public static Schema DecodeSchema(ReadOnlyMemory <byte> buffer)
{
int bufferPosition = 0;
int schemaMessageLength = BinaryPrimitives.ReadInt32LittleEndian(buffer.Span.Slice(bufferPosition));
bufferPosition += sizeof(int);
if (schemaMessageLength == MessageSerializer.IpcContinuationToken)
{
// ARROW-6313, if the first 4 bytes are continuation message, read the next 4 for the length
if (buffer.Length <= bufferPosition + sizeof(int))
{
throw new InvalidDataException("Corrupted IPC message. Received a continuation token at the end of the message.");
}
schemaMessageLength = BinaryPrimitives.ReadInt32LittleEndian(buffer.Span.Slice(bufferPosition));
bufferPosition += sizeof(int);
}
ByteBuffer schemaBuffer = ArrowReaderImplementation.CreateByteBuffer(buffer.Slice(bufferPosition));
//DictionaryBatch not supported for now
DictionaryMemo dictionaryMemo = null;
var schema = MessageSerializer.GetSchema(ArrowReaderImplementation.ReadMessage <Flatbuf.Schema>(schemaBuffer), ref dictionaryMemo);
return(schema);
}
public async ValueTask <Schema> ReadSchema()
{
if (HasReadSchema)
{
return(Schema);
}
var moveNextResult = await _flightDataStream.MoveNext().ConfigureAwait(false);
if (!moveNextResult)
{
throw new Exception("No records or schema in this flight");
}
//AppMetadata will never be null, but length 0 if empty
//Those are skipped
if (_flightDataStream.Current.AppMetadata.Length > 0)
{
_applicationMetadatas.Add(_flightDataStream.Current.AppMetadata);
}
var header = _flightDataStream.Current.DataHeader.Memory;
Message message = Message.GetRootAsMessage(
ArrowReaderImplementation.CreateByteBuffer(header));
if (_flightDataStream.Current.FlightDescriptor != null)
{
_flightDescriptor = new FlightDescriptor(_flightDataStream.Current.FlightDescriptor);
}
switch (message.HeaderType)
{
case MessageHeader.Schema:
Schema = FlightMessageSerializer.DecodeSchema(message.ByteBuffer);
break;
default:
throw new Exception($"Expected schema as the first message, but got: {message.HeaderType.ToString()}");
}
return(Schema);
}