Module `Mtime`

Monotonic time values.

Mtime has platform independent support for monotonic wall-clock time. This time increases monotonically and is not subject to operating system calendar time adjustments.

Time spans represent non-negative monotonic time spans between two monotonic clock readings. Timestamps represent system-relative monotonic timestamps, their absolute value is meaningless but they can be compared across the processes of an operating system run.

Mtime_clock provides access to a system monotonic clock.

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Monotonic time spans

type span: The type for non-negative monotonic time spans. They represent the difference between two monotonic clock readings. If the platform's clock has nanosecond resolution the representation guarantees that the function Mtime_clock.elapsed can measure up to approximatively 584 Julian year spans before silently rolling over (unlikely since this is in a single program run).

module Span : sig ... end: Monotonic time spans.

Monotonic timestamps

Note. Only use timestamps if you need inter-process time correlation, otherwise prefer Mtime_clock.elapsed and counters.

type t: The type for monotonic timestamps relative to an indeterminate system-wide event (e.g. last startup). Their absolute value has no meaning but can be used for inter-process time correlation.

val to_uint64_ns : t -> int64: to_uint64_ns t is t as an unsigned 64-bit integer nanosecond timestamp. The absolute value is meaningless.

val of_uint64_ns : int64 -> t

to_uint64_ns t is t is an unsigned 64-bit integer nanosecond timestamp as a timestamp.

Warning. Timestamps returned by this function should only be used with other timestamp values that are know to come from the same operating system run.

Predicates

val equal : t -> t -> bool: equal t t' is true iff t and t' are equal.

val compare : t -> t -> int: compare t t' orders timestamps by increasing time.

val is_earlier : t -> than:t -> bool: is_earlier t ~than is true iff t occurred before than.

val is_later : t -> than:t -> bool: is_later t ~than is true iff t occurred after than.

Arithmetic

val span : t -> t -> span: span t t' is the span between t and t' regardless of the order between t and t'.

val add_span : t -> span -> t option: add_span t s is the timestamp s units later than t or None if the result overflows.

val sub_span : t -> span -> t option: sub_span t s is the timestamp s units earlier than t or None if overflows.

Pretty printing

val pp : Stdlib.Format.formatter -> t -> unit: pp ppf t prints t as an unsigned 64-bit integer nanosecond timestamp. Note that the absolute value is meaningless.

val dump : Stdlib.Format.formatter -> t -> unit: dump ppf t prints an unspecified raw representation of t on ppf.

Time scale conversion

The following convenience constants relate time scales to seconds. Used as multiplicands they can be used to convert these units to and from seconds.

The constants are defined according to SI prefixes on seconds and accepted non-SI units. Years are counted in Julian years (365.25 SI-accepted days) as defined by the International Astronomical Union (IAU).

val ns_to_s : float: ns_to_s is 1e-9 the number of seconds in one nanosecond.

val us_to_s : float: us_to_s is 1e-6, the number of seconds in one microsecond.

val ms_to_s : float: ms_to_s is 1e-3, the number of seconds in one millisecond.

val min_to_s : float: min_to_s is 60., the number of seconds in one SI-accepted minute.

val hour_to_s : float: hour_to_s is 3600., the number of seconds in one SI-accepted hour.

val day_to_s : float: day_to_s is 86_400., the number of seconds in one SI-accepted day.

val year_to_s : float: year_to_s is 31_557_600., the number of seconds in a Julian year.

val s_to_ns : float: s_to_ns is 1e9 the number of nanoseconds in one second.

val s_to_us : float: s_to_us is 1e6, the number of microseconds in one second.

val s_to_ms : float: s_to_ms is 1e3, the number of milliseconds in one second.

val s_to_min : float: s_to_min is 1. /. 60., the number of SI-accepted minutes in one second.

val s_to_hour : float: s_to_hour is 1. /. 3600., the number of SI-accepted hours in one second.

val s_to_day : float: s_to_day is 1. /. 86400., the number of SI-accepted days in one second.

val s_to_year : float: s_to_year is 1. /. 31_557_600., the number of Julian years in one second.