What he says :)

> On 05.05.2020, at 03:17, Levente Uzonyi <leves at caesar.elte.hu> wrote:
> 
> Hi Chris,
> 
> On Mon, 4 May 2020, Chris Muller wrote:
> 
>> Hi Levente,
>> This trades the "posix" nomenclature in the API for #microsecondClockValue.  "Posix" is a private matter to Chronology's implementation that should not be exposed in the API.
> 
> "Posix" has been there since 2016: Time class >> posixMicrosecondClockWithOffset:.
> Everyone gets an idea what kind of timestamp a method with posix in its name will return.
> The same does not apply to #microsecondClockValue, does it?
> 
> In my opinion exposing "Posix" has benefits.
> So, -1 to these changes. Details below.
> 
>>  - Chris
>> On Mon, May 4, 2020 at 6:42 PM <commits at source.squeak.org> wrote:
>>      Chris Muller uploaded a new version of Chronology-Core to project The Inbox:
>>      http://source.squeak.org/inbox/Chronology-Core-cmm.56.mcz
>> 
>>      ==================== Summary ====================
>> 
>>      Name: Chronology-Core-cmm.56
>>      Author: cmm
>>      Time: 4 May 2020, 6:42:27.516151 pm
>>      UUID: 3c97bedc-c192-4872-b0f2-e93199f506ce
>>      Ancestors: Chronology-Core-ul.54
>> 
>>      Building on Chronology-Core-ul.54:
>> 
>>      - Let #microsecondClockValue complement #millisecondClockValue, to offer higher precision.
>>      - New constructor, DateAndTime class>>#utcMicroseconds:, complements the above.
>>      - Make Time class>>#utcMicrosecondClock private to help avoid accidental improper use with the above.
>> 
>>      =============== Diff against Chronology-Core-ul.54 ===============
>> 
>>      Item was added:
>>      + ----- Method: DateAndTime class>>microsecondClockValue (in category 'smalltalk-80') -----
>>      + microsecondClockValue
>>      +       ^ self clock microsecondClockValue!
> 
> Why do we need this here? Especially in that category. This is clearly not part of any smalltalk-80 protocol.
> DateAndTime class >> ##millisecondClockValue has no senders, so we should remove that method instead of adding another unused one.
> 
>> 
>>      Item was added:
>>      + ----- Method: DateAndTime class>>utcMicroseconds: (in category 'instance creation') -----
>>      + utcMicroseconds: microsecondClockValue
>>      +       "Instantiate a DateAndTime in UTC from the value of my #microsecondClockValue."
>>      +       ^ super new
>>      +               utcMicroseconds: microsecondClockValue
>>      +               offset: 0!
>> 
>>      Item was changed:
>>        ----- Method: Time class>>estimateHighResClockTicksPerMillisecond (in category 'clock') -----
>>        estimateHighResClockTicksPerMillisecond
>> 
>>              | t0 t1 t2 t3 |
>> 
>>              "Count the ticks ellapsed during a 10ms busy loop"
>>      +       t0 := Time microsecondClockValue + 200.
>>      +       [Time microsecondClockValue >= t0] whileFalse.
>>      -       t0 := Time utcMicrosecondClock + 200.
>>      -       [Time utcMicrosecondClock >= t0] whileFalse.
>>              t1 := self highResClock.
>>      +       [Time microsecondClockValue >= (t0 + 10000)] whileFalse.
>>      +       t1 := self highResClock - t1 * 1000 // (Time microsecondClockValue - t0).
>>      -       [Time utcMicrosecondClock >= (t0 + 10000)] whileFalse.
>>      -       t1 := self highResClock - t1 * 1000 // (Time utcMicrosecondClock - t0).
> 
> The method uses the primitive directly to make the measurements as accurate as possible. This change would make them less accurate.
> 
>> 
>>              "Count the ticks ellapsed during a 20ms busy loop"
>>      +       t0 := Time microsecondClockValue + 200.
>>      +       [Time microsecondClockValue >= t0] whileFalse.
>>      -       t0 := Time utcMicrosecondClock + 200.
>>      -       [Time utcMicrosecondClock >= t0] whileFalse.
>>              t2 := self highResClock.
>>      +       [Time microsecondClockValue >= (t0 + 20000)] whileFalse.
>>      +       t2 := self highResClock - t2 * 1000 // (Time microsecondClockValue - t0).
>>      -       [Time utcMicrosecondClock >= (t0 + 20000)] whileFalse.
>>      -       t2 := self highResClock - t2 * 1000 // (Time utcMicrosecondClock - t0).
>> 
>>              "Count the ticks ellapsed during a 30ms busy loop"
>>      +       t0 := Time microsecondClockValue + 200.
>>      +       [Time microsecondClockValue >= t0] whileFalse.
