'From Croquet1.0beta of 11 April 2006 [latest update: #1] on 21 July 2008 at 2:21:25 pm'!
!MessageTally methodsFor: 'initialize-release' stamp: 'eem 7/21/2008 12:09'!
spyEvery: millisecs on: aBlock 
	"Create a spy and spy on the given block at the specified rate."

	| myDelay startTime time0 |
	aBlock isBlock
		ifTrue: [self class: aBlock receiver class method: aBlock method]
		ifFalse: [self class: aBlock class method: aBlock method].
		"set up the probe"
	ObservedProcess := Processor activeProcess.
	myDelay := Delay forMilliseconds: millisecs.
	time0 := Time millisecondClockValue.
	gcStats := SmalltalkImage current getVMParameters.
	Timer :=
		[[true] whileTrue: 
			[startTime := Time millisecondClockValue.
			myDelay wait.
			self tally: ObservedProcess suspendedContext
				"tally can be > 1 if ran a long primitive"
				by: (Time millisecondClockValue - startTime) // millisecs].
		nil] newProcess.
	Timer priority: Processor userInterruptPriority.
		"activate the probe and evaluate the block"
	Timer resume.
	^ aBlock ensure:
		["Collect gc statistics"
		SmalltalkImage current getVMParameters keysAndValuesDo:
			[:idx :gcVal| gcStats at: idx put: (gcVal - (gcStats at: idx))].
		"cancel the probe and return the value"
		Timer terminate.
		time := Time millisecondClockValue - time0]! !