用 C# 編寫網路電話 (5)：通知執行緒與播放邏輯核心實作

私有方法區域

#region 私有方法
private void InitNotifications()
{
    notifyThread = new Thread(NotifyThreadHandler);
    isRunning = true;
    notifyThread.IsBackground = true;
    notifyThread.Start();

    notificationEvent = new AutoResetEvent(false);
    notify = new Notify(m_Buffer);

    // 緩衝區切 4 段，每播放 1/4 發送訊號
    for (int i = 0; i < 4; i++)
    {
        positionNotify[i].Offset = ((notifySize * (i + 1)) - 1);
        positionNotify[i].EventNotifyHandle = notificationEvent.SafeWaitHandle.DangerousGetHandle();
    }
    notify.SetNotificationPositions(positionNotify, 4);
    nextWriteOffset = 0;
}

private void NotifyThreadHandler()
{
    while (isRunning)
    {
        try
        {
            notificationEvent.WaitOne(-1, true);
            Play();
        }
        catch (Exception) { }
    }
}

private void Play()
{
    try
    {
        int currentPlayPosition, currentWritePosition;
        m_Buffer.GetCurrentPosition(out currentPlayPosition, out currentWritePosition);

        int lockSize = currentWritePosition - nextWriteOffset;
        if (lockSize < 0) lockSize += m_BufferBytes; // 環狀回繞

        lockSize -= lockSize % notifySize; // 對齊通知粒度
        if (lockSize != 0)
        {
            byte[] data = new byte[lockSize];
            if (circularBuffer.Read(data) > 0)
            {
                m_Buffer.Write(nextWriteOffset, data, LockFlag.None);
                nextWriteOffset = (nextWriteOffset + lockSize) % m_BufferBytes;
            }
        }
    }
    catch (Exception) { }
    finally { }
}
#endregion

核心邏輯解析

1. 通知機制：AutoResetEvent + Notify 讓背景執行緒在播放位置到達特定點時喚醒。
2. 環狀寫入：計算可寫區塊大小、對齊、從 circularBuffer 讀取資料寫入 SecondaryBuffer，寫入指標模運算回繞。
3. Looping 播放：m_Buffer.Play(0, BufferPlayFlags.Looping) 使緩衝區循環播放，寫入指標歸零即無縫銜接。