/*
     This file is part of GNUnet.
     (C) 2001-2013 Christian Grothoff (and other contributing authors)

     GNUnet is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published
     by the Free Software Foundation; either version 3, or (at your
     option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/

/**
 * @file include/gnunet_time_lib.h
 * @brief functions related to time
 * @author Christian Grothoff
 * @defgroup time Time and time calculations
 * @{
 */

#ifndef GNUNET_TIME_LIB_H
#define GNUNET_TIME_LIB_H

#ifdef __cplusplus
extern "C"
{
#if 0                           /* keep Emacsens' auto-indent happy */
}
#endif
#endif

#include "gnunet_common.h"

/**
 * Time for absolute times used by GNUnet, in microseconds.
 */
struct GNUNET_TIME_Absolute
{
  /**
   * The actual value.
   */
  uint64_t abs_value_us;
};

/**
 * Time for relative time used by GNUnet, in microseconds.
 * Always positive, so we can only refer to future time.
 */
struct GNUNET_TIME_Relative
{
  /**
   * The actual value.
   */
  uint64_t rel_value_us;
};

GNUNET_NETWORK_STRUCT_BEGIN

/**
 * Time for relative time used by GNUnet, in microseconds and in network byte order.
 */
struct GNUNET_TIME_RelativeNBO
{
  /**
   * The actual value (in network byte order).
   */
  uint64_t rel_value_us__ GNUNET_PACKED;
};


/**
 * Time for absolute time used by GNUnet, in microseconds and in network byte order.
 */
struct GNUNET_TIME_AbsoluteNBO
{
  /**
   * The actual value (in network byte order).
   */
  uint64_t abs_value_us__ GNUNET_PACKED;
};
GNUNET_NETWORK_STRUCT_END

/**
 * Relative time zero.
 */
#define GNUNET_TIME_UNIT_ZERO     GNUNET_TIME_relative_get_zero_()

/**
 * Absolute time zero.
 */
#define GNUNET_TIME_UNIT_ZERO_ABS GNUNET_TIME_absolute_get_zero_()

/**
 * One microsecond, our basic time unit.
 */
#define GNUNET_TIME_UNIT_MICROSECONDS GNUNET_TIME_relative_get_unit_()

/**
 * One millisecond.
 */
#define GNUNET_TIME_UNIT_MILLISECONDS GNUNET_TIME_relative_get_millisecond_()

/**
 * One second.
 */
#define GNUNET_TIME_UNIT_SECONDS GNUNET_TIME_relative_get_second_()

/**
 * One minute.
 */
#define GNUNET_TIME_UNIT_MINUTES GNUNET_TIME_relative_get_minute_()

/**
 * One hour.
 */
#define GNUNET_TIME_UNIT_HOURS   GNUNET_TIME_relative_get_hour_()

/**
 * One day.
 */
#define GNUNET_TIME_UNIT_DAYS    GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_HOURS,   24)

/**
 * One week.
 */
#define GNUNET_TIME_UNIT_WEEKS   GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_DAYS,     7)

/**
 * One month (30 days).
 */
#define GNUNET_TIME_UNIT_MONTHS  GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_DAYS,    30)

/**
 * One year (365 days).
 */
#define GNUNET_TIME_UNIT_YEARS   GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_DAYS,   365)

/**
 * Constant used to specify "forever".  This constant
 * will be treated specially in all time operations.
 */
#define GNUNET_TIME_UNIT_FOREVER_REL GNUNET_TIME_relative_get_forever_ ()

/**
 * Constant used to specify "forever".  This constant
 * will be treated specially in all time operations.
 */
#define GNUNET_TIME_UNIT_FOREVER_ABS GNUNET_TIME_absolute_get_forever_ ()



/**
 * Threshold after which exponential backoff should not increase (15 m).
 */
#define GNUNET_TIME_STD_EXPONENTIAL_BACKOFF_THRESHOLD GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 15)


