eventwaithandle.vb

清华大学出版社出版的 移动应用开发宝典 张大威（2008）的附书源代码

Imports System.Threading
Imports System.Runtime.InteropServices

Namespace System.Threading

    Public Enum EventResetMode
        AutoReset = 0
        ManualReset = 1
    End Enum

    Public Class EventWaitHandle
        Inherits WaitHandle

        Public Sub New(ByVal initialState As Boolean, ByVal mode As EventResetMode, ByVal name As String)
            Me.Handle = NativeMethods.CreateEvent(IntPtr.Zero, (mode = EventResetMode.ManualReset), initialState, name)
        End Sub

        Public Overrides Sub Close()
            If (Me.Handle <> WaitHandle.InvalidHandle) Then
                NativeMethods.CloseHandle(Me.Handle)
                Me.Handle = WaitHandle.InvalidHandle
            End If
        End Sub

        Public Function Reset() As Boolean
            Return NativeMethods.EventModify(Me.Handle, NativeMethods.EVENT.Reset)
        End Function

        Public Function [Set]() As Boolean
            Return NativeMethods.EventModify(Me.Handle, NativeMethods.EVENT.Set)
        End Function

        Public Shared Function WaitAny(ByVal waitHandles As WaitHandle()) As Integer
            Return EventWaitHandle.WaitAny(waitHandles, -1, False)
        End Function

        Public Shared Function WaitAny(ByVal waitHandles As WaitHandle(), ByVal millisecondsTimeout As Integer, ByVal exitContext As Boolean) As Integer
            Dim [handles] As IntPtr() = New IntPtr(waitHandles.Length - 1) {}
            Dim i As Integer = 0
            Do While (i < [handles].Length)
                [handles](i) = waitHandles(i).Handle
                i += 1
            Loop
            Return NativeMethods.WaitForMultipleObjects([handles].Length, [handles], False, millisecondsTimeout)
        End Function

        Public Overrides Function WaitOne() As Boolean
            Return Me.WaitOne(-1, False)
        End Function

        Public Overrides Function WaitOne(ByVal millisecondsTimeout As Integer, ByVal exitContext As Boolean) As Boolean
            Return (NativeMethods.WaitForSingleObject(Me.Handle, millisecondsTimeout) = 0)
        End Function

        Public Const WaitTimeout As Integer = &H102


        Friend Class NativeMethods

            <DllImport("coredll", SetLastError:=True)> _
            Friend Shared Function CloseHandle(ByVal hObject As IntPtr) As Boolean
            End Function

            <DllImport("coredll", SetLastError:=True)> _
            Friend Shared Function CreateEvent(ByVal lpEventAttributes As IntPtr, ByVal bManualReset As Boolean, ByVal bInitialState As Boolean, ByVal lpName As String) As IntPtr
            End Function

            <DllImport("coredll.dll", SetLastError:=True)> _
            Friend Shared Function EventModify(ByVal hEvent As IntPtr, ByVal ef As [EVENT]) As Boolean
            End Function

            <DllImport("coredll", SetLastError:=True)> _
            Friend Shared Function WaitForMultipleObjects(ByVal nCount As Integer, ByVal lpHandles As IntPtr(), ByVal fWaitAll As Boolean, ByVal dwMilliseconds As Integer) As Integer
            End Function

            <DllImport("coredll", SetLastError:=True)> _
            Friend Shared Function WaitForSingleObject(ByVal hHandle As IntPtr, ByVal dwMilliseconds As Integer) As Integer
            End Function

            Friend Enum [EVENT]
                PULSE = 1
                Reset = 2
                [Set] = 3
            End Enum

        End Class
    End Class

End Namespace