text: // Copyright 2007 - 2021, Alan Antonuk and the rabbitmq-c contributors.
  // SPDX-License-Identifier: mit
  
  #ifndef AMQP_TIMER_H
  #define AMQP_TIMER_H
  
  #include <stdint.h>
  
  #if ((defined(_WIN32)) || (defined(__MINGW32__)) || (defined(__MINGW64__)))
  #ifndef WINVER
  #define WINVER 0x0502
  #endif
  #ifndef WIN32_LEAN_AND_MEAN
  #define WIN32_LEAN_AND_MEAN
  #endif
  #include <winsock2.h>
  #else
  #include <sys/time.h>
  #endif
  
  #define AMQP_MS_PER_S 1000
  #define AMQP_US_PER_MS 1000
  #define AMQP_NS_PER_S 1000000000
  #define AMQP_NS_PER_MS 1000000
  #define AMQP_NS_PER_US 1000
  
  /* This represents a point in time in reference to a monotonic clock.
   *
   * The internal representation is ns, relative to the monotonic clock.
   *
   * There are two 'special' values:
   * - 0: means 'this instant', its meant for polls with a 0-timeout, or
   *   non-blocking option
   * - UINT64_MAX: means 'at infinity', its mean for polls with an infinite
   *   timeout
   */
  typedef struct amqp_time_t_ {
    uint64_t time_point_ns;
  } amqp_time_t;
  
  /* Gets a monotonic timestamp. This will return 0 if the underlying call to the
   * system fails.
   */
  uint64_t amqp_get_monotonic_timestamp(void);
  
  /* Get a amqp_time_t that is timeout from now.
   * If timeout is NULL, an amqp_time_infinite() is created.
   *
   * Returns AMQP_STATUS_OK on success.
   * AMQP_STATUS_INVALID_PARAMETER if timeout is invalid
   * AMQP_STATUS_TIMER_FAILURE if the underlying call to get the current timestamp
   * fails.
   */
  int amqp_time_from_now(amqp_time_t *time, const struct timeval *timeout);
  
  /* Get a amqp_time_t that is seconds from now.
   * If seconds <= 0, then amqp_time_infinite() is created.
   *
   * Returns AMQP_STATUS_OK on success.
   * AMQP_STATUS_TIMER_FAILURE if the underlying call to get the current timestamp
   * fails.
   */
  int amqp_time_s_from_now(amqp_time_t *time, int seconds);
  
  /* Create an infinite amqp_time_t */
  amqp_time_t amqp_time_infinite(void);
  
  /* Gets the number of ms until the amqp_time_t, suitable for the timeout
   * parameter in poll().
   *
   * -1 will be returned for amqp_time_infinite values.
   * 0 will be returned for amqp_time_immediate values.
   * AMQP_STATUS_TIMEOUT will be returned if time was in the past.
   * AMQP_STATUS_TIMER_FAILURE will be returned if the underlying call to get the
   * current timestamp fails.
   */
  int amqp_time_ms_until(amqp_time_t time);
  
  /* Gets a timeval filled in with the time until amqp_time_t. Suitable for the
   * parameter in select().
   *
   * The in parameter specifies a storage location for *out.
   * If time is an inf timeout, then *out = NULL.
   * If time is a 0-timeout or the timer has expired, then *out = {0, 0}
   * Otherwise *out is set to the time left on the time.
   *
   * AMQP_STATUS_OK will be returned if successfully filled.
   * AMQP_STATUS_TIMER_FAILURE is returned when the underlying call to get the
   * current timestamp fails.
   */
  int amqp_time_tv_until(amqp_time_t time, struct timeval *in,
                         struct timeval **out);
  
  /* Test whether current time is past the provided time.
   *
   * TODO: this isn't a great interface to use. Fix this.
   *
   * Return AMQP_STATUS_OK if time has not past
   * Return AMQP_STATUS_TIMEOUT if time has past
   * Return AMQP_STATUS_TIMER_FAILURE if the underlying call to get the current
   * timestamp fails.
   */
  int amqp_time_has_past(amqp_time_t time);
  
  /* Return the time value that happens first */
  amqp_time_t amqp_time_first(amqp_time_t l, amqp_time_t r);
  
  int amqp_time_equal(amqp_time_t l, amqp_time_t r);
  #endif /* AMQP_TIMER_H */
  