/*
 * Copyright (c) 2003-2005, Raphael Manfredi
 *
 *----------------------------------------------------------------------
 * This file is part of gtk-gnutella.
 *
 *  gtk-gnutella 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 2 of the License, or
 *  (at your option) any later version.
 *
 *  gtk-gnutella 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 gtk-gnutella; if not, write to the Free Software
 *  Foundation, Inc.:
 *      59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *----------------------------------------------------------------------
 */

/**
 * @ingroup lib
 * @file
 *
 * Time manipulation and caching routines.
 *
 * @author Raphael Manfredi
 * @date 2003-2005
 */

#ifndef _tm_h_
#define _tm_h_

#include "common.h"

/**
 * tm_zero
 *
 * Returns true if time is zero.
 */
#define tm_zero(t)	((t)->tv_sec == 0 && (t)->tv_usec == 0)

/**
 * tm2f
 *
 * Convert timeval description into floating point representation.
 */
#define tm2f(t)		((double) (t)->tv_sec + (t)->tv_usec / 1000000.0)

/**
 * tm2ms
 *
 * Convert timeval description into milliseconds.
 */
#define tm2ms(t)	((t)->tv_sec * 1000 + (t)->tv_usec / 1000)

/**
 * tm2us
 *
 * Convert timeval description into microseconds.
 */
#define tm2us(t)	((t)->tv_sec * 1000000 + (t)->tv_usec)

typedef GTimeVal tm_t;

void tm_init(void);
void f2tm(double t, tm_t *tm);
void tm_elapsed(tm_t *elapsed, const tm_t *t1, const tm_t *t0);
void tm_sub(tm_t *tm, const tm_t *dec);
void tm_add(tm_t *tm, const tm_t *inc);
int tm_cmp(const tm_t *a, const tm_t *b);

void tm_now(tm_t *tm);
void tm_now_exact(tm_t *tm);
time_t tm_time_exact(void);
double tm_cputime(double *user, double *sys);

guint tm_hash(gconstpointer key);
int tm_equal(gconstpointer a, gconstpointer b);

/*
 * We use the direct difference of time_t values instead of difftime()
 * for performance. Just in case there is any system which requires difftime()
 * e.g. if time_t is BCD-encoded, define USE_DIFFTIME.
 */
#if defined(USE_DIFFTIME)
typedef gint64 time_delta_t;

static inline time_delta_t
delta_time(time_t t1, time_t t0)
{
	return difftime(t1, t0);
}
#else	/* !USE_DIFFTIME */
typedef time_t time_delta_t;

static inline ALWAYS_INLINE time_delta_t
delta_time(time_t t1, time_t t0)
{
	return t1 - t0;
}

static inline void
time_t_check(void)
{
	/* If time_t is not a signed integer type, we cannot calculate properly
	 * with the raw values. Define USE_DIFFTIME, if this check fails.*/
	STATIC_ASSERT((time_t) -1 < 0);
}
#endif /* USE_DIFFTIME*/

#define TIME_DELTA_T_MAX	MAX_INT_VAL(time_delta_t)

/**
 * Advances the given timestamp by delta using saturation arithmetic.
 * @param t the timestamp to advance.
 * @param delta the amount of seconds to advance.
 * @return the advanced timestamp or TIME_T_MAX.
 */
static inline time_t
time_advance(time_t t, gulong delta)
{
	/* Using time_t for delta and TIME_T_MAX instead of INT_MAX
	 * would be cleaner but give a confusing interface. Jumping 136
	 * years in time should be enough for everyone. Most systems
	 * don't allow us to advance a time_t beyond 2038 anyway.
	 */

	do {
		long d;

		d = MIN(delta, (gulong) LONG_MAX);
		if (d >= TIME_T_MAX - t) {
			t = TIME_T_MAX;
			break;
		}
		t += d;
		delta -= d;
	} while (delta > 0);

	return t;
}

/**
 * Add delta to a time_delta_t, saturating towards TIME_DELTA_T_MAX.
 */
static inline time_delta_t
time_delta_add(time_delta_t td, gulong delta)
{
	do {
		long d;

		d = MIN(delta, (gulong) LONG_MAX);
		if (d >= TIME_DELTA_T_MAX - td) {
			td = TIME_DELTA_T_MAX;
			break;
		}
		td += d;
		delta -= d;
	} while (delta > 0);

	return td;
}

/*
 * Convenience routines.
 */

/**
 * Computes the elapsed time (t1 - t0) and return duration in seconds, as
 * a floating point quantity to represent sub-seconds.
 */
static inline double
tm_elapsed_f(const tm_t *t1, const tm_t *t0)
{
	tm_t elapsed;

	tm_elapsed(&elapsed, t1, t0);
	return tm2f(&elapsed);
}

/**
 * Computes the elapsed time (t1 - t0) and return duration in milliseconds.
 */
static inline time_delta_t
tm_elapsed_ms(const tm_t *t1, const tm_t *t0)
{
	tm_t elapsed;

	tm_elapsed(&elapsed, t1, t0);
	return tm2ms(&elapsed);
}

/**
 * Computes the elapsed time (t1 - t0) and return duration in microseconds.
 */
static inline time_delta_t
tm_elapsed_us(const tm_t *t1, const tm_t *t0)
{
	tm_t elapsed;

	tm_elapsed(&elapsed, t1, t0);
	return tm2us(&elapsed);
}

extern tm_t tm_cached_now;			/* Currently cached time */

/**
 * Get current time, at the second granularity (cached).
 */
static inline time_t
tm_time(void)
{
	return (time_t) tm_cached_now.tv_sec;
}

tm_t tm_start_time(void);

/**
 * Returns the current time relative to the startup time (cached).
 *
 * @note For convenience unsigned long is used, so that we can
 *		 always cast them to pointers and back again. The guaranteed
 *		 width of 32-bit should be sufficient for session duration.
 *		 Where this is unsufficient, stick to time_t.
 */
static inline unsigned long
tm_relative_time(void)
{
	return delta_time(tm_time(), tm_start_time().tv_sec);
}
#endif /* _tm_h_ */

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