Circular Buffer Demo
Imports System
Imports System.Threading
Public Class MainClass
Shared Sub Main()
' create shared object
Dim sharedLocation As New CHoldIntegerSynchronized()
sharedLocation.CreateStateOutput()
' Random object used by each thread
Dim randomObject As New Random()
' create CProducer and CConsumer objects
Dim producer As New CProducer(sharedLocation, randomObject)
Dim consumer As New CConsumer(sharedLocation, randomObject)
' create threads
Dim producerThread As New Thread(AddressOf producer.Produce)
Dim consumerThread As New Thread(AddressOf consumer.Consume)
' name threads
producerThread.Name = "Producer"
consumerThread.Name = "Consumer"
' start threads
producerThread.Start()
consumerThread.Start()
End Sub ' Main
End Class
Public Class CConsumer
Private sharedLocation As CHoldIntegerSynchronized
Private randomSleepTime As Random
' constructor
Public Sub New(ByVal sharedObject As CHoldIntegerSynchronized, _
ByVal randomObject As Random)
sharedLocation = sharedObject
randomSleepTime = randomObject
End Sub
Public Sub Consume()
Dim count, sum As Integer
For count = 1 To 10
Thread.Sleep(randomSleepTime.Next(1, 3000))
sum += sharedLocation.Buffer
Next
Console.WriteLine( "Total " & _
Thread.CurrentThread.Name & " consumed: " & sum & vbCrLf & _
Thread.CurrentThread.Name & " terminated." )
End Sub
End Class
Public Class CHoldIntegerSynchronized
Private mBuffer As Integer() = {-1, -1, -1}
Private occupiedBufferCount As Integer
Private readlocation, writeLocation As Integer
Public Sub New()
End Sub ' New
Property Buffer() As Integer
Get
SyncLock (Me)
If occupiedBufferCount = 0 Then
Console.WriteLine( "All buffers empty. " & _
Thread.CurrentThread.Name & " waits." )
Monitor.Wait(Me)
End If
Dim readValue As Integer = mBuffer(readlocation)
Console.WriteLine( Thread.CurrentThread.Name & " reads " & _
mBuffer(readlocation) )
occupiedBufferCount -= 1
readlocation = (readlocation + 1) Mod mBuffer.Length
CreateStateOutput()
Monitor.Pulse(Me)
Return readValue
End SyncLock
End Get
Set(ByVal Value As Integer)
SyncLock (Me)
If occupiedBufferCount = mBuffer.Length Then
Console.WriteLine( "All buffers full. " & _
Thread.CurrentThread.Name & " waits." )
Monitor.Wait(Me)
End If
mBuffer(writeLocation) = Value
Console.WriteLine( Thread.CurrentThread.Name & " writes " & _
mBuffer(writeLocation) )
occupiedBufferCount += 1
writeLocation = (writeLocation + 1) Mod _
mBuffer.Length
CreateStateOutput()
Monitor.Pulse(Me)
End SyncLock
End Set
End Property ' Buffer
Public Sub CreateStateOutput()
Dim i As Integer
Console.WriteLine( "(buffers occupied: " & _
occupiedBufferCount & ")" & vbCrLf & "buffers: " )
For i = 0 To mBuffer.GetUpperBound(0)
Console.Write( " " & mBuffer(i) & " " )
Next
For i = 0 To mBuffer.GetUpperBound(0)
Console.Write( "---- " )
Next
For i = 0 To mBuffer.GetUpperBound(0)
If (i = writeLocation AndAlso _
writeLocation = readlocation) Then
Console.Write( " WR " )
ElseIf i = writeLocation Then
Console.Write( " W " )
ElseIf i = readlocation Then
Console.Write( " R " )
Else
Console.Write( " " )
End If
Next
End Sub
End Class
Public Class CProducer
Private sharedLocation As CHoldIntegerSynchronized
Private randomSleepTime As Random
Public Sub New(ByVal sharedObject As CHoldIntegerSynchronized, _
ByVal randomObject As Random)
sharedLocation = sharedObject
randomSleepTime = randomObject
End Sub ' New
Public Sub Produce()
Dim count As Integer
For count = 11 To 20
Thread.Sleep(randomSleepTime.Next(1, 3000))
sharedLocation.Buffer = count
Next
Console.WriteLine( Thread.CurrentThread.Name & _
" done producing. " & vbCrLf & _
Thread.CurrentThread.Name & " terminated." )
End Sub
End Class
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