Modify function from localtime to localtime_r

[zondatw]

Sometimes user want to display log which about time, but in following example, it will get wrong time, because localtime doc says:

The returned value points to an internal object whose validity or value may be altered by any subsequent call to gmtime or localtime."

, maybe change function to localtime_r is a good way.

In this example, it will get the current time, but I hope it's getting 2021/01/01 00:00:00

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#include "log/src/log.h"

#define DATETIME_BUF_SIZE 0xff
#define DATETIME_FORMAT "%Y/%m/%d %H:%M:%S"

int get_datetime(time_t timestamp, char* datetime) {
  struct tm *local;

  local = localtime(&timestamp);
  log_info("Current sec: %d", local->tm_sec);
  log_info("Current min: %d", local->tm_min);
  log_info("Current hour: %d", local->tm_hour);
  log_info("Current mday: %d", local->tm_mday);
  log_info("Current mon: %d", local->tm_mon + 1);
  log_info("Current year: %d", local->tm_year + 1900);
  log_info("Current wday: %d", local->tm_wday);
  log_info("Current yday: %d", local->tm_yday);

  strftime(datetime, DATETIME_BUF_SIZE, DATETIME_FORMAT, local);
  return 0;
}

int main() {
  time_t timestamp = 1609430400; // 2021/01/01 00:00:00
  char datetime[DATETIME_BUF_SIZE];

  get_datetime(timestamp, datetime);
  log_info("Display datetime: %s\n", datetime);
  return 0;
}