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idiolatrie |
/******************************************************************************
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* ETHERLAB - FPGA To C# To LABVIEW Bridge *
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******************************************************************************
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* *
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* Copyright (C)2012 Mathias Hörtnagl *
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* *
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* This program is free software: you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation, either version 3 of the License, or *
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* (at your option) any later version. *
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* *
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* This program is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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* GNU General Public License for more details. *
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* *
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* You should have received a copy of the GNU General Public License *
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* along with this program. If not, see . *
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******************************************************************************/
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using PcapDotNet.Packets;
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namespace EtherLab
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{
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///
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/// Represents an EtherLab datagram.
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///
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/// An EtherLab Datagram sends data for all active channels in one
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/// packet whenever send() is called.
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/// A packet, whether sent or received, contains at most 8 independent
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/// data chunks of 16 bit size each.
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///
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///
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/// +-----+----------------+----------------+
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/// | Bit | 0-7 | 8-15 |
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/// +-----+----------------+----------------+
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/// | 0 | Version | Channels |
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/// +-----+----------------+----------------+
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/// | 16 | Channel A Data |
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/// +-----+---------------------------------+
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/// | 32 | Channel B Data |
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/// +-----+---------------------------------+
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/// : : :
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/// +-----+---------------------------------+
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/// | 112 | Channel H Data |
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/// +-----+---------------------------------+
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///
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///
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///
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/// Channel Field
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///
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/// The Channels field is 1 byte wide and can thus hold 8 seperate
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/// channels. An active channel is repesented by its flag set to 1.
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///
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/// +-----+-------------------------------+
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/// | Bit | 8-15 |
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/// +-----+---+---+---+---+---+---+---+---+
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/// | 8 | H | G | F | E | D | C | B | A |
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/// +-----+---+---+---+---+---+---+---+---+
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///
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/// Each channel is labeled with an alphabetic letter (A to H).
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///
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///
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public sealed class EtherLabDatagram : Datagram
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{
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private static class Offset
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{
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public const int Version = 0;
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public const int Channel = 1;
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public const int Data = 2;
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}
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///
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/// The number of bytes the EtherLab header takes.
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///
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public const int HeaderLength = 2;
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///
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/// The version number of the EtherLab protocol.
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///
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public byte Version
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{
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get { return this[Offset.Version]; }
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}
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///
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/// The channel number octet. Specifies the virtual channel this
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/// package belongs to.
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///
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public byte Channel
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{
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get { return this[Offset.Channel]; }
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}
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///
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/// The channel data. 8 channels, 16 bit wide each. Data segment is 40
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/// byte wide as we need at least 42 byte of payload for an Ethernet
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/// package (remaining 2 bytes are EtherLab header).
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///
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public byte[] Data
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{
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get
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{
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return ReadBytes(Offset.Data, Length - HeaderLength);
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}
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}
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///
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/// Constructor for a new EtherLab Datagram.
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///
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/// The buffer to write the layer to.
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/// The offset in the buffer to start writing the layer at.
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/// The datagram length.
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internal EtherLabDatagram(byte[] buffer, int offset, int length)
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: base(buffer, offset, length)
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{
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}
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///
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/// Creates a Layer that represents the datagram to be used with PacketBuilder.
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///
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public override ILayer ExtractLayer()
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{
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return new EtherLabLayer
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{
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Version = Version,
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Channel = Channel,
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Data = Data
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};
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}
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///
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/// Writes the Datagram to the buffer.
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///
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/// The buffer to write the layer to.
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/// The offset in the buffer to start writing the layer at.
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/// The EtherLab protocol version.
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/// The active channels.
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/// The channels' data.
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internal static void Write(byte[] buffer, int offset, byte version, byte channel, byte[] data)
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{
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buffer.Write(offset + Offset.Version, version);
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buffer.Write(offset + Offset.Channel, channel);
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for (int i = 0; i < 16; i++)
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buffer.Write(offset + Offset.Data + i, data[i]);
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}
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}
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}
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