Package akka.stream.scaladsl

Class Framing

  • public class Framing
extends java.lang.Object

    • Constructor Detail

      • Framing

        public Framing()

    • Method Detail

      • delimiter

        public static Flow<ByteString,​ByteString,​NotUsed> delimiter​(ByteString delimiter,
                                                                        int maximumFrameLength,
                                                                        boolean allowTruncation)
        Creates a Flow that handles decoding a stream of unstructured byte chunks into a stream of frames where the incoming chunk stream uses a specific byte-sequence to mark frame boundaries.

        The decoded frames will not include the separator sequence.

        If there are buffered bytes (an incomplete frame) when the input stream finishes and ''allowTruncation'' is set to false then this Flow will fail the stream reporting a truncated frame.

        Parameters:
        delimiter - The byte sequence to be treated as the end of the frame.
        allowTruncation - If false, then when the last frame being decoded contains no valid delimiter this Flow fails the stream instead of returning a truncated frame.
        maximumFrameLength - The maximum length of allowed frames while decoding. If the maