How to read array value with Channel Access compound data types

["Wang, Lin via Tech-talk" <tech-talk at aps.anl.gov>]

Dear all, From Channel Access tutorial and EPICS base source code, I have learned that besides simple data types like DBR_INT and DBR_STRING, Channel Access client can also read data using compound data types like DBR_TIME_INT and DBR_TIME_STRING. My

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Dear all,

From Channel Access tutorial and EPICS base source code, I have learned that besides simple data types like DBR_INT and DBR_STRING, Channel Access client can also read data using compound data types like DBR_TIME_INT and DBR_TIME_STRING.

My understanding is that the data will be returned in dbr field of event_handler_args structure,

typedef struct event_handler_args {

    void            *usr;   /* user argument supplied with request */

    chanId          chid;   /* channel id */

    long            type;   /* the type of the item returned */

    long            count;  /* the element count of the item returned */

    const void      *dbr;   /* a pointer to the item returned */

    int             status; /* ECA_XXX status of the requested op from the server */

} evargs;

And the data returned for DBR_TIME_STRING compound data type is dbr_time_string structure,

struct dbr_time_string{

    dbr_short_t status;         /* status of value */

    dbr_short_t severity;       /* severity of alarm */

    epicsTimeStamp  stamp;          /* time stamp */

    dbr_string_t    value;          /* current value */

};

However, the value field of dbr_time_string structure is a scalar value instead of array or pointer, which means that only the first item of the array can be read. Therefore, my question is, how do I read array value from records like waveform with the compound data type?

Thanks,

Lin