// SPDX-License-Identifier: LGPL-2.1+
/*
 * Copyright (C) 2018 Red Hat, Inc.
 */

#include "nm-default.h"

#include "nm-time-utils.h"

#include "nm-logging-fwd.h"

/*****************************************************************************/

typedef struct {
	/* the offset to the native clock, in seconds. */
	gint64 offset_sec;
	clockid_t clk_id;
} GlobalState;

static const GlobalState *volatile p_global_state;

static const GlobalState *
_t_init_global_state (void)
{
	static GlobalState global_state = { };
	static gsize init_once = 0;
	const GlobalState *p;
	clockid_t clk_id;
	struct timespec tp;
	gint64 offset_sec;
	int r;

	clk_id = CLOCK_BOOTTIME;
	r = clock_gettime (clk_id, &tp);
	if (r == -1 && errno == EINVAL) {
		clk_id = CLOCK_MONOTONIC;
		r = clock_gettime (clk_id, &tp);
	}

	/* The only failure we tolerate is that CLOCK_BOOTTIME is not supported.
	 * Other than that, we rely on kernel to not fail on this. */
	g_assert (r == 0);
	g_assert (tp.tv_nsec >= 0 && tp.tv_nsec < NM_UTILS_NS_PER_SECOND);

	/* Calculate an offset for the time stamp.
	 *
	 * We always want positive values, because then we can initialize
	 * a timestamp with 0 and be sure, that it will be less then any
	 * value nm_utils_get_monotonic_timestamp_*() might return.
	 * For this to be true also for nm_utils_get_monotonic_timestamp_s() at
	 * early boot, we have to shift the timestamp to start counting at
	 * least from 1 second onward.
	 *
	 * Another advantage of shifting is, that this way we make use of the whole 31 bit
	 * range of signed int, before the time stamp for nm_utils_get_monotonic_timestamp_s()
	 * wraps (~68 years).
	 **/
	offset_sec = (- ((gint64) tp.tv_sec)) + 1;

	if (!g_once_init_enter (&init_once)) {
		/* there was a race. We expect the pointer to be fully initialized now. */
		p = g_atomic_pointer_get (&p_global_state);
		g_assert (p);
		return p;
	}

	global_state.offset_sec = offset_sec;
	global_state.clk_id = clk_id;
	p = &global_state;
	g_atomic_pointer_set (&p_global_state, p);
	g_once_init_leave (&init_once, 1);

	_nm_utils_monotonic_timestamp_initialized (&tp,
	                                           p->offset_sec,
	                                           p->clk_id == CLOCK_BOOTTIME);

	return p;
}

#define _t_get_global_state() \
	({ \
		const GlobalState *_p; \
		\
		_p = g_atomic_pointer_get (&p_global_state); \
		(G_LIKELY (_p) ? _p : _t_init_global_state ()); \
	})

#define _t_clock_gettime_eval(p, tp) \
	({ \
		struct timespec *const _tp = (tp); \
		const GlobalState *const _p2 = (p); \
		int _r; \
		\
		nm_assert (_tp); \
		\
		_r = clock_gettime (_p2->clk_id, _tp); \
		\
		nm_assert (_r == 0); \
		nm_assert (_tp->tv_nsec >= 0 && _tp->tv_nsec < NM_UTILS_NS_PER_SECOND); \
		\
		_p2; \
	})

#define _t_clock_gettime(tp) \
	_t_clock_gettime_eval (_t_get_global_state (), tp);

/*****************************************************************************/

/**
 * nm_utils_get_monotonic_timestamp_ns:
 *
 * Returns: a monotonically increasing time stamp in nanoseconds,
 * starting at an unspecified offset. See clock_gettime(), %CLOCK_BOOTTIME.
 *
 * The returned value will start counting at an undefined point
 * in the past and will always be positive.
 *
 * All the nm_utils_get_monotonic_timestamp_*s functions return the same
 * timestamp but in different scales (nsec, usec, msec, sec).
 **/
gint64
nm_utils_get_monotonic_timestamp_ns (void)
{
	const GlobalState *p;
	struct timespec tp;

	p = _t_clock_gettime (&tp);

