我正在使用FileSystemWatcher,当文件到达我的系统文件夹时通知我。
有时,它们到达时带有锁(由其他程序)
我想执行如下操作:
如果在TIMEOUT之后它们仍然被锁定,我们忽略该文件或者如果它们在TIMEOUT时间内无锁,我们处理文件
我目前想出了这个解决方案,但想知道是否有其他方法来实现它。
lockedFilePaths = new List<string>();
NoLockFilePaths = new List<string>();
Watcher.Created += (sender, e) => WatcherHandler(e.FullPath);
WatcherHandler(string FilePath)
{
CheckFileAccess(FilePath);
if (NoLockFilePaths.Any())
{
//Process all file paths
}
}
CheckFileAccess(string filepath)
{
// start a timer and invoke every say 10ms
// log the locked time of the file.
// compare the current time.
// return null if TIMEOUT exceeds
// or wait till the TIMEOUT and keep on checking the file access
}
问题是如何实现CheckFileAccess简单和最佳?
我目前使用System.Threading.Timer每1000毫秒通知我一次,检查文件是否仍然被锁定并且我的实现对我不满意。寻找一些超级简单的实现建议。
如果我必须做类似的事情,我会这样做:
public class Watcher
{
public readonly TimeSpan Timeout = TimeSpan.FromMinutes(10);
private readonly FileSystemWatcher m_SystemWatcher;
private readonly Queue<FileItem> m_Files;
private readonly Thread m_Thread;
private readonly object m_SyncObject = new object();
public Watcher()
{
m_Files = new Queue<FileItem>();
m_SystemWatcher = new FileSystemWatcher();
m_SystemWatcher.Created += (sender, e) => WatcherHandler(e.FullPath);
m_Thread = new Thread(ThreadProc)
{
IsBackground = true
};
m_Thread.Start();
}
private void WatcherHandler(string fullPath)
{
lock (m_SyncObject)
{
m_Files.Enqueue(new FileItem(fullPath));
}
}
private void ThreadProc()
{
while(true)//cancellation logic needed
{
FileItem item = null;
lock (m_SyncObject)
{
if (m_Files.Count > 0)
{
item = m_Files.Dequeue();
}
}
if (item != null)
{
CheckAccessAndProcess(item);
}
else
{
SpinWait.SpinUntil(() => m_Files.Count > 0, 200);
}
}
}
private void CheckAccessAndProcess(FileItem item)
{
if (CheckAccess(item))
{
Process(item);
}
else
{
if (DateTime.Now - item.FirstCheck < Timeout)
{
lock (m_SyncObject)
{
m_Files.Enqueue(item);
}
}
}
}
private bool CheckAccess(FileItem item)
{
if (IsFileLocked(item.Path))
{
if (item.FirstCheck == DateTime.MinValue)
{
item.SetFirstCheckDateTime(DateTime.Now);
}
return false;
}
return true;
}
private void Process(FileItem item)
{
//Do process stuff
}
private bool IsFileLocked(string file)
{
FileStream stream = null;
var fileInfo = new FileInfo(file);
try
{
stream = fileInfo.Open(FileMode.Open, FileAccess.ReadWrite, FileShare.None);
}
catch (IOException)
{
return true;
}
finally
{
if (stream != null)
stream.Close();
}
return false;
}
}
public class FileItem
{
public FileItem(string path)
{
Path = path;
FirstCheck = DateTime.MinValue;
}
public string Path { get; private set; }
public DateTime FirstCheck { get; private set; }
public void SetFirstCheckDateTime(DateTime now)
{
FirstCheck = now;
}
}
从CheckAccess和isfilellocked中,你可以返回FileStream对象,以确保在CheckAccess和process调用之间不会从另一个进程获得文件句柄;