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/*

* call-seq:

* Process.clock_getres(clock_id [, unit]) -> number

*

* Returns a time resolution returned by POSIX clock_getres() function.

*

* +clock_id+ specifies a kind of clock.

* See the document of +Process.clock_gettime+ for details.

*

* +clock_id+ can be a symbol as +Process.clock_gettime+.

* However the result may not be accurate.

* For example, +Process.clock_getres(:SUS_GETTIMEOFDAY_BASED_CLOCK_REALTIME, :nanosecond)+

* returns 1000, always.

*

* If the given +clock_id+ is not supported, Errno::EINVAL is raised.

*

* +unit+ specifies a type of the return value.

* +Process.clock_getres+ accepts +unit+ as +Process.clock_gettime+.

* The default value, +:float_second+, is also same as

* +Process.clock_gettime+.

*

* +Process.clock_getres+ also accepts +:hertz+ as +unit+.

* +:hertz+ means a the reciprocal of +:float_second+.

*

* +:hertz+ can be used to obtain the exact value of

* the clock ticks per second for times() function and

* CLOCK_PER_SEC for clock() function.

*

* +Process.clock_getres(:POSIX_TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID, :hertz)+

* returns the clock ticks per second.

*

* +Process.clock_getres(:ISO_C_CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID, :hertz)+

* returns CLOCK_PER_SEC.

*

* p Process.clock_getres(Process::CLOCK_MONOTONIC)

* #=> 1.0e-09

*

*/

VALUE

rb_clock_getres(int argc, VALUE *argv)

{

struct timespec ts;

VALUE clk_id, unit;

int ret;

double hertz;

rb_scan_args(argc, argv, "11", &clk_id, &unit);

if (SYMBOL_P(clk_id)) {

#ifdef RUBY_SUS_GETTIMEOFDAY_BASED_CLOCK_REALTIME

if (clk_id == RUBY_SUS_GETTIMEOFDAY_BASED_CLOCK_REALTIME) {

ts.tv_sec = 0;

ts.tv_nsec = 1000;

goto success;

}

#endif

#ifdef RUBY_ISO_C_TIME_BASED_CLOCK_REALTIME

if (clk_id == RUBY_ISO_C_TIME_BASED_CLOCK_REALTIME) {

ts.tv_sec = 1;

ts.tv_nsec = 0;

goto success;

}

#endif

#ifdef RUBY_SUS_GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID

if (clk_id == RUBY_SUS_GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID) {

ts.tv_sec = 0;

ts.tv_nsec = 1000;

goto success;

}

#endif

#ifdef RUBY_POSIX_TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID

if (clk_id == RUBY_POSIX_TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID) {

hertz = get_clk_tck();

goto success_hertz;

}

#endif

#ifdef RUBY_ISO_C_CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID

if (clk_id == RUBY_ISO_C_CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID) {

hertz = CLOCKS_PER_SEC;

goto success_hertz;

}

#endif

#ifdef RUBY_MACH_ABSOLUTE_TIME_BASED_CLOCK_MONOTONIC

/* not yet */

#endif

}

else {

#if defined(HAVE_CLOCK_GETTIME)

clockid_t c;

c = NUM2CLOCKID(clk_id);

ret = clock_getres(c, &ts);

if (ret == -1)

rb_sys_fail("clock_getres");

goto success;

#endif

}

/* EINVAL emulates clock_getres behavior when clock_id is invalid. */

errno = EINVAL;

rb_sys_fail(0);

success_hertz:

if (unit == ID2SYM(rb_intern("hertz"))) {

return DBL2NUM(hertz);

}

else {

double ns;

ns = 1e9 / hertz;

ts.tv_sec = (time_t)(ns*1e-9);

ts.tv_nsec = ns - ts.tv_sec*1e9;

return make_clock_result(&ts, unit);

}

success:

if (unit == ID2SYM(rb_intern("hertz"))) {

hertz = 1e9 / (ts.tv_sec * 1e9 + ts.tv_nsec);

return DBL2NUM(hertz);

}

else {

return make_clock_result(&ts, unit);

}

}

rb_define_module_function(rb_mProcess, "clock_getres", rb_clock_getres, -1);