libcURL.EasyHandle.DataAvailable

#libcURL.EasyHandle.DataAvailable

##Event Signature

 Event Function DataAvailable(NewData As MemoryBlock) As Integer

##Parameters

Name	Type	Comment
NewData	MemoryBlock	The data that is available.

##Return value The number of bytes successfully consumed which should be equal to the number of bytes provided. You may also return CURL_WRITEFUNC_PAUSE to consume no data and pause the download.

##Notes This event handles the CURLOPT_WRITEFUNCTION callback. It is raised by EasyHandle.WriteCallback. The new data is discarded once this event returns.

You must return the number of bytes that were successfully handled; if the number of bytes handled is different from the number of bytes provided then libcURL will assume that an error has occurred.

##A neat trick

On Linux and Mac OS X, you may optionally replace this callback with a file pointer which libcURL will automatically write downloaded data to. For example:

Function DownloadToFile(URL As String, ToFile As FolderItem) As Boolean
  #If TargetWin32 Then
    Return False
  #endif
  Dim curl As New libcURL.EasyHandle
  Dim filestream As BinaryStream = BinaryStream.Create(ToFile)
  Dim fstream As Integer = filestream.Handle(BinaryStream.HandleTypeFilePointer)
  Call curl.SetOption(libcURL.Opts.WRITEDATA, fstream)
  Call curl.SetOption(libcURL.Opts.WRITEFUNCTION, Nil)
  If Not curl.Perform(URL) Then MsgBox(libcURL.FormatError(curl.LastError))
  filestream.Close
  Return True
End Function

Attempting to do this under Win32 will cause libcURL to crash hard.

##See also

• EasyHandle._curlWrite
• EasyHandle.WriteCallback
• EasyHandle.cURLIOCallback