LogArchiveSnapshot Class

Definition

Namespace:

System.IO.Log

Assembly:

System.IO.Log.dll

Represents a snapshot of the LogStore instance that can be used to generate an archive.

C#

public sealed class LogArchiveSnapshot

Inheritance

Object

LogArchiveSnapshot

Examples

The following example shows how to use the LogArchiveSnapshot class to archive a LogStore to an XML document.

C#

class LogBackup
{
    static void ArchiveToXML(LogStore logStore, string fileName)
    {
        LogArchiveSnapshot snapshot = logStore.CreateLogArchiveSnapshot();

        XmlTextWriter writer = new XmlTextWriter(fileName, 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", Convert.ToBase64String(data));
            }
            writer.WriteEndElement();
        }
        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 = reader.ReadElementString("path");
                long length = Int64.Parse(reader.ReadElementString("length"));
                long offset = Int64.Parse(reader.ReadElementString("offset"));
                string dataString = reader.ReadElementString("data");
                byte[] data = 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();
        }
    }
}

Remarks

A LogArchiveSnapshot object contains the information necessary to generate a consistent backup of the data in a LogStore. The actual data is contained in the enumerable collection of FileRegion objects returned by the ArchiveRegions property. Each FileRegion instance represents a sequence of bytes in a file that must be archived.

The ArchiveTail, BaseSequenceNumber, and LastSequenceNumber properties are for informational purposes only. They can be recorded along with the archive data to provide optional information, but are not required to restore the data.

Properties

ArchiveRegions	Gets an enumerable collection of FileRegion instances containing the actual archival data.
ArchiveTail	Gets the sequence number of the LogStore archive tail at the time the snapshot was taken.
BaseSequenceNumber	Gets the base sequence number of the LogStore at the time the snapshot was taken.
LastSequenceNumber	Gets the last sequence number of the LogStore at the time the snapshot was taken.

Methods

Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)

Applies to