' Threading synchronization 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_hilos = 10

Dim Shared As Any Ptr bloqueo_tty

' Teletipo unfurls some text across the screen at a given location
Sub Teletipo(Byref texto As String, Byval x As Integer, Byval 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 bloqueo_tty

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

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

Sub Hilo(Byval datos_usuario As Any Ptr)
    Dim As Integer id = Cint(datos_usuario)
    Teletipo "Hilo (" & id & ").........", 1 + id, 1
End Sub

' Create a mutex to syncronize the threads
bloqueo_tty = Mutexcreate()

' Create child threads
Dim As Any Ptr sucesos(0 To max_hilos - 1)
For i As Integer = 0 To max_hilos - 1
    sucesos(i) = Threadcreate(@Hilo, Cptr(Any Ptr, i))
    If sucesos(i) = 0 Then
        Print "Error al crear el hilo:"; i
        Exit For
    End If
Next i

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

' Clean up when finished
Mutexdestroy(bloqueo_tty)
Sleep