Module: Hitimes::Initialize

Defined in:
lib/hitimes/initialize.rb

Overview

Internal: Internal setup that is done when the library is loaded

We want to determine what clock to use for this machine. So we need to intropect the ruby environment and then setup some initial constants. These methods are used in lib/hitimes/instant.rb to help setup the CLOCK_ID constant

Class Method Summary collapse

Class Method Details

.determine_clock_id ⇒ Object

Internal: Determine what clock to use for the machine we are one. We want the highest resolution clock possible, which should be nanosecond resolution.

Get the resolution of each clock id and then return the higest resolution id from the list

Returns the clock id to use on this ruby


53
54
55
56
57
58
59
60
61
62
 
# File 'lib/hitimes/initialize.rb', line 53

def determine_clock_id
  ids_and_resolutions = potential_clock_ids.map { |clock_id|
    [clock_id, Process.clock_getres(clock_id)]
  }

  # Sort them by the resolution - we want the smallest one first
  ids_and_resolutions.sort_by! { |pair| pair[1] }

  return ids_and_resolutions.first[0]
end

.potential_clock_ids ⇒ Object

Internal: Return the list of clock ids, in general priority order, assuming they all have the same resolution.

On OSX we probably want to use the MACH time first, and then fall back to CLOCK_… Constants on other machines.

The one requirement is that they are monotonically increasing clocks

Returns an array of clock ids


21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
 
# File 'lib/hitimes/initialize.rb', line 21

def potential_clock_ids
  Array.new.tap do |clock_ids|

    # if we're on OSX this will add in an additional clock_id, although not
    # sure why it is just a symbol and not a Process:: constant
    #
    begin
      Process.clock_getres(:MACH_ABSOLUTE_TIME_BASED_CLOCK_MONOTONIC)
      clock_ids << :MACH_ABSOLUTE_TIME_BASED_CLOCK_MONOTONIC
    rescue Errno::EINVAL
      # not on OSX
    end

    # General monotonic constants in general order of priority assuming they
    # all have the same resolution
    #
    %i[ CLOCK_MONOTONIC_RAW CLOCK_BOOTTIME CLOCK_MONOTONIC_PRECISE CLOCK_MONOTONIC ].each do |c|
      clock_ids << Process.const_get(c) if Process.const_defined?(c)
    end

  end
end