	/* Although the result will always be positive, we return a signed
	 * integer, which makes it easier to calculate time differences (when
	 * you want to subtract signed values).
	 **/
	return (((gint64) tp.tv_sec) + p->offset_sec) * NM_UTILS_NS_PER_SECOND +
	       tp.tv_nsec;
}

/**
 * nm_utils_get_monotonic_timestamp_us:
 *
 * Returns: a monotonically increasing time stamp in microseconds,
 * starting at an unspecified offset. See clock_gettime(), %CLOCK_BOOTTIME.
 *
 * The returned value will start counting at an undefined point
 * in the past and will always be positive.
 *
 * All the nm_utils_get_monotonic_timestamp_*s functions return the same
 * timestamp but in different scales (nsec, usec, msec, sec).
 **/
gint64
nm_utils_get_monotonic_timestamp_us (void)
{
	const GlobalState *p;
	struct timespec tp;

	p = _t_clock_gettime (&tp);

	/* Although the result will always be positive, we return a signed
	 * integer, which makes it easier to calculate time differences (when
	 * you want to subtract signed values).
	 **/
	return (((gint64) tp.tv_sec) + p->offset_sec) * ((gint64) G_USEC_PER_SEC) +
	       (tp.tv_nsec / (NM_UTILS_NS_PER_SECOND/G_USEC_PER_SEC));
}

/**
 * nm_utils_get_monotonic_timestamp_ms:
 *
 * Returns: a monotonically increasing time stamp in milliseconds,
 * starting at an unspecified offset. See clock_gettime(), %CLOCK_BOOTTIME.
 *
 * The returned value will start counting at an undefined point
 * in the past and will always be positive.
 *
 * All the nm_utils_get_monotonic_timestamp_*s functions return the same
 * timestamp but in different scales (nsec, usec, msec, sec).
 **/
gint64
nm_utils_get_monotonic_timestamp_ms (void)
{
	const GlobalState *p;
	struct timespec tp;

	p = _t_clock_gettime (&tp);

	/* Although the result will always be positive, we return a signed
	 * integer, which makes it easier to calculate time differences (when
	 * you want to subtract signed values).
	 **/
	return (((gint64) tp.tv_sec) + p->offset_sec) * ((gint64) 1000) +
	       (tp.tv_nsec / (NM_UTILS_NS_PER_SECOND/1000));
}

/**
 * nm_utils_get_monotonic_timestamp_s:
 *
 * Returns: nm_utils_get_monotonic_timestamp_ms() in seconds (throwing
 * away sub second parts). The returned value will always be positive.
 *
 * This value wraps after roughly 68 years which should be fine for any
 * practical purpose.
 *
 * All the nm_utils_get_monotonic_timestamp_*s functions return the same
 * timestamp but in different scales (nsec, usec, msec, sec).
 **/
gint32
nm_utils_get_monotonic_timestamp_s (void)
{
	const GlobalState *p;
	struct timespec tp;

	p = _t_clock_gettime (&tp);

	return (((gint64) tp.tv_sec) + p->offset_sec);
}

/**
 * nm_utils_monotonic_timestamp_as_boottime:
 * @timestamp: the monotonic-timestamp that should be converted into CLOCK_BOOTTIME.
 * @timestamp_ns_per_tick: How many nanoseconds make one unit of @timestamp? E.g. if
 *   @timestamp is in unit seconds, pass %NM_UTILS_NS_PER_SECOND; if @timestamp is
 *   in nanoseconds, pass 1; if @timestamp is in milliseconds, pass %NM_UTILS_NS_PER_SECOND/1000.
 *   This must be a multiple of 10, and between 1 and %NM_UTILS_NS_PER_SECOND.
 *
 * Returns: the monotonic-timestamp as CLOCK_BOOTTIME, as returned by clock_gettime().
 *   The unit is the same as the passed in @timestamp based on @timestamp_ns_per_tick.
 *   E.g. if you passed @timestamp in as seconds, it will return boottime in seconds.
 *
 *   Note that valid monotonic-timestamps are always positive numbers (counting roughly since
 *   the application is running). However, it might make sense to calculate a timestamp from
 *   before the application was running, hence negative @timestamp is allowed. The result
 *   in that case might also be a negative timestamp (in CLOCK_BOOTTIME), which would indicate
 *   that the timestamp lies in the past before the machine was booted.
 *
 * On older kernels that don't support CLOCK_BOOTTIME, the returned time is instead CLOCK_MONOTONIC.
 **/
gint64
nm_utils_monotonic_timestamp_as_boottime (gint64 timestamp, gint64 timestamp_ns_per_tick)
{
	const GlobalState *p;
	gint64 offset;

