/// <summary>
/// Parses the binary image.
/// </summary>
/// <param name="buffer">Binary image to parse.</param>
/// <param name="startIndex">Start index into <paramref name="buffer"/> to begin parsing.</param>
/// <param name="length">Length of valid data within <paramref name="buffer"/>.</param>
/// <returns>The length of the data that was parsed.</returns>
/// <remarks>
/// This method is overridden to parse from cumulated frame images.
/// </remarks>
public override int ParseBinaryImage(byte[] buffer, int startIndex, int length)
{
// If frame image collector was used, make sure and parse from entire frame image...
if (m_frameHeader != null)
{
// If all configuration frame images have been received, we can safely start parsing
if (m_frameHeader.IsLastFrame)
{
FrameImageCollector frameImages = m_frameHeader.FrameImages;
if (frameImages != null)
{
// Each individual frame will already have had a CRC check, so we implement standard parse to
// bypass ChannelBase CRC frame validation on cumulative frame image
buffer = frameImages.BinaryImage;
length = frameImages.BinaryLength;
startIndex = 0;
// Parse out header, body and footer images
startIndex += ParseHeaderImage(buffer, startIndex, length);
startIndex += ParseBodyImage(buffer, startIndex, length - startIndex);
startIndex += ParseFooterImage(buffer, startIndex, length - startIndex);
// Include 2 bytes for CRC that was already validated
return(startIndex + 2);
}
}
// There are more configuration frame images coming, keep parser moving by returning total
// frame length that was already parsed.
return(State.ParsedBinaryLength);
}
return(base.ParseBinaryImage(buffer, startIndex, length));
}
// Static Methods
// Cumulates frame images
internal static void CumulateFrameImage(CommonFrameHeader parsedFrameHeader, byte[] buffer, int offset, ref FrameImageCollector frameImages)
{
// If this is the first frame, cumulate all partial frames together as one complete frame
if (parsedFrameHeader.IsFirstFrame)
{
frameImages = new FrameImageCollector();
}
try
{
// Append next frame image
frameImages.AppendFrameImage(buffer, offset, parsedFrameHeader.FrameLength);
}
catch
{
// Stop accumulation if CRC check fails
frameImages = null;
throw;
}
// Store a reference to frame image collection in common header state so configuration frame
// can be parsed from entire combined binary image collection when last frame is received
parsedFrameHeader.FrameImages = frameImages;
// Clear local reference to frame image collection if this is the last frame
if (parsedFrameHeader.IsLastFrame)
{
frameImages = null;
}
}