'From Squeak4.2 of 3 May 2011 [latest update: #11376] on 3 May 2011 at 8:25:17 pm'!
Object subclass: #CheckTimeDrift
	instanceVariableNames: ''
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Junk'!
!CheckTimeDrift commentStamp: 'dtl 5/3/2011 20:13' prior: 0!
A CheckTimeDrift is a test for Squeak DateAndTime now versus the underlying platform time.

Prerequisites:
- Install TimeZoneDatabase from SqueakSource and set local time zone
- Run under an interpreter VM that provides #primitiveUtcWithOffset

Open a transcript, then doIt:

	[CheckTimeDrift run] fork inspect

!
]style[(221 22 34 25 10),c000000126,,c000126126,!


"-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- "!

CheckTimeDrift class
	instanceVariableNames: ''!

!CheckTimeDrift class methodsFor: 'running' stamp: 'dtl 5/3/2011 20:24'!
run
	"Load package TimeZoneDatabase. Set time zone. Run under an
	interpreter VM. Open transcript, then run."

	"[CheckTimeDrift run] fork"
	
	| start diff osTime squeakTime initialDifference drift |
	start := DateAndTime now.
	osTime := CheckTimeDrift now.
	squeakTime := DateAndTime now.
	initialDifference := squeakTime - osTime.

	[osTime := CheckTimeDrift now.
	squeakTime := DateAndTime now.
	diff := squeakTime - osTime.
	drift := diff - initialDifference.
	Transcript cr; nextPutAll: '=== Started at ', start printString, ' ==='.
	Transcript cr; nextPutAll: 'Test duration ', (squeakTime - start) printString.
	Transcript cr; nextPutAll: 'OS time now: ', osTime printString.
	Transcript cr; nextPutAll: 'Squeak time now: ', squeakTime printString.
	Transcript cr; nextPutAll: 'Difference: ', diff printString.
	Transcript cr; show: 'Drift: ', drift printString.
	(Delay forSeconds: 3) wait.
	] repeat! !


!CheckTimeDrift class methodsFor: 'time' stamp: 'dtl 5/3/2011 19:59'!
now

	"self now"

	| uSec pt |
	uSec := self primUtcWithOffset first.
	pt := PointInTime fromPosixSeconds: uSec / 1000000.
	^ pt asDateAndTime! !


!CheckTimeDrift class methodsFor: 'primitive access' stamp: 'dtl 5/3/2011 19:54'!
primUtcWithOffset
	"Answer an array with UTC microseconds since the Posix epoch and
	the current seconds offset from GMT in the local time zone.
	This is a named (not numbered) primitive in the null module (ie the VM)"
	
	"self primUtcWithOffset"
	
	<primitive: #primitiveUtcWithOffset>
	self error: 'use an interpreter VM, not Cog'! !