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You can reduce the size and improve the efficiency of your
code by creating an event and adding items to it in a single step,
using the varargs (variable-length argument list) version of the create function. You can add items to an existing event
efficiently by using the varargs version of the item-set function. Example 4-2 “Using Variable-Length
Argument Lists” introduces
the following functions:
EvmEventCreateVa — Creates
an event, and supplies item names and values in a single call. For
more information about this function, see EvmEventCreateVa(3). EvmItemSetVa — Sets
data item values in the event. The list of items and variables to
be supplied is the same as that supplied for EvmEventCreateVa.
For more information about this function, see EvmItemSetVa(3).
Example 4-2 Using Variable-Length
Argument Lists |
#include <stdio.h>#include <evm/evm.h>int main(){ EvmEvent_t event;EvmItemValue_t itemval_name, itemval_priority; /* Each item you include in EvmEventCreateVa() function must have an identifier and a value, and the argument list must be terminated with an EvmITEM_NONE identifier. *//* NOTE: To store the values of standard data items in an event, they should first be stored in a variable of type EvmItemValue_t which is an union whose definition can be found in /usr/include/evm/evm.h */ /* NOTE: EvmItemValue_t is an union, so you will have to use different variables to store different items, otherwise they will be overwritten */ itemval_name.NAME = "sys.unix.evm"; itemval_priority.PRIORITY = 200; EvmEventCreateVa(&event, EvmITEM_NAME, itemval_name, EvmITEM_PRIORITY, itemval_priority, EvmITEM_NONE); /* The varargs version of EvmItemSetva() uses the same style of argument list as EvmEventCreateVa(). In this example, items that are already present in the event are being added, so the new values just replace the old ones. */ itemval_name.NAME = "sys.unix.evm.mark"; itemval_priority.PRIORITY = 100; EvmItemSetVa(event,EvmITEM_NAME, itemval_name, EvmITEM_PRIORITY, itemval_priority, EvmITEM_NONE); /* You can easily include variable data item in a varargs list by using the EvmITEM_VAR_Xxx item identifier, where Xxx is the type of the variable. If you include a variable in this way, it is very important that you follow the identifier with the correct number of arguments to describe the variable. You must always supply two further arguments: a string containing the name of the variable, and a value argument. The type of the value argument depends on the type of the variable b in this example, the first variable requires a string and the second requires an integer. Certain types of variable require an additional argument - see EvmItemSet (3) for more details.*/ EvmItemSetVa(event, EvmITEM_VAR_UINT16,"exit_code",17, EvmITEM_VAR_STRING,"progname","my_app", EvmITEM_NONE); /* The call to EvmEventDump() displays a formatted dump of the event on stdout, to demonstrate that the expected data items and variables have been added correctly. */ EvmEventDump(event,stdout); /* When you have finished with the event, free the storage space the event uses. */ EvmEventDestroy(event); } |
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