>>      -       t0 := Time utcMicrosecondClock + 200.
>>      -       [Time utcMicrosecondClock >= t0] whileFalse.
>>              t3 := self highResClock.
>>      +       [Time microsecondClockValue >= (t0 + 30000)] whileFalse.
>>      +       t3 := self highResClock - t3 * 1000 // (Time microsecondClockValue - t0).
>>      -       [Time utcMicrosecondClock >= (t0 + 30000)] whileFalse.
>>      -       t3 := self highResClock - t3 * 1000 // (Time utcMicrosecondClock - t0).
>> 
>>              "Take the median of the 3 estimates as the best"
>>              ^ t1 <= t2
>>                      ifTrue: [t2 <= t3
>>                                      ifTrue: [t2]
>>                                      ifFalse: [t1 <= t3
>>                                                      ifTrue: [t3]
>>                                                      ifFalse: [t1]]]
>>                      ifFalse: [t1 <= t3
>>                                      ifTrue: [t1]
>>                                      ifFalse: [t2 <= t3
>>                                                      ifTrue: [t3]
>>                                                      ifFalse: [t2]]]!
>> 
>>      Item was added:
>>      + ----- Method: Time class>>microsecondClockValue (in category 'general inquiries') -----
>>      + microsecondClockValue
>>      +       "Answer the value of the microsecond clock, the number of microseconds elapsed since 1/1/1901 @ 00:00:00."
> 
> Wrong date there.
> 
>>      +       ^ self utcMicrosecondClock - MicrosecondsBetweenPosixEpochAndSqueakEpoch!
>> 
>>      Item was changed:
>>        ----- Method: Time class>>microsecondsToRun: (in category 'general inquiries') -----
>>        microsecondsToRun: timedBlock
>>              "Answer the number of microseconds timedBlock takes to return its value."
>> 
>>              | startUsecs |
>>              (self useHighResClockForTiming and: [self highResClock ~= 0])
>>                      ifTrue: [       ^(self nanosecondsToRunHighRes: timedBlock) + 500 // 1000].
>>      +       startUsecs := self microsecondClockValue.
>>      -       startUsecs := self utcMicrosecondClock.
>>              timedBlock value.
>>      +       ^self microsecondClockValue - startUsecs!
>>      -       ^self utcMicrosecondClock - startUsecs!
> 
> Again, decreases the measurement's accuracy.
> 
>> 
>>      Item was changed:
>>        ----- Method: Time class>>millisecondClockValue (in category 'general inquiries') -----
>>        millisecondClockValue
>>              "Answer the value of the millisecond clock."
>>      +       ^self microsecondClockValue // 1000!
>>      -
>>      -       ^self utcMicrosecondClock // 1000!
> 
> After loading, this change would break code relying on previous results of this method.
> 
>> 
>>      Item was changed:
>>        ----- Method: Time class>>nanosecondsToRun: (in category 'general inquiries') -----
>>        nanosecondsToRun: timedBlock
>>              "Answer the number of nanoseconds timedBlock takes to return its value.
>>              Use high resolution clock if available and preferred."
>> 
>>              | startUsecs |
>>              (self useHighResClockForTiming and: [self highResClock ~= 0])
>>                      ifTrue: [       ^(self nanosecondsToRunHighRes: timedBlock)].
>>              "Fallback to microseconds clock"
>>      +       startUsecs := self microsecondClockValue.
>>      -       startUsecs := self utcMicrosecondClock.
>>              timedBlock value.
>>      +       ^self microsecondClockValue - startUsecs * 1000!
>>      -       ^self utcMicrosecondClock - startUsecs * 1000!
> 
> Accuracy again.
> 
>> 
>>      Item was removed:
>>      - ----- Method: Time class>>posixUtcMicrosecondClock (in category 'clock') -----
>>      - posixUtcMicrosecondClock
>>      -       "Answer the UTC microseconds since the POSIX epoch (January 1st 1970 00:00:00 UTC)."
>>      -
>>      -       ^self utcMicrosecondClock - MicrosecondsBetweenPosixEpochAndSqueakEpoch!
>> 
>>      Item was changed:
>>      + ----- Method: Time class>>utcMicrosecondClock (in category 'private') -----
>>      - ----- Method: Time class>>utcMicrosecondClock (in category 'clock') -----
> 
> Does this mean that I have to reimplement the primitive in my external packages from now on?
> 
> 
> Levente
> 
>>        utcMicrosecondClock
>>              "Answer the UTC microseconds since the Smalltalk epoch (January 1st 1901, the start of the 20th century).
>>               The value is derived from the Posix epoch with a constant offset corresponding to elapsed microseconds
>>               between the two epochs according to RFC 868."
>>              <primitive: 240>
>>              ^0!
>