ThreadWait
Waits until the designated thread has been completed before returning
ThreadWait( id )
Threadwait doesn't return until the thread designated by id ends. Threadwait does not force the thread to end; if a thread requires a signal to force its end, a mechanism such as shared variables must be used.
Threads are launched by the ThreadCreate function.
To avoid simultaneous access to shared resources from different threads, FreeBASIC implements mutexes, mutual exclusion locks that can be "owned" by a single thread when doing critical work. See MutexCreate, MutexLock, MutexUnlock, MutexDestroy
Syntax
Usage
ThreadWait( id )
Parameters
Description
Threadwait doesn't return until the thread designated by id ends. Threadwait does not force the thread to end; if a thread requires a signal to force its end, a mechanism such as shared variables must be used.
Threads are launched by the ThreadCreate function.
To avoid simultaneous access to shared resources from different threads, FreeBASIC implements mutexes, mutual exclusion locks that can be "owned" by a single thread when doing critical work. See MutexCreate, MutexLock, MutexUnlock, MutexDestroy
Example
Dim Shared printsync As Any Ptr
Sub mythread(ByVal idp As Any Ptr)
Var id = CInt(idp)
Dim As Double t, w
Dim As Integer i, n
If( id = 1 ) Then
w = 1
n = 10
Else
w = 0.3
n = 5
End If
For i = 1 To n
MutexLock printsync
Print "Thread #"; id; ": on step #"; i
MutexUnlock printsync
'' simulate some work
t = Timer
While( Timer - t ) < w
Wend
Next i
MutexLock printsync
Print "Thread #"; id; " is done "
MutexUnlock printsync
End Sub
Dim As Any Ptr t1, t2
Print "Starting threads ... "
'' create a mutex to sync printing
printsync = MutexCreate()
'' create 2 threads, each taking a different
'' amount of time to complete
t1 = ThreadCreate( @mythread, Cast(Any Ptr, 1) )
t2 = ThreadCreate( @mythread, Cast(Any Ptr, 2) )
'' wait for threads to complete
ThreadWait( t1 )
ThreadWait( t2 )
MutexDestroy printsync
Print "All done."
Sub mythread(ByVal idp As Any Ptr)
Var id = CInt(idp)
Dim As Double t, w
Dim As Integer i, n
If( id = 1 ) Then
w = 1
n = 10
Else
w = 0.3
n = 5
End If
For i = 1 To n
MutexLock printsync
Print "Thread #"; id; ": on step #"; i
MutexUnlock printsync
'' simulate some work
t = Timer
While( Timer - t ) < w
Wend
Next i
MutexLock printsync
Print "Thread #"; id; " is done "
MutexUnlock printsync
End Sub
Dim As Any Ptr t1, t2
Print "Starting threads ... "
'' create a mutex to sync printing
printsync = MutexCreate()
'' create 2 threads, each taking a different
'' amount of time to complete
t1 = ThreadCreate( @mythread, Cast(Any Ptr, 1) )
t2 = ThreadCreate( @mythread, Cast(Any Ptr, 2) )
'' wait for threads to complete
ThreadWait( t1 )
ThreadWait( t2 )
MutexDestroy printsync
Print "All done."
Dialect Differences
- Threading is not allowed in -lang qb
Platform Differences
- Threadwait is not available with the DOS version / target of FreeBASIC, because multithreading is not supported by DOS kernel nor the used extender.
- In Linux the threads are always started in the order they are created, this can't be assumed in Win32. It's an OS, not a FreeBASIC issue.
Differences from QB
- New to Freebasic
See also
