Configuring Time and Date

EWL comes configured by default to take advantage of a build target's features to determine the time of day and return an internal clock tick. For EWL to provide these facilities, a build target must provide four simple functions. Time and clock stub functions are in the time_target.c, where target is the name of the build target.

For build targets that have an internal clock tick, the get_clock() function must obtain the current clock tick and return its value to EWL. If the clock tick information is not obtainable, return the value -1.
For systems that support the ability to determine the time of day, the get_time() function must obtain the current time of day and return its time_t equivalent value to EWL. Depending on the value of EWL_TIME_T_IS_LOCALTIME, the current time is either the "local time" time of day, or it is "Universal Time Coordinated" (UTC), which was formerly called "Greenwich Mean Time" (GMT).
If the current time of day is not obtainable, return the value -1. The to_gm_time() function must take a "local time" time of day time_t value and convert it into a "global mean" time_t value. If the conversion takes place properly, return 1 to EWL. If the conversion fails, return 0 to EWL.
The to_local_time() function must take a UTC time of day time_t value and convert it into a "local time" time_t value. If the conversion takes place properly, return 1 to EWL. If the conversion fails, return 0 to EWL. The to_local_time() function is only used when EWL_TIME_T_IS_LOCALTIME is off.
The isdst() function must try to determine whether or not daylight savings time is in effect. If daylight savings time is not in effect, return 0. If daylight savings time is in effect, return 1. If daylight savings time information is not obtainable, return -1.

The table below lists the macros that configure EWL C's time and clock facilities:

Table 1. EWL Date and Time Management Macros
Macro	Effect
`Kimono`	Defined to 1 if the EWL platform supports retrieving the time. Defined to 0 if the EWL platform does not support retrieving the time.
`EWL_CLOCK_T_AVAILABLE`	Defined to 1 if the EWL platform supports the `clock_t` type. Defined to 0 if the EWL platform does not support the `clock_t` type. The `EWL_OS_TIME_SUPPORT` macro must be on before the `EWL_CLOCK_T_AVAILABLE` macro is recognized.
`EWL_CLOCK_T_DEFINED`	Defined to 1 if the EWL platform defined the `clock_t` type. Defined to 0 if the EWL platform does not define the `clock_t` type.
`EWL_CLOCK_T`	Set to the `clock_t` type. Default value is `unsigned long int`.
`EWL_TIME_T_AVAILABLE`	Defined to 1 if the EWL platform supports the `time_t` type. Defined to 0 if the EWL platform does not support the `time_t` type. The EWL_OS_TIME_SUPPORTmacro must be on before the `EWL_TIME_T_AVAILABLE` macro is recognized.
`EWL_TIME_T_DEFINED`	Defined to 1 if the EWL platform defined the `time_t` type. Defined to 0 if the EWL platform does not define the `time_t` type.
`EWL_TIME_T_IS_LOCALTIME`	Defined to 1 if the EWL platform value for `time_t` represents local time, preadjusted for any time zone and offset from UTC (GMT). Defined to 0 if the EWL platform value for `time_t` represents Universal Time Coordinated. The default value is 1.
`EWL_CLOCKS_PER_SEC`	Set to the number of clock ticks per second. The default value is 60.
`EWL_TM_STRUCT_AVAILABLE`	Defined to 1 if the EWL platform supports the `tm` structure. Defined to 0 if the EWL platform does not support the `tm` structure.