MutexLock

Acquires a mutex

Syntax

Declare Sub MutexLock ( ByVal id As Any Ptr )

Usage

MutexLock( id )

Parameters

id

The Any Ptr handle of the mutex to be locked.

Description

Mutexlock halts any other threads using a mutex "handle", generated by MutexCreate, until the handle is unlocked with MutexUnlock.

See MutexCreate for more general information on mutexes.

Example

'' 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. Declare Sub thread1( param As Any Ptr ) Declare Sub thread2( param As Any Ptr ) Declare Sub teletype (ByVal text As String, ByVal x As Integer, ByVal y As Integer) Dim Shared threadsync As Any Ptr Dim Shared thread1handle As Any Ptr Dim Shared thread2handle As Any Ptr '' Create a mutex to synchronize the threads threadsync = MutexCreate '' Call thread 1 thread1handle = ThreadCreate(@thread1) If thread1handle = 0 Then Print "Error creating thread1" End If '' Call thread 2 thread2handle = ThreadCreate(@thread2) If thread2handle = 0 Then Print "Error creating thread1" End If '' Wait until both threads are finished ThreadWait(thread1handle) ThreadWait(thread2handle) teletype "Testing.................", 1, 1 teletype "Testing again...........", 10, 1 '' Discard the mutex when we are through using teletype MutexDestroy threadsync Sleep End '' Thread 1 calls a simple "teletype" routine Sub thread1( param As Any Ptr ) teletype "This is a test...", 4, 1 End Sub '' ...As does thread 2 Sub thread2( param As Any Ptr ) teletype "This is another test...", 7, 1 End Sub '' Teletype unfurls some text across the screen at a given location Sub teletype (ByVal text As String, ByVal x As Integer, ByVal y As Integer) Dim i As Integer, a As Integer Dim text_length As Integer text_length = Len(text) For a = 0 To text_length '' MutexLock prevents the two simultaneously running '' threads from sharing "x", "y", and "a" MutexLock threadsync Locate x,(y+a) Print Chr(text[a]) '' MutexUnlock releases these variables for other use MutexUnlock threadsync Sleep 25 Next a End Sub

Dialect Differences

Threading is not allowed in the -lang qb dialect.

Platform Differences

The DOS version of FreeBASIC does not allow for threads, as the OS does not support them.
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