[kernel][kservice] add rt_gmtime_r api

include/rtthread.h

@@ -473,6 +473,7 @@ rt_int32_t rt_vsprintf(char *dest, const char *format, va_list arg_ptr);
 rt_int32_t rt_vsnprintf(char *buf, rt_size_t size, const char *fmt, va_list args);
 rt_int32_t rt_sprintf(char *buf, const char *format, ...);
 rt_int32_t rt_snprintf(char *buf, rt_size_t size, const char *format, ...);
+struct tm *rt_gmtime_r(const time_t *timep, struct tm *result);
 
 #if defined(RT_USING_DEVICE) && defined(RT_USING_CONSOLE)
 rt_device_t rt_console_set_device(const char *name);

src/kservice.c

@@ -1177,6 +1177,61 @@ void rt_kprintf(const char *fmt, ...)
 RTM_EXPORT(rt_kprintf);
 #endif
 
+struct tm *rt_gmtime_r(const time_t *timep, struct tm *result)
+{
+#define IS_LEAP_YEAR(year) (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0))
+
+    const rt_uint32_t mon_table[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+    rt_uint32_t year = 1970, month = 0;
+    rt_uint32_t daycount = 0, second = 0, number = 0;
+
+    second = *timep % (24 * 60 * 60);
+    result->tm_hour = second / 3600;
+    result->tm_min = (second % 3600) / 60;
+    result->tm_sec = (second % 3600) % 60;
+
+    daycount = *timep / (24 * 60 * 60);
+    result->tm_wday = (daycount + 4) % 7;
+    if (daycount != 0)
+    {
+        while (daycount >= 365)
+        {
+            number = IS_LEAP_YEAR(year) ? 366 : 365;
+            if (daycount >= number)
+            {
+                daycount -= number;
+                year++;
+            }
+            else
+                break;
+        }
+        result->tm_year = year - 1900;
+
+        while (daycount >= 28)
+        {
+            if (month == 1 && IS_LEAP_YEAR(year))
+            {
+                if (daycount >= 29)
+                    daycount -= 29;
+                else
+                    break;
+            }
+            else
+            {
+                if (daycount >= mon_table[month])
+                    daycount -= mon_table[month];
+                else
+                    break;
+            }
+            month++;
+        }
+        result->tm_mon = month + 1;
+        result->tm_mday = daycount + 1;
+    }
+    return result;
+}
+RTM_EXPORT(rt_gmtime_r);
+
 #ifdef RT_USING_HEAP
 /**
  * This function allocates a memory block, which address is aligned to the