Blitzmax threading examples thread

Example: LockMutex, UnlockMutex, Creating multiple threads, Waiting for threads to end, Thread safe blitzmax function

This example will create a mass of threads that all print to the console. When the main thread decides its time to finish, it will wait for all the threads to finish by keeping a count of the number of threads that have finished.

Const total_background_threads:Int = 10

Global program_ending:Int = False
Global closed_threads:Int = 0

Local threads:Int[total_background_threads]

Local index:Int = 0
For index = 0 Until total_background_threads
	threads[index] = CreateThread(threadfunc,String(index))
Next

' - main thread runtime here
Graphics 640,480,0,60
Local count:Int = 0
Local value:Float = 0
Local size:Float = 0
Repeat
	Cls
	count:+1
	value = Abs(Cos(count))
	size = (value * 200) + 100
	SetColor((155.0*value)+100,100.0*value,100.0*value)
	DrawOval(MouseX()-(size/2),MouseY()-(size/2),size,size)
	SetColor(0,255,0)
	DrawText("Press esc to end",5,5)
	Flip
Until KeyDown(KEY_ESCAPE) = True
EndGraphics


' - terminate the background threads
'close all the thread handles
tprint  "*** closing threads"
program_ending = True
For index = 0 Until total_background_threads
	DetachThread(threads[index])
Next
'wait until all threads have closed
Repeat
	Delay 10
Until closed_threads = total_background_threads


' - thread functions
'background thread, this is the 2nd thread in the program
Function threadfunc:Object(nobject:Object)
	'pause for a bit before printing
	Local count:Int = 0
	Local timedelay:Int = Rand(200,2000)
	While program_ending = False
		Delay timedelay
		count:+1
		If program_ending = False tprint "background thread "+String(nobject)+" (call: "+count+")"
	Wend
	
	'increase closed thread count and display message
	closed_threads:+1
	tprint "closing background thread "+String(nobject)
End Function

'threaded print command, this will allow you to safely print within threads
Function tprint(ntext:String)
	'this will create a speciffic mutex for locking the print command to reuse every function call
	Global mutex:Int = CreateMutex()
	
	'lock the mutex
	'this function will ask the system "can i please lock the mutex", as the mutex can only have two states:
	' - locked
	' - unlocked
	'like a 'bit' (0 or 1), it means that only one thing can be in control of the mutex. The function will 
	'wait in line until the system says it can lock the mutex. It is important to no keep the mutex locked in a perminant
	'loop, especialy for a print command, as it is a regualrly used function.
	
	'if you try and lock the mutex, but it is already locked, it means another thread is currently printing something.
	'Once the print has completed and the mutex is unlocked, any calls to print during, will go through one by one until there
	'are no more attempts to locked the mutex and print.
	LockMutex(mutex)
	Print ntext
	
	'we have finished our printing so unlock the mutex so that other threads may use it
	UnlockMutex(mutex)
End Function