/// <summary>
/// Changes the seek pointer to a new location relative to the beginning
///of the stream, the end of the stream, or the current seek pointer
/// </summary>
/// <param name="dlibMove">
/// The displacement to be added to the location indicated by the dwOrigin parameter.
/// If dwOrigin is STREAM_SEEK_SET, this is interpreted as an unsigned value rather than a signed value.
/// </param>
/// <param name="dwOrigin">
/// The origin for the displacement specified in dlibMove.
/// The origin can be the beginning of the file (STREAM_SEEK_SET), the current seek pointer (STREAM_SEEK_CUR), or the end of the file (STREAM_SEEK_END).
/// </param>
/// <param name="plibNewPosition">
/// The location where this method writes the value of the new seek pointer from the beginning of the stream.
/// It can be set to IntPtr.Zero. In this case, this method does not provide the new seek pointer.
/// </param>
/// <typeparam name="pcbRead">Native UInt64</typeparam>
/// <returns>
/// Returns in <paramref name="plibNewPosition"/> the location where this method writes the value of the new seek pointer from the beginning of the stream.
/// </returns>
///<exception cref="IOException">An I/O error occurs.</exception>
///<exception cref="NotSupportedException">The stream does not support reading.</exception>
///<exception cref="ObjectDisposedException">Methods were called after the stream was closed.</exception>
public void Seek(long dlibMove, int dwOrigin, IntPtr plibNewPosition)
{
if (TheStream != null)
{
// The enum values of SeekOrigin match the enum values of
// STREAM_SEEK, so we can just cast the dwOrigin to a SeekOrigin
if (plibNewPosition == IntPtr.Zero)
{
// User isn't interested in new position
TheStream.Seek(dlibMove, (SeekOrigin)dwOrigin);
}
else
{
var origin = (SeekOrigin)dwOrigin;
if (origin != SeekOrigin.Begin &&
origin != SeekOrigin.Current &&
origin != SeekOrigin.End)
{
origin = SeekOrigin.Begin;
}
Marshal.WriteInt64(plibNewPosition, TheStream.Seek(dlibMove, origin));
}
}
else
{
TheIStream.Seek(dlibMove, dwOrigin, plibNewPosition);
}
}
/// <summary>
/// Sets the position within the current stream.
/// </summary>
/// <param name="offset">A byte offset relative to the origin parameter.</param>
/// <param name="origin">A value of type SeekOrigin indicating the reference point used to obtain the new position.</param>
/// <returns>The new position within the current stream.</returns>
public override long Seek(long offset, System.IO.SeekOrigin origin)
{
if (TheIStream != null)
{
long position = 0;
var pos = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(long)));
Marshal.WriteInt64(pos, 0);
// The enum values of SeekOrigin match the enum values of
// STREAM_SEEK, so we can just cast the origin to an integer.
TheIStream.Seek(offset, (int)origin, pos);
position = Marshal.ReadInt64(pos);
Marshal.FreeHGlobal(pos);
return(position);
}
else
{
return(TheStream.Seek(offset, origin));
}
}