/// <summary>
/// Decodes the specified discovery metadata packet.
/// </summary>
/// <param name="packet">The packet to decode.</param>
public static DiscoveryMetadata Decode(byte[] packet)
{
// packet contains a length and a checksum at very least
if (packet.Length < sizeof(Int32) * 2)
{
return null;
}
// check content length
var contentLength = BitConverter.ToInt32(packet, 0);
if (packet.Length != contentLength + sizeof(Int32) * 2) // content + length + checksum
{
return null;
}
// validate checksum
var checksum = BitConverter.ToUInt32(packet, sizeof(Int32));
var crc = new Crc32Calculator();
crc.UpdateWithBlock(packet, sizeof(Int32) * 2, contentLength);
if (checksum != crc.Crc32)
{
return null;
}
// decode contents
var contents = packet.Skip(sizeof(Int32) * 2).ToArray();
var data = Encoding.UTF8.GetString(contents).Split(new[] { '|' }, StringSplitOptions.RemoveEmptyEntries);
if (data.Length < 1)
{
return null;
}
// extract signature and create the packet
var signature = Unescape(data.First());
var dp = CreateDiscoveryMetadata(signature);
if (dp == null)
{
return null;
}
// populate properties
foreach (var pair in data.Skip(1))
{
var entry = pair.Split('=');
dp.Properties[Unescape(entry.First())] = Unescape(entry.Last());
}
return dp;
}
/// <summary>
/// Encodes the specified discovery metadata packet into byte array.
/// </summary>
/// <param name="dp">The packet to encode.</param>
public static byte[] Encode(DiscoveryMetadata dp)
{
// convert the packet into string
var sb = new StringBuilder();
sb.AppendFormat("{0}|", Escape(dp.Signature));
foreach (var entry in dp.Properties)
{
sb.AppendFormat("{0}={1}|", Escape(entry.Key), Escape(entry.Value));
}
// calculate checksum and merge
var content = Encoding.UTF8.GetBytes(sb.ToString());
var crc = new Crc32Calculator();
crc.UpdateWithBlock(content, 0, content.Length);
var checksum = BitConverter.GetBytes(crc.Crc32);
var contentLength = BitConverter.GetBytes(content.Length);
// packet contents: length, checksum, content
return contentLength.Concat(checksum).Concat(content).ToArray();
}
