/// <summary>
/// Update new row in data base and return the row identity
/// </summary>
/// <param name="id">Identity of row to be updated</param>
/// <param name="edge">Edge to be updated</param>
/// <returns>Success flag</returns>
private bool Update(long id, IPersistentEdge edge)
{
string edgeString = edge.Serialize();
edgeString = string.Concat(edgeString, Environment.NewLine);
byte[] buffer = ASCIIEncoding.ASCII.GetBytes(edgeString);
lock (lockObject)
{
_stream.Seek(id, SeekOrigin.Begin);
_stream.Write(buffer, 0, edgeString.Length);
_stream.Flush();
}
return(true);
}
/// <summary>
/// Insert a new row in data base and return the row identity
/// </summary>
/// <param name="edge">Edge to be inserted</param>
/// <returns>Id of new inserted row</returns>
private long Insert(IPersistentEdge edge)
{
// Append the new line character to each line
lock (lockObject)
{
_stream.Seek(0, SeekOrigin.End);
edge.Key = _stream.Position;
string edgeString = edge.Serialize();
edgeString = string.Concat(edgeString, Environment.NewLine);
byte[] buffer = ASCIIEncoding.ASCII.GetBytes(edgeString);
_stream.Write(buffer, 0, edgeString.Length);
_stream.Flush();
}
return(edge.Key);
}
/// <summary>
/// Write the edge to database storage.
/// 1. Serialize the given edge.
/// 2. Write it to the database.
/// 3. Return the Key(Id) of newly inserted row.
/// If the edge does not have key, insert a edge in storage
/// Else update the existing edge in storage
/// </summary>
/// <param name="edge">Edge to be stored</param>
/// <returns>Index / Key / Id / Offset of new edge</returns>
public long Write(IPersistentEdge edge)
{
if (edge == null)
{
throw new ArgumentNullException("edge");
}
if (edge.Key == -1)
{
edge.Key = Insert(edge);
}
else
{
Update(edge.Key, edge);
}
return(edge.Key);
}