ReadData Event

Fires when the cache needs to read file data from external storage.

Syntax

• C#
• VB.NET

public event OnReadDataHandler OnReadData;

public delegate void OnReadDataHandler(object sender, FilecacheReadDataEventArgs e);

public class FilecacheReadDataEventArgs : EventArgs {
  public string FileId { get; }
  public long Size { get; }
  public long Position { get; }
  public int Flags { get; }
  public byte[] Buffer { get; }
  public int BytesToRead { get; }
  public int BytesRead { get; set; }
  public long FileContext { get; }
  public int ResultCode { get; set; }
}

Public Event OnReadData As OnReadDataHandler

Public Delegate Sub OnReadDataHandler(sender As Object, e As FilecacheReadDataEventArgs)

Public Class FilecacheReadDataEventArgs Inherits EventArgs
  Public ReadOnly Property FileId As String
  Public ReadOnly Property Size As Long
  Public ReadOnly Property Position As Long
  Public ReadOnly Property Flags As Integer
  Public ReadOnly Property Buffer As Byte()
  Public ReadOnly Property BytesToRead As Integer
  Public Property BytesRead As Integer
  Public ReadOnly Property FileContext As Long
  Public Property ResultCode As Integer
End Class

Remarks

This event fires when the cache needs to read data for the cached file identified by FileId from external storage.

The Size parameter reflects the specified file's "real size", as it is currently known by the cache.

The Position parameter reflects the byte offset in the real file (i.e., the one in external storage) from which the application should start reading data.

The Flags parameter provides supplementary information about the nature of the request. This parameter, along with the Size and Position parameters, helps the application to determine which part of the file Buffer represents, and whether additional ReadData events should be expected. It will be a combination of one or more of the following flags:

To handle this event property, applications must read BytesToRead bytes of data from the real file in external storage, starting at the specified Position, into Buffer. When reading is complete, applications must set BytesRead to reflect the actual number of bytes read from the real file. Applications must not attempt to copy more than BytesToRead bytes of data into Buffer.

The FileContext parameter reflects the application-defined value passed when OpenFile was called.

The ResultCode parameter will always be 0 when the event is fired. If the event cannot be handled in a "successful" manner for some reason (e.g., a resource isn't available, security checks failed, etc.), set it to one of the following values to report an appropriate error:

Please refer to the Error Reporting and Handling topic for more information.