text: /* Copyright JS Foundation and other contributors, http://js.foundation
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #define _BSD_SOURCE
  #include <stdarg.h>
  #include <stdlib.h>
  #include <sys/time.h>
  
  #include "jerry-core/include/jerryscript-port.h"
  
  #include "us_ticker_api.h"
  
  #ifndef JSMBED_OVERRIDE_JERRY_PORT_LOG
  /**
   * Provide log message implementation for the engine.
   */
  void
  jerry_port_log (jerry_log_level_t level, /**< log level */
                  const char *format, /**< format string */
                  ...)  /**< parameters */
  {
    (void) level; /* ignore log level */
  
    va_list args;
    va_start (args, format);
    vfprintf (stderr, format, args);
    va_end (args);
  
    if (strlen (format) == 1 && format[0] == 0x0a) /* line feed (\n) */
    {
      printf ("\r"); /* add CR for proper display in serial monitors */
    }
  } /* jerry_port_log */
  #endif /* JSMBED_OVERRIDE_JERRY_PORT_LOG */
  
  /**
   * Implementation of jerry_port_get_local_time_zone_adjustment.
   *
   * @return 0, as we live in UTC.
   */
  double
  jerry_port_get_local_time_zone_adjustment (double unix_ms, bool is_utc)
  {
    return 0;
  } /* jerry_port_get_local_time_zone_adjustment */
  
  /**
   * Implementation of jerry_port_get_current_time.
   *
   * @return current timer's counter value in milliseconds
   */
  double
  jerry_port_get_current_time (void)
  {
    static uint64_t last_tick = 0;
    static time_t last_time = 0;
    static uint32_t skew = 0;
  
    uint64_t curr_tick = us_ticker_read (); /* The value is in microseconds. */
    time_t curr_time = time(NULL); /*  The value is in seconds. */
    double result = curr_time * 1000;
  
    /* The us_ticker_read () has an overflow for each UINT_MAX microseconds
     * (~71 mins). For each overflow event the ticker-based clock is about 33
     * milliseconds fast. Without a timer thread the milliseconds part of the
     * time can be corrected if the difference of two get_current_time calls
     * are within the mentioned 71 mins. Above that interval we can assume
     * that the milliseconds part of the time is negligibe.
     */
    if (curr_time - last_time > (time_t)(((uint32_t)-1) / 1000000)) {
      skew = 0;
    } else if (last_tick > curr_tick) {
      skew = (skew + 33) % 1000;
    }
    result += (curr_tick / 1000 - skew) % 1000;
  
    last_tick = curr_tick;
    last_time = curr_time;
    return result;
  } /* jerry_port_get_current_time */
  