public static EventStreamHeader FromBuffer(byte[] buffer, int offset, ref int newOffset)
{
newOffset = offset;
byte nameLength = buffer[newOffset++];
var header = new EventStreamHeader(Encoding.UTF8.GetString(buffer, newOffset, nameLength));
newOffset += nameLength;
header.HeaderType = (EventStreamHeaderType)buffer[newOffset++];
Int16 valueLength = 0;
switch (header.HeaderType)
{
case EventStreamHeaderType.BoolTrue:
header.HeaderValue = true;
break;
case EventStreamHeaderType.BoolFalse:
header.HeaderValue = false;
break;
case EventStreamHeaderType.Byte:
header.HeaderValue = buffer[newOffset];
newOffset += _sizeOfByte;
break;
case EventStreamHeaderType.Int16:
header.HeaderValue = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(buffer, newOffset));
newOffset += _sizeOfInt16;
break;
case EventStreamHeaderType.Int32:
header.HeaderValue = IPAddress.NetworkToHostOrder(BitConverter.ToInt32(buffer, newOffset));
newOffset += _sizeOfInt32;
break;
case EventStreamHeaderType.Int64:
header.HeaderValue = IPAddress.NetworkToHostOrder(BitConverter.ToInt64(buffer, newOffset));
newOffset += _sizeOfInt64;
break;
case EventStreamHeaderType.ByteBuf:
valueLength = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(buffer, newOffset));
newOffset += _sizeOfInt16;
header.HeaderValue = new byte[valueLength];
Buffer.BlockCopy(buffer, newOffset, header.HeaderValue as byte[], 0, valueLength);
newOffset += valueLength;
break;
case EventStreamHeaderType.String:
valueLength = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(buffer, newOffset));
newOffset += _sizeOfInt16;
header.HeaderValue = Encoding.UTF8.GetString(buffer, newOffset, valueLength);
newOffset += valueLength;
break;
case EventStreamHeaderType.Timestamp:
Int64 tempValue = IPAddress.NetworkToHostOrder(BitConverter.ToInt64(buffer, newOffset));
newOffset += _sizeOfInt64;
//keep in mind on the windows APIs (and hence NetStandard as well) the epoch is 1/1/1900,
//and we're using unix epoch. So we compensate here.
header.HeaderValue = _unixEpoch.AddMilliseconds(tempValue);
break;
case EventStreamHeaderType.UUID:
var guidCpy = new byte[16];
valueLength = _sizeOfGuid;
Buffer.BlockCopy(buffer, newOffset, guidCpy, 0, valueLength);
newOffset += valueLength;
header.HeaderValue = new Guid(guidCpy);
break;
default:
throw new EventStreamParseException(string.Format(CultureInfo.InvariantCulture, "Header Type: {0} is an unknown type.", header.HeaderType));
}
return(header);
}
/// <summary>
/// Builds a message from buffer.
/// </summary>
/// <param name="buffer">buffer to read</param>
/// <param name="offset">offset to start reading</param>
/// <param name="length">buffer length.</param>
/// <returns>
/// parsed instance of EventStreamMessage. Doesn't return null,
/// does throw if CRCs don't match.
/// </returns>
public static EventStreamMessage FromBuffer(byte[] buffer, int offset, int length)
{
var currentOffset = offset;
//get the total length of the message
var totalLength = BitConverter.ToInt32(buffer, currentOffset);
//endianness conversion
totalLength = EndianConversionUtility.NetworkToHostOrder(totalLength);
currentOffset += SizeOfInt32;
//get the length of the headers block.
var headersLength = BitConverter.ToInt32(buffer, currentOffset);
//endianness conversion
headersLength = EndianConversionUtility.NetworkToHostOrder(headersLength);
currentOffset += SizeOfInt32;
//get the prelude crc
var preludeCrc = BitConverter.ToInt32(buffer, currentOffset);
//endianness conversion
preludeCrc = EndianConversionUtility.NetworkToHostOrder(preludeCrc);
var message = new EventStreamMessage();
message.Headers = new Dictionary <string, IEventStreamHeader>(StringComparer.Ordinal);
using (var nullStream = new NullStream())
using (var runningChecksum = new CrcCalculatorStream(nullStream))
{
//write up to the prelude crc to the checksum stream
runningChecksum.Write(buffer, offset, currentOffset - offset);
//compare the current crc to the prelude crc and make sure they match.
if (preludeCrc != runningChecksum.Crc32)
{
throw new EventStreamChecksumFailureException(string.Format(CultureInfo.InvariantCulture, "Message Prelude Checksum failure. Expected {0} but was {1}", preludeCrc, runningChecksum.Crc32));
}
//if the data length passed isn't enough for the total length, that's an error condition.
if (totalLength != length)
{
throw new EventStreamChecksumFailureException(
string.Format(CultureInfo.InvariantCulture, "Message Total Length didn't match the passed in length. Expected {0} but was {1}", length, totalLength));
}
//now write the prelude crc to the checksum stream
runningChecksum.Write(buffer, currentOffset, SizeOfInt32);
currentOffset += SizeOfInt32;
//prelude length is total message, minus framing and headers size.
var payloadLength = totalLength - headersLength - FramingSize;
//if we have headers, then loop over each one and parse them out.
if (headersLength > 0)
{
int preOpOffset = currentOffset;
while (currentOffset - PreludeLen < headersLength)
{
EventStreamHeader header = EventStreamHeader.FromBuffer(buffer, currentOffset, ref currentOffset);
message.Headers.Add(header.Name, header);
}
//after parsing the header remember to write that data to the checksum stream
runningChecksum.Write(buffer, preOpOffset, currentOffset - preOpOffset);
}
// now we're on the payload
message.Payload = new byte[payloadLength];
Buffer.BlockCopy(buffer, currentOffset, message.Payload, 0, message.Payload.Length);
runningChecksum.Write(buffer, currentOffset, message.Payload.Length);
currentOffset += message.Payload.Length;
//after reading the payload, get the message crc and make sure it matches.
var trailingCrc = BitConverter.ToInt32(buffer, currentOffset);
//endianness conversion.
trailingCrc = EndianConversionUtility.NetworkToHostOrder(trailingCrc);
if (trailingCrc != runningChecksum.Crc32)
{
throw new EventStreamChecksumFailureException(
string.Format(CultureInfo.InvariantCulture, "Message Checksum failure. Expected {0} but was {1}", trailingCrc, runningChecksum.Crc32));
}
}
return(message);
}
