zclock(3)
=========

NAME
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zclock - millisecond clocks and delays

SYNOPSIS
--------
----
//  This is a stable class, and may not change except for emergencies. It
//  is provided in stable builds.
//  Sleep for a number of milliseconds
CZMQ_EXPORT void
    zclock_sleep (int msecs);

//  Return current system clock as milliseconds. Note that this clock can  
//  jump backwards (if the system clock is changed) so is unsafe to use for
//  timers and time offsets. Use zclock_mono for that instead.             
CZMQ_EXPORT int64_t
    zclock_time (void);

//  Return current monotonic clock in milliseconds. Use this when you compute
//  time offsets. The monotonic clock is not affected by system changes and  
//  so will never be reset backwards, unlike a system clock.                 
CZMQ_EXPORT int64_t
    zclock_mono (void);

//  Return current monotonic clock in microseconds. Use this when you compute
//  time offsets. The monotonic clock is not affected by system changes and  
//  so will never be reset backwards, unlike a system clock.                 
CZMQ_EXPORT int64_t
    zclock_usecs (void);

//  Return formatted date/time as fresh string. Free using zstr_free().
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT char *
    zclock_timestr (void);

//  Self test of this class.
CZMQ_EXPORT void
    zclock_test (bool verbose);

----

DESCRIPTION
-----------

The zclock class provides essential sleep and system time functions,
used to slow down threads for testing, and calculate timers for polling.
Wraps the non-portable system calls in a simple portable API.

The Win32 Sleep() call defaults to 16ms resolution unless the system
timer resolution is increased with a call to timeBeginPeriod() permitting
1ms granularity.

EXAMPLE
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.From zclock_test method
----
int64_t start = zclock_time ();
zclock_sleep (10);
assert ((zclock_time () - start) >= 10);
start = zclock_mono ();
int64_t usecs = zclock_usecs ();
zclock_sleep (10);
assert ((zclock_mono () - start) >= 10);
assert ((zclock_usecs () - usecs) >= 10000);
char *timestr = zclock_timestr ();
if (verbose)
    puts (timestr);
free (timestr);
----
