FileRegion.GetStream Metoda

Definice

Obor názvů:

System.IO.Log

Sestavení:

System.IO.Log.dll

Vrátí datový proud, který lze použít ke čtení dat, která se mají archivovat.

public:
 System::IO::Stream ^ GetStream();

public System.IO.Stream GetStream ();

member this.GetStream : unit -> System.IO.Stream

Public Function GetStream () As Stream

Návraty

Stream

Datový proud obsahující data, která se mají archivovat.

Výjimky

IOException

Požadavek nebylo možné provést kvůli neočekávané výjimce vstupně-výstupních operací.

NotSupportedException

Operace není podporovaná.

ObjectDisposedException

Metoda byla volána po odstranění sekvence.

OutOfMemoryException

Pro pokračování v provádění programu není dostatek paměti.

UnauthorizedAccessException

Operační systém odepře přístup k zadanému úložišti protokolů.

Příklady

Následující příklad ukazuje, jak archivovat úložiště protokolů do XML pomocí LogStore tříd a FileRegion .

class LogBackup
{
    static void ArchiveToXML(LogStore logStore, string fileName)
    {

        LogArchiveSnapshot snapshot = logStore.CreateLogArchiveSnapshot();
        {
            XmlTextWriter writer = new XmlTextWriter(fileName, System.Text.Encoding.ASCII);
            writer.WriteStartElement("logArchive");

            foreach (FileRegion region in snapshot.ArchiveRegions)
            {
                writer.WriteStartElement("fileRegion");
                writer.WriteElementString("path",
                                          region.Path);
                writer.WriteElementString("length",
                                        region.FileLength.ToString());
                writer.WriteElementString("offset",
                                          region.Offset.ToString());

                using (Stream dataStream = region.GetStream())
                {
                    byte[] data = new byte[dataStream.Length];
                    dataStream.Read(data, 0, data.Length);

                    writer.WriteElementString("data", System.Convert.ToBase64String(data));
                }

                writer.WriteEndElement();
            }

            writer.Close();
            logStore.SetArchiveTail(snapshot.LastSequenceNumber);
        }
    }

    static void RestoreFromXML(string fileName)
    {
        using (XmlTextReader reader = new XmlTextReader(fileName))
        {
            reader.ReadStartElement("logArchive");
            while (reader.IsStartElement())
            {
                string path;
                long length;
                long offset;
                path = reader.ReadElementString("path");
                length = System.Int64.Parse(reader.ReadElementString("length"));
                offset = System.Int64.Parse(reader.ReadElementString("offset"));
                string dataString = reader.ReadElementString("data");
                byte[] data = System.Convert.FromBase64String(dataString);
                FileStream fileStream;
                using (fileStream = new FileStream(path,
                                              FileMode.OpenOrCreate,
                                              FileAccess.Write))
                {
                    fileStream.SetLength(length);
                    fileStream.Position = offset;
                    fileStream.Write(data, 0, data.Length);
                }
            }
            reader.ReadEndElement();
        }
    }
}

Friend Class LogBackup
    Private Shared Sub ArchiveToXML(ByVal logStore As LogStore, ByVal fileName As String)


        Dim snapshot As LogArchiveSnapshot = logStore.CreateLogArchiveSnapshot()
            Dim writer As New XmlTextWriter(fileName, System.Text.Encoding.ASCII)
            writer.WriteStartElement("logArchive")

        For Each region As FileRegion In snapshot.ArchiveRegions
            With writer
                .WriteStartElement("fileRegion")
                .WriteElementString("path", region.Path)
                .WriteElementString("length", region.FileLength.ToString())
                .WriteElementString("offset", region.Offset.ToString())
            End With

            Using dataStream As Stream = region.GetStream()
                Dim data(dataStream.Length - 1) As Byte
                dataStream.Read(data, 0, data.Length)

                writer.WriteElementString("data", System.Convert.ToBase64String(data))
            End Using

            writer.WriteEndElement()
        Next region

            writer.Close()
            logStore.SetArchiveTail(snapshot.LastSequenceNumber)
    End Sub

    Private Shared Sub RestoreFromXML(ByVal fileName As String)
        Using reader As New XmlTextReader(fileName)
            reader.ReadStartElement("logArchive")
            Do While reader.IsStartElement()
                Dim path As String
                Dim length As Long
                Dim offset As Long
                path = reader.ReadElementString("path")
                length = System.Int64.Parse(reader.ReadElementString("length"))
                offset = System.Int64.Parse(reader.ReadElementString("offset"))
                Dim dataString = reader.ReadElementString("data")
                Dim data() = System.Convert.FromBase64String(dataString)
                Dim fileStream As FileStream
                fileStream = New FileStream(path, FileMode.OpenOrCreate, FileAccess.Write)
                Using fileStream
                    fileStream.SetLength(length)
                    fileStream.Position = offset
                    fileStream.Write(data, 0, data.Length)
                End Using
            Loop
            reader.ReadEndElement()
        End Using
    End Sub
End Class