THREADCREATE - FreeBASIC Wiki Manual | FBWiki

'' Threading syncronyzation using Mutexes
'' If you comment out the lines containing "MutexLock" and "MutexUnlock",
'' the threads will not be in sync and some of the data may be printed
'' out of place.

Const MAX_THREADS = 10

Dim Shared As Any Ptr ttylock

'' Teletype unfurls some text across the screen at a given location
Sub teletype( text As String, x As Integer, y As Integer )
    ''
    '' This MutexLock makes simultaneously running threads wait for each
    '' other, so only one at a time can continue and print output.
    '' Otherwise, their Locates would interfere, since there is only one
    '' cursor.
    ''
    '' It's impossible to predict the order in which threads will arrive
    '' here and which one will be the first to acquire the lock thus
    '' causing the rest to wait.
    ''
    MutexLock ttylock

    For i As Integer = 0 To (Len(text) - 1)
        Locate x, y + i
        Print Chr(text[i])
        Sleep 25
    Next

    '' MutexUnlock releases the lock and lets other threads acquire it.
    MutexUnlock ttylock
End Sub

Sub thread( ByVal userdata As Any Ptr )
    Dim As Integer id = CInt(userdata)
    teletype "Thread (" & id & ").........", 1 + id, 1
End Sub

    '' Create a mutex to syncronize the threads
    ttylock = MutexCreate()

    '' Create child threads
    Dim As Any Ptr handles(0 To MAX_THREADS-1)
    For i As Integer = 0 To MAX_THREADS-1
        handles(i) = ThreadCreate(@thread, CPtr(Any Ptr, i))
        If handles(i) = 0 Then
            Print "Error creating thread:"; i
            Exit For
        End If
    Next

    '' This is the main thread. Now wait until all child threads have finished.
    For i As Integer = 0 To MAX_THREADS-1
        If handles(i) <> 0 Then
            ThreadWait(handles(i))
        End If
    Next

    '' Clean up when finished
    MutexDestroy(ttylock)

Sub print_dots(ByRef char As String)
    For i As Integer = 0 To 29
        Print char;
        Sleep CInt(Rnd() * 100), 1
    Next
End Sub

Sub mythread(param As Any Ptr)
    '' Work (other thread)
    print_dots("*")
End Sub

    Randomize(Timer())

    Print " main thread: ."
    Print "other thread: *"

    '' Launch another thread
    Dim As Any Ptr thread = ThreadCreate(@mythread, 0)

    '' Work (main thread)
    print_dots(".")

    '' Wait until other thread has finished, if needed
    ThreadWait(thread)
    Print
    Sleep

'' Threaded consumer/producer example using mutexes

Dim Shared As Any Ptr produced, consumed

Sub consumer( ByVal param As Any Ptr )
    For i As Integer = 0 To 9
        MutexLock produced
        Print ", consumer gets:", i
        Sleep 500
        MutexUnlock consumed
    Next
End Sub

Sub producer( ByVal param As Any Ptr )
    For i As Integer = 0 To 9
        Print "Producer puts:", i;
        Sleep 500
        MutexUnlock produced
        MutexLock consumed
    Next i
End Sub

    Dim As Any Ptr consumer_id, producer_id

    produced = MutexCreate
    consumed = MutexCreate
    If( ( produced = 0 ) Or ( consumed = 0 ) ) Then
        Print "Error creating mutexes! Exiting..."
        End 1
    End If

    MutexLock produced
    MutexLock consumed
    consumer_id = ThreadCreate(@consumer)
    producer_id = ThreadCreate(@producer)
    If( ( producer_id = 0 ) Or ( consumer_id = 0 ) ) Then
        Print "Error creating threads! Exiting..."
        End 1
    End If

    ThreadWait consumer_id
    ThreadWait producer_id

    MutexDestroy consumed
    MutexDestroy produced

    Sleep