DOKK / manpages / debian 11 / libpcp3-dev / pmUnpackHighResEventRecords.3.en
PMUNPACKEVENTRECORDS(3) Library Functions Manual PMUNPACKEVENTRECORDS(3)

pmUnpackEventRecords, pmUnpackHighResEventRecords - unpack event records

#include <pcp/pmapi.h>

int pmUnpackEventRecords(pmValueSet *vsp, int idx, pmResult ***rap);

int pmUnpackHighResEventRecords(pmValueSet *vsp, int idx, pmHighResResult ***hrap);

cc ... -lpcp

Event records are encoded as a packed array of records within a pmResult using a container metric with a value of type PM_TYPE_EVENT , and a pmHighResResult when using a metric of type PM_TYPE_HIGHRES_EVENT.

pmUnpackEventRecords and pmUnpackHighResEventRecords may be used to unpack event records from a metric value identified by vsp and idx. If the metric has a singular value, idx should be 0, else the ordinal instance value identified by idx will be unpacked, i.e. vsp->vlist[idx]. The unpacked records are turned into either pmResult or pmHighResResult structures, one per event record and one metric per event parameter, and rap is returned as a pointer to an array (NULL pointer terminated) of pointers to the result structures.

The only difference between the two result types is the timestamp scale; the pmHighResResult allows for nanosecond precision, whereas pmResult allows for microsecond resolution.

Some control information from the packed event records is unpacked into additional ``anonymous'' metrics as follows:

1.
If the event record has a non-zero flags value, then the corresponding pmResult/pmHighResResult will have the flags value encoded with the additional metric event.flags that is inserted ahead of all other event parameters.
2.
If the event record flag is set to PM_EVENT_FLAG_MISSED, then the corresponding pmResult/pmHighResResult will have one metric event.missed with a value that equals the number of event records ``missed'' because either the PMDA could not keep up, or the PMAPI client did not collect the event records fast enough.

pmUnpackEventRecords returns the number of pmResult structures as the return value, which is >= 0 for success. Similarly, pmUnpackHighResEventRecords returns the number of pmHighResResult structures as the return value, which is >= 0 for success.

rap and the associated pmResult structures may be freed using the convenience function pmFreeEventResult(3).

Similarly, the hrap and the associated pmHighResResult structures may be freed using the convenience function pmFreeHighResEventResult.

The following errors are possible:

The values associated with vsp are not encoded using the format PM_VAL_DPTR or PM_VAL_SPTR, or the flags at the head of the event record has an unexpected value.
The value associated with vsp is not singular as expected.
vsp is not a value of type PM_TYPE_EVENT.
The value identified by vbp is not legal because the value length is less than the minimum size, or the number of event records encoded in the (value header) pmEventArray/pmEventHighResArray structure is negative, or the number of missed event records in the array is negative.
Either vsp indicates more than one value is present (all the event records are expected to be packed in a single metric value), or when unpacking the event records, the processing continues past the end of the enclosing value. Indicates corruption of the packed event record.
Event parameters must have one of the arithmetic types, else PM_TYPE_AGGREGATE, PM_TYPE_STRING or PM_TYPE_AGGREGATE_STATIC.
refer to pmErrStr(3).

PMAPI(3) and pmFreeEventResult(3).

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