	/* only support ns-per-tick being a multiple of 10. */
	g_return_val_if_fail (timestamp_ns_per_tick == 1
	                      || (timestamp_ns_per_tick > 0 &&
	                          timestamp_ns_per_tick <= NM_UTILS_NS_PER_SECOND &&
	                          timestamp_ns_per_tick % 10 == 0),
	                      -1);

	/* if the caller didn't yet ever fetch a monotonic-timestamp, he cannot pass any meaningful
	 * value (because he has no idea what these timestamps would be). That would be a bug. */
	nm_assert (g_atomic_pointer_get (&p_global_state));

	p = _t_get_global_state ();

	nm_assert (p->offset_sec <= 0);

	/* calculate the offset of monotonic-timestamp to boottime. offset_s is <= 1. */
	offset = p->offset_sec * (NM_UTILS_NS_PER_SECOND / timestamp_ns_per_tick);

	nm_assert (offset <= 0 && offset > G_MININT64);

	/* check for overflow (note that offset is non-positive). */
	g_return_val_if_fail (timestamp < G_MAXINT64 + offset, G_MAXINT64);

	return timestamp - offset;
}

/**
 * nm_utils_monotonic_timestamp_from_boottime:
 * @boottime: the timestamp from CLOCK_BOOTTIME (or CLOCK_MONOTONIC, if
 *   kernel does not support CLOCK_BOOTTIME and monotonic timestamps are based
 *   on CLOCK_MONOTONIC).
 * @timestamp_ns_per_tick: the scale in which @boottime is. If @boottime is in
 *   nano seconds, this should be 1. If it is in milli seconds, this should be
 *   %NM_UTILS_NS_PER_SECOND/1000, etc.
 *
 * Returns: the same timestamp in monotonic timestamp scale.
 *
 * Note that commonly monotonic timestamps are positive. But they may not
 * be positive in this case. That's when boottime is taken from a time before
 * the monotonic timestamps started counting. So, that means a zero or negative
 * value is still a valid timestamp.
 *
 * This is the inverse of nm_utils_monotonic_timestamp_as_boottime().
 */
gint64
nm_utils_monotonic_timestamp_from_boottime (guint64 boottime, gint64 timestamp_ns_per_tick)
{
	const GlobalState *p;
	gint64 offset;

	/* only support ns-per-tick being a multiple of 10. */
	g_return_val_if_fail (timestamp_ns_per_tick == 1
	                      || (timestamp_ns_per_tick > 0 &&
	                          timestamp_ns_per_tick <= NM_UTILS_NS_PER_SECOND &&
	                          timestamp_ns_per_tick % 10 == 0),
	                      -1);

	p = _t_get_global_state ();

	nm_assert (p->offset_sec <= 0);

	/* calculate the offset of monotonic-timestamp to boottime. offset_s is <= 1. */
	offset = p->offset_sec * (NM_UTILS_NS_PER_SECOND / timestamp_ns_per_tick);

	nm_assert (offset <= 0 && offset > G_MININT64);

	/* check for overflow (note that offset is non-positive). */
	g_return_val_if_fail (boottime < G_MAXINT64, G_MAXINT64);

	return (gint64) boottime + offset;
}

gint64
nm_utils_clock_gettime_ns (clockid_t clockid)
{
	struct timespec tp;

	if (clock_gettime (clockid, &tp) != 0)
		return -NM_ERRNO_NATIVE (errno);
	return nm_utils_timespec_to_ns (&tp);
}

gint64
nm_utils_clock_gettime_ms (clockid_t clockid)
{
	struct timespec tp;

	if (clock_gettime (clockid, &tp) != 0)
		return -NM_ERRNO_NATIVE (errno);
	return nm_utils_timespec_to_ms (&tp);
}
