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Process.clock_getres
static VALUE
rb_clock_getres(int argc, VALUE *argv, VALUE _)
{
struct timetick tt;
timetick_int_t numerators[2];
timetick_int_t denominators[2];
int num_numerators = 0;
int num_denominators = 0;
VALUE unit = (rb_check_arity(argc, 1, 2) == 2) ? argv[1] : Qnil;
VALUE clk_id = argv[0];
if (SYMBOL_P(clk_id)) {
#ifdef RUBY_GETTIMEOFDAY_BASED_CLOCK_REALTIME
if (clk_id == RUBY_GETTIMEOFDAY_BASED_CLOCK_REALTIME) {
tt.giga_count = 0;
tt.count = 1000;
denominators[num_denominators++] = 1000000000;
goto success;
}
#endif
#ifdef RUBY_TIME_BASED_CLOCK_REALTIME
if (clk_id == RUBY_TIME_BASED_CLOCK_REALTIME) {
tt.giga_count = 1;
tt.count = 0;
denominators[num_denominators++] = 1000000000;
goto success;
}
#endif
#ifdef RUBY_TIMES_BASED_CLOCK_MONOTONIC
if (clk_id == RUBY_TIMES_BASED_CLOCK_MONOTONIC) {
tt.count = 1;
tt.giga_count = 0;
denominators[num_denominators++] = get_clk_tck();
goto success;
}
#endif
#ifdef RUBY_GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID
if (clk_id == RUBY_GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID) {
tt.giga_count = 0;
tt.count = 1000;
denominators[num_denominators++] = 1000000000;
goto success;
}
#endif
#ifdef RUBY_TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID
if (clk_id == RUBY_TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID) {
tt.count = 1;
tt.giga_count = 0;
denominators[num_denominators++] = get_clk_tck();
goto success;
}
#endif
#ifdef RUBY_CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID
if (clk_id == RUBY_CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID) {
tt.count = 1;
tt.giga_count = 0;
denominators[num_denominators++] = CLOCKS_PER_SEC;
goto success;
}
#endif
#ifdef RUBY_MACH_ABSOLUTE_TIME_BASED_CLOCK_MONOTONIC
if (clk_id == RUBY_MACH_ABSOLUTE_TIME_BASED_CLOCK_MONOTONIC) {
const mach_timebase_info_data_t *info = get_mach_timebase_info();
tt.count = 1;
tt.giga_count = 0;
numerators[num_numerators++] = info->numer;
denominators[num_denominators++] = info->denom;
denominators[num_denominators++] = 1000000000;
goto success;
}
#endif
}
else {
#if defined(HAVE_CLOCK_GETRES)
struct timespec ts;
clockid_t c = NUM2CLOCKID(clk_id);
int ret = clock_getres(c, &ts);
if (ret == -1)
rb_sys_fail("clock_getres");
tt.count = (int32_t)ts.tv_nsec;
tt.giga_count = ts.tv_sec;
denominators[num_denominators++] = 1000000000;
goto success;
#endif
}
/* EINVAL emulates clock_getres behavior when clock_id is invalid. */
rb_syserr_fail(EINVAL, 0);
success:
if (unit == ID2SYM(id_hertz)) {
return timetick2dblnum_reciprocal(&tt, numerators, num_numerators, denominators, num_denominators);
}
else {
return make_clock_result(&tt, numerators, num_numerators, denominators, num_denominators, unit);
}
}
Returns an estimate of the resolution of a clock_id using the POSIX clock_getres() function.
Note the reported resolution is often inaccurate on most platforms due to underlying bugs for this function and therefore the reported resolution often differs from the actual resolution of the clock in practice. Inaccurate reported resolutions have been observed for various clocks including CLOCK_MONOTONIC and CLOCK_MONOTONIC_RAW when using Linux, macOS, BSD or AIX platforms, when using ARM processors, or when using virtualization.
clock_id specifies a kind of clock. See the document of Process.clock_gettime for details. clock_id can be a symbol as for Process.clock_gettime.
If the given clock_id is not supported, Errno::EINVAL is raised.
unit specifies the type of the return value. Process.clock_getres accepts unit as Process.clock_gettime. The default value, :float_second, is also the same as Process.clock_gettime.
Process.clock_getres also accepts :hertz as unit. :hertz means the reciprocal of :float_second.
:hertz can be used to obtain the exact value of the clock ticks per second for the times() function and CLOCKS_PER_SEC for the clock() function.
Process.clock_getres(:TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID, :hertz) returns the clock ticks per second.
Process.clock_getres(:CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID, :hertz) returns CLOCKS_PER_SEC.
p Process.clock_getres(Process::CLOCK_MONOTONIC) #=> 1.0e-09