Filter that takes as input a stream of flattened event fragments and produces as output a set of EVB_FRAGMENT ring items. This is intended to be in the middle of a pipeline that begins with the event orderer part of the event builder and ends with an instance of stdintoring. Used in that way it allows event fragments to be observed by monitoring programs prior to being sent to the event builder via a pipeline that begins with ringtostdout piped into eventbuilder.
See INPUT FORMAT for more information about the shape of a flattened event segment, the required input. See DataFormat.h and the structure of EventBuilderFragment ring item.
As a filter, the input stream comes from stdin and the output is directed to stdout. As previously mentioned, this allows the program to be used as an element of a unix pipeline of commands.
The input format recognized by this program is a flattened fragment. This consists of a fragment header followed immediately by the fragment payload.
The fragment header is defined by the data type EVB::FragmentHeader described in fragment.h. It looks like this:
struct EVB::FragmentHeader {
uint64_t s_timestamp;
uint32_t s_sourceId;
uint32_t s_size;
uint32_t s_barrier;
};
Where the fields in this struture have the following meaning:
uint64_t s_timestamp;
The timestamp that indicates the creation time of the fragment.
uint32_t s_sourceId;
The id of the source of the data.
uint32_t s_size;
The number of bytes of payload data. In a flattened fragment the payload of the fragment immediately follows this struct.
uint32_t s_barrier;
If non-zero the fragment is an element of a barrier. Barrier fragments are divisions in the ordering process so that all elements of a barrier received prior to timeout will be emitted consecutively. A barrier event is supposed to provide contributions from all data sources. Examples of barrier fragments are end of run indications.