able to understand what this <32-bit data> is between every
<event_fields>
I guess this is the event-specific payload.
How is the id used? We are interested in the sched_switch events.
Okay
--
*Ravindra Kumar Meena*,
B. Tech. Computer Science and Engineering,
Indian Institute of Technology (Indian School of Mines)
<https://www.iitism.ac.in/>, Dhanbad
--
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