// host_clock.c
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <mach/mach.h>
#include <mach/clock.h>
#define OUT_ON_MACH_ERROR(msg, retval) if (kr != KERN_SUCCESS) { mach_error(msg ":" , kr); goto out; }
int
main()
{
kern_return_t kr;
host_name_port_t myhost;
clock_serv_t clk_system, clk_calendar, clk_realtime;
natural_t attribute[4];
mach_msg_type_number_t count;
mach_timespec_t timespec;
struct timeval t;
myhost = mach_host_self();
// Get a send right to the system clock‘s name port
kr = host_get_clock_service(myhost, SYSTEM_CLOCK,
(clock_serv_t *)&clk_system);
OUT_ON_MACH_ERROR("host_get_clock_service", kr);
// Get a send right to the calendar clock‘s name port
kr = host_get_clock_service(myhost, CALENDAR_CLOCK,
(clock_serv_t *)&clk_calendar);
OUT_ON_MACH_ERROR("host_get_clock_service", kr);
// Get a send right to the real-time clock‘s name port
kr = host_get_clock_service(myhost, REALTIME_CLOCK,
(clock_serv_t *)&clk_realtime);
OUT_ON_MACH_ERROR("host_get_clock_service", kr);
//// System clock
count = sizeof(attribute)/sizeof(natural_t);
// Get the clock‘s resolution in nanoseconds
kr = clock_get_attributes(clk_system, CLOCK_GET_TIME_RES,
(clock_attr_t)attribute, &count);
OUT_ON_MACH_ERROR("clock_get_attributes", kr);
// Get the current time
kr = clock_get_time(clk_system, ×pec);
OUT_ON_MACH_ERROR("clock_get_time", kr);
printf("System clock : %u s + %u ns (res %u ns)\n",
timespec.tv_sec, timespec.tv_nsec, attribute[0]);
//// Real-time clock
count = sizeof(attribute)/sizeof(natural_t);
kr = clock_get_attributes(clk_realtime, CLOCK_GET_TIME_RES,
(clock_attr_t)&attribute, &count);
OUT_ON_MACH_ERROR("clock_get_attributes", kr);
kr = clock_get_time(clk_realtime, ×pec);
OUT_ON_MACH_ERROR("clock_get_time", kr);
printf("Realtime clock: %u s + %u ns (res %u ns)\n",
timespec.tv_sec, timespec.tv_nsec, attribute[0]);
//// Calendar clock
count = sizeof(attribute)/sizeof(natural_t);
kr = clock_get_attributes(clk_calendar, CLOCK_GET_TIME_RES,
(clock_attr_t)&attribute, &count);
OUT_ON_MACH_ERROR("clock_get_attributes", kr);
kr = clock_get_time(clk_calendar, ×pec);
gettimeofday(&t, NULL);
OUT_ON_MACH_ERROR("clock_get_time", kr);
printf("Calendar clock: %u s + %u ns (res %u ns)\n",
timespec.tv_sec, timespec.tv_nsec, attribute[0]);
printf("gettimeofday : %ld s + %d us\n", t.tv_sec, t.tv_usec);
out:
// Should deallocate ports here for cleanliness
mach_port_deallocate(mach_task_self(), myhost);
mach_port_deallocate(mach_task_self(), clk_calendar);
mach_port_deallocate(mach_task_self(), clk_system);
mach_port_deallocate(mach_task_self(), clk_realtime);
exit(0);
}
haidragondeMacBook-Air:6-2 haidragon$ ls
host_clock.c
haidragondeMacBook-Air:6-2 haidragon$ gcc -Wall -o host_clock host_clock.c
host_clock.c:28:5: warning: variable ‘clk_calendar‘ is used uninitialized whenever ‘if‘ condition is
true [-Wsometimes-uninitialized]
OUT_ON_MACH_ERROR("host_get_clock_service", kr);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
host_clock.c:10:9: note: expanded from macro ‘OUT_ON_MACH_ERROR‘
if (kr != KERN_SUCCESS) { mach_error(msg ":" , kr); goto out; }
^~~~~~~~~~~~~~~~~~
host_clock.c:78:44: note: uninitialized use occurs here
mach_port_deallocate(mach_task_self(), clk_calendar);
^~~~~~~~~~~~
host_clock.c:28:5: note: remove the ‘if‘ if its condition is always false
OUT_ON_MACH_ERROR("host_get_clock_service", kr);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
host_clock.c:10:5: note: expanded from macro ‘OUT_ON_MACH_ERROR‘
if (kr != KERN_SUCCESS) { mach_error(msg ":" , kr); goto out; }
^
host_clock.c:17:52: note: initialize the variable ‘clk_calendar‘ to silence this warning
clock_serv_t clk_system, clk_calendar, clk_realtime;
^
= 0
host_clock.c:33:5: warning: variable ‘clk_realtime‘ is used uninitialized whenever ‘if‘ condition is
true [-Wsometimes-uninitialized]
OUT_ON_MACH_ERROR("host_get_clock_service", kr);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
host_clock.c:10:9: note: expanded from macro ‘OUT_ON_MACH_ERROR‘
if (kr != KERN_SUCCESS) { mach_error(msg ":" , kr); goto out; }
^~~~~~~~~~~~~~~~~~
host_clock.c:80:44: note: uninitialized use occurs here
mach_port_deallocate(mach_task_self(), clk_realtime);
^~~~~~~~~~~~
host_clock.c:33:5: note: remove the ‘if‘ if its condition is always false
OUT_ON_MACH_ERROR("host_get_clock_service", kr);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
host_clock.c:10:5: note: expanded from macro ‘OUT_ON_MACH_ERROR‘
if (kr != KERN_SUCCESS) { mach_error(msg ":" , kr); goto out; }
^
host_clock.c:28:5: warning: variable ‘clk_realtime‘ is used uninitialized whenever ‘if‘ condition is
true [-Wsometimes-uninitialized]
OUT_ON_MACH_ERROR("host_get_clock_service", kr);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
host_clock.c:10:9: note: expanded from macro ‘OUT_ON_MACH_ERROR‘
if (kr != KERN_SUCCESS) { mach_error(msg ":" , kr); goto out; }
^~~~~~~~~~~~~~~~~~
host_clock.c:80:44: note: uninitialized use occurs here
mach_port_deallocate(mach_task_self(), clk_realtime);
^~~~~~~~~~~~
host_clock.c:28:5: note: remove the ‘if‘ if its condition is always false
OUT_ON_MACH_ERROR("host_get_clock_service", kr);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
host_clock.c:10:5: note: expanded from macro ‘OUT_ON_MACH_ERROR‘
if (kr != KERN_SUCCESS) { mach_error(msg ":" , kr); goto out; }
^
host_clock.c:17:66: note: initialize the variable ‘clk_realtime‘ to silence this warning
clock_serv_t clk_system, clk_calendar, clk_realtime;
^
= 0
3 warnings generated.
haidragondeMacBook-Air:6-2 haidragon$ ls
host_clock host_clock.c
haidragondeMacBook-Air:6-2 haidragon$ ./host_clock
System clock : 20035 s + 406693924 ns (res 10000000 ns)
Realtime clock: 20035 s + 406780101 ns (res 10000000 ns)
Calendar clock: 1562077197 s + 706757784 ns (res 10000000 ns)
gettimeofday : 1562077197 s + 706766 us
haidragondeMacBook-Air:6-2 haidragon$ 原文地址：https://blog.51cto.com/haidragon/2416418