/*
 * Copyright © 2014 - 2015 Collabora, Ltd.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial
 * portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

/**
 * \file timespec.h
 *
 * Helpers to deal with timespec structures.
 */

#ifndef TIMESPEC_H
#define TIMESPEC_H

#include <stdint.h>
#include <assert.h>
#include <stdbool.h>

#include "c11/time.h"
#include "macros.h"

#define NSEC_PER_SEC 1000000000

/**
 * Add timespecs
 *
 * \param r[out] result: a + b
 * \param a[in] operand
 * \param b[in] operand
 */
static inline void
timespec_add(struct timespec *r,
             const struct timespec *a, const struct timespec *b)
{
   r->tv_sec = a->tv_sec + b->tv_sec;
   r->tv_nsec = a->tv_nsec + b->tv_nsec;
   if (r->tv_nsec > NSEC_PER_SEC) {
      r->tv_sec++;
      r->tv_nsec -= NSEC_PER_SEC;
   }
}

/**
 * Subtract timespecs
 *
 * \param r[out] result: a - b
 * \param a[in] operand
 * \param b[in] operand
 */
static inline void
timespec_sub(struct timespec *r,
             const struct timespec *a, const struct timespec *b)
{
   r->tv_sec = a->tv_sec - b->tv_sec;
   r->tv_nsec = a->tv_nsec - b->tv_nsec;
   if (r->tv_nsec < 0) {
      r->tv_sec--;
      r->tv_nsec += NSEC_PER_SEC;
   }
}

/**
 * Saturating timespec subtraction
 *
 * \param r[out] result: max(a - b, 0)
 * \param a[in] operand
 * \param b[in] operand
 */
static inline void
timespec_sub_saturate(struct timespec *r,
                      const struct timespec *a, const struct timespec *b)
{
   timespec_sub(r, a, b);
   if (r->tv_sec < 0) {
      r->tv_sec = 0;
      r->tv_nsec = 0;
   }
}

#define TIME_T_MAX \
   ((time_t)(((time_t)-1) > 0 ? u_uintN_max(sizeof(time_t) * 8) : \
                                u_intN_max(sizeof(time_t) * 8)))

/**
 * Add a nanosecond value to a timespec
 *
 * \param r[out] result: a + b
 * \param a[in] base operand as timespec
 * \param b[in] operand in nanoseconds
 * \return true if the calculation overflowed
 */
static inline bool
timespec_add_nsec(struct timespec *r, const struct timespec *a, uint64_t b)
{
   uint64_t b_sec = b / NSEC_PER_SEC;
   long b_nsec = b % NSEC_PER_SEC;
   bool overflow = (b_sec > (uint64_t)TIME_T_MAX) ||
                   ((uint64_t)a->tv_sec > (uint64_t)TIME_T_MAX - b_sec);

   r->tv_sec = (uint64_t)a->tv_sec + b_sec;
   r->tv_nsec = (uint64_t)a->tv_nsec + b_nsec;

   if (r->tv_nsec >= NSEC_PER_SEC) {
      if (r->tv_sec >= TIME_T_MAX)
         overflow = true;
      r->tv_sec = (uint64_t)r->tv_sec + 1ull;
      r->tv_nsec -= NSEC_PER_SEC;
   } else if (r->tv_nsec < 0) {
      assert(overflow);
      r->tv_sec--;
      r->tv_nsec += NSEC_PER_SEC;
   }

   return overflow;
}

/**
 * Add a millisecond value to a timespec
 *
 * \param r[out] result: a + b
 * \param a[in] base operand as timespec
 * \param b[in] operand in milliseconds
 * \return true if the calculation overflowed
 */
static inline bool
timespec_add_msec(struct timespec *r, const struct timespec *a, uint64_t b)
{
   return timespec_add_nsec(r, a, b * 1000000) || b > (UINT64_MAX / 1000000);
}

/**
 * Convert timespec to nanoseconds
 *
 * \param a timespec
 * \return nanoseconds
 */
static inline uint64_t
timespec_to_nsec(const struct timespec *a)
{
   return (uint64_t)a->tv_sec * NSEC_PER_SEC + a->tv_nsec;
}

/**
 * Subtract timespecs and return result in nanoseconds
 *
 * \param a[in] operand
 * \param b[in] operand
 * \return to_nanoseconds(a - b)
 */
static inline uint64_t
timespec_sub_to_nsec(const struct timespec *a, const struct timespec *b)
{
   struct timespec r;
   timespec_sub(&r, a, b);
   return timespec_to_nsec(&r);
}