/**
 * Perform our standard exponential back-off calculation, starting at 1 ms
 * and then going by a factor of 2 up unto a maximum of 15 m.
 *
 * @param r current backoff time, initially zero
 */
#define GNUNET_TIME_STD_BACKOFF(r) GNUNET_TIME_relative_min (GNUNET_TIME_STD_EXPONENTIAL_BACKOFF_THRESHOLD, \
   GNUNET_TIME_relative_multiply (GNUNET_TIME_relative_max (GNUNET_TIME_UNIT_MILLISECONDS, (r)), 2));

/**
 * Return relative time of 0ms.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_zero_ (void);


/**
 * Return absolute time of 0ms.
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_get_zero_ (void);


/**
 * Return relative time of 1 microsecond.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_unit_ (void);


/**
 * Return relative time of 1ms.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_millisecond_ (void);


/**
 * Return relative time of 1s.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_second_ (void);


/**
 * Return relative time of 1 minute.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_minute_ (void);


/**
 * Return relative time of 1 hour.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_hour_ (void);


/**
 * Return "forever".
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_get_forever_ (void);


/**
 * Return "forever".
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_get_forever_ (void);


/**
 * Get the current time.
 *
 * @return the current time
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_get (void);


/**
 * Convert relative time to an absolute time in the
 * future.
 *
 * @param rel relative time to convert
 * @return timestamp that is "rel" in the future, or FOREVER if rel==FOREVER (or if we would overflow)
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_relative_to_absolute (struct GNUNET_TIME_Relative rel);


/**
 * Return the minimum of two relative time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is smaller
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_min (struct GNUNET_TIME_Relative t1,
                          struct GNUNET_TIME_Relative t2);



/**
 * Return the maximum of two relative time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is larger
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_max (struct GNUNET_TIME_Relative t1,
                          struct GNUNET_TIME_Relative t2);


/**
 * Return the minimum of two absolute time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is smaller
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_min (struct GNUNET_TIME_Absolute t1,
                          struct GNUNET_TIME_Absolute t2);


/**
 * Return the maximum of two absolute time values.
 *
 * @param t1 first timestamp
 * @param t2 other timestamp
 * @return timestamp that is smaller
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_max (struct GNUNET_TIME_Absolute t1,
                          struct GNUNET_TIME_Absolute t2);


/**
 * Given a timestamp in the future, how much time
 * remains until then?
 *
 * @param future some absolute time, typically in the future
 * @return future - now, or 0 if now >= future, or FOREVER if future==FOREVER.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_absolute_get_remaining (struct GNUNET_TIME_Absolute future);


/**
 * Calculate the estimate time of arrival/completion
 * for an operation.
 *
 * @param start when did the operation start?
 * @param finished how much has been done?
 * @param total how much must be done overall (same unit as for "finished")
 * @return remaining duration for the operation,
 *        assuming it continues at the same speed
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_calculate_eta (struct GNUNET_TIME_Absolute start, uint64_t finished,
                           uint64_t total);


/**
 * Compute the time difference between the given start and end times.
 * Use this function instead of actual subtraction to ensure that
 * "FOREVER" and overflows are handeled correctly.
 *
 * @param start some absolute time
 * @param end some absolute time (typically larger or equal to start)
 * @return 0 if start >= end; FOREVER if end==FOREVER; otherwise end - start
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_absolute_get_difference (struct GNUNET_TIME_Absolute start,
                                     struct GNUNET_TIME_Absolute end);


/**
 * Get the duration of an operation as the
 * difference of the current time and the given start time "hence".
 *
 * @param whence some absolute time, typically in the past
 * @return aborts if hence==FOREVER, 0 if hence > now, otherwise now-hence.
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_absolute_get_duration (struct GNUNET_TIME_Absolute whence);


/**
 * Add a given relative duration to the
 * given start time.
 *
 * @param start some absolute time
 * @param duration some relative time to add
 * @return FOREVER if either argument is FOREVER or on overflow; start+duration otherwise
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_add (struct GNUNET_TIME_Absolute start,
                          struct GNUNET_TIME_Relative duration);


/**
 * Subtract a given relative duration from the
 * given start time.
 *
 * @param start some absolute time
 * @param duration some relative time to subtract
 * @return ZERO if start <= duration, or FOREVER if start time is FOREVER; start-duration otherwise
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_subtract (struct GNUNET_TIME_Absolute start,
                               struct GNUNET_TIME_Relative duration);


/**
 * Multiply relative time by a given factor.
 *
 * @param rel some duration
 * @param factor integer to multiply with
 * @return FOREVER if rel=FOREVER or on overflow; otherwise rel*factor
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_multiply (struct GNUNET_TIME_Relative rel,
                               unsigned int factor);


/**
 * Divide relative time by a given factor.
 *
 * @param rel some duration
 * @param factor integer to divide by
 * @return FOREVER if rel=FOREVER or factor==0; otherwise rel/factor
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_divide (struct GNUNET_TIME_Relative rel,
                             unsigned int factor);


/**
 * Add relative times together.
 *
 * @param a1 some relative time
 * @param a2 some other relative time
 * @return FOREVER if either argument is FOREVER or on overflow; a1+a2 otherwise
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_add (struct GNUNET_TIME_Relative a1,
                          struct GNUNET_TIME_Relative a2);


/**
 * Subtract relative timestamp from the other.
 *
 * @param a1 first timestamp
 * @param a2 second timestamp
 * @return ZERO if a2>=a1 (including both FOREVER), FOREVER if a1 is FOREVER, a1-a2 otherwise
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_subtract (struct GNUNET_TIME_Relative a1,
                               struct GNUNET_TIME_Relative a2);


/**
 * Convert relative time to network byte order.
 *
 * @param a time to convert
 * @return converted time value
 */
struct GNUNET_TIME_RelativeNBO
GNUNET_TIME_relative_hton (struct GNUNET_TIME_Relative a);


/**
 * Convert relative time from network byte order.
 *
 * @param a time to convert
 * @return converted time value
 */
struct GNUNET_TIME_Relative
GNUNET_TIME_relative_ntoh (struct GNUNET_TIME_RelativeNBO a);


/**
 * Convert relative time to network byte order.
 *
 * @param a time to convert
 * @return converted time value
 */
struct GNUNET_TIME_AbsoluteNBO
GNUNET_TIME_absolute_hton (struct GNUNET_TIME_Absolute a);


/**
 * Convert relative time from network byte order.
 *
 * @param a time to convert
 * @return converted time value
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_absolute_ntoh (struct GNUNET_TIME_AbsoluteNBO a);


/**
 * Set the timestamp offset for this instance.
 *
 * @param offset the offset to skew the locale time by
 */
void
GNUNET_TIME_set_offset (long long offset);


/**
 * Get the timestamp offset for this instance.
 *
 * @return the offset we currently skew the locale time by
 */
long long
GNUNET_TIME_get_offset (void);


/**
 * Return the current year (i.e. '2011').
 */
unsigned int
GNUNET_TIME_get_current_year (void);


/**
 * Convert a year to an expiration time of January 1st of that year.
 *
 * @param year a year (after 1970, please ;-)).
 * @return absolute time for January 1st of that year.
 */
struct GNUNET_TIME_Absolute
GNUNET_TIME_year_to_time (unsigned int year);


/**
 * Convert an expiration time to the respective year (rounds)
 *
 * @param at absolute time
 * @return year a year (after 1970), 0 on error
 */
unsigned int
GNUNET_TIME_time_to_year (struct GNUNET_TIME_Absolute at);


#if 0                           /* keep Emacsens' auto-indent happy */
{
#endif
#ifdef __cplusplus
}
#endif

/** @} */ /* end of group time */


/* ifndef GNUNET_TIME_LIB_H */
#endif
/* end of gnunet_time_lib.h */