/**
 * Convert timespec to milliseconds
 *
 * \param a timespec
 * \return milliseconds
 *
 * Rounding to integer milliseconds happens always down (floor()).
 */
static inline uint64_t
timespec_to_msec(const struct timespec *a)
{
   return (uint64_t)a->tv_sec * 1000 + a->tv_nsec / 1000000;
}

/**
 * Subtract timespecs and return result in milliseconds
 *
 * \param a[in] operand
 * \param b[in] operand
 * \return to_milliseconds(a - b)
 */
static inline uint64_t
timespec_sub_to_msec(const struct timespec *a, const struct timespec *b)
{
   return timespec_sub_to_nsec(a, b) / 1000000;
}

/**
 * Convert timespec to microseconds
 *
 * \param a timespec
 * \return microseconds
 *
 * Rounding to integer microseconds happens always down (floor()).
 */
static inline uint64_t
timespec_to_usec(const struct timespec *a)
{
   return (uint64_t)a->tv_sec * 1000000 + a->tv_nsec / 1000;
}

/**
 * Convert timespec to protocol data
 *
 * \param a timespec
 * \param tv_sec_hi[out] the high bytes of the seconds part
 * \param tv_sec_lo[out] the low bytes of the seconds part
 * \param tv_nsec[out] the nanoseconds part
 *
 * The input timespec must be normalized (the nanoseconds part should
 * be less than 1 second) and non-negative.
 */
static inline void
timespec_to_proto(const struct timespec *a, uint32_t *tv_sec_hi,
                  uint32_t *tv_sec_lo, uint32_t *tv_nsec)
{
   assert(a->tv_sec >= 0);
   assert(a->tv_nsec >= 0 && a->tv_nsec < NSEC_PER_SEC);

   uint64_t sec64 = a->tv_sec;

   *tv_sec_hi = sec64 >> 32;
   *tv_sec_lo = sec64 & 0xffffffff;
   *tv_nsec = a->tv_nsec;
}

/**
 * Convert nanoseconds to timespec
 *
 * \param a timespec
 * \param b nanoseconds
 */
static inline void
timespec_from_nsec(struct timespec *a, uint64_t b)
{
   a->tv_sec = b / NSEC_PER_SEC;
   a->tv_nsec = b % NSEC_PER_SEC;
}

/**
 * Convert microseconds to timespec
 *
 * \param a timespec
 * \param b microseconds
 */
static inline void
timespec_from_usec(struct timespec *a, uint64_t b)
{
   timespec_from_nsec(a, b * 1000);
}

/**
 * Convert milliseconds to timespec
 *
 * \param a timespec
 * \param b milliseconds
 */
static inline void
timespec_from_msec(struct timespec *a, uint64_t b)
{
   timespec_from_nsec(a, b * 1000000);
}

/**
 * Convert protocol data to timespec
 *
 * \param a[out] timespec
 * \param tv_sec_hi the high bytes of seconds part
 * \param tv_sec_lo the low bytes of seconds part
 * \param tv_nsec the nanoseconds part
 */
static inline void
timespec_from_proto(struct timespec *a, uint32_t tv_sec_hi,
                    uint32_t tv_sec_lo, uint32_t tv_nsec)
{
   a->tv_sec = ((uint64_t)tv_sec_hi << 32) + tv_sec_lo;
   a->tv_nsec = tv_nsec;
}

/**
 * Check if a timespec is zero
 *
 * \param a timespec
 * \return whether the timespec is zero
 */
static inline bool
timespec_is_zero(const struct timespec *a)
{
   return a->tv_sec == 0 && a->tv_nsec == 0;
}

/**
 * Check if two timespecs are equal
 *
 * \param a[in] timespec to check
 * \param b[in] timespec to check
 * \return whether timespecs a and b are equal
 */
static inline bool
timespec_eq(const struct timespec *a, const struct timespec *b)
{
   return a->tv_sec == b->tv_sec &&
      a->tv_nsec == b->tv_nsec;
}

/**
 * Convert milli-Hertz to nanoseconds
 *
 * \param mhz frequency in mHz, not zero
 * \return period in nanoseconds
 */
static inline uint64_t
millihz_to_nsec(uint32_t mhz)
{
   assert(mhz > 0);
   return 1000000000000LL / mhz;
}

/**
 * Checks whether a timespec value is after another
 *
 * \param a[in] timespec to compare
 * \param b[in] timespec to compare
 * \return whether a is after b
 */
static inline bool
timespec_after(const struct timespec *a, const struct timespec *b)
{
   return (a->tv_sec == b->tv_sec) ?
      (a->tv_nsec > b->tv_nsec) :
      (a->tv_sec > b->tv_sec);
}

#endif /* TIMESPEC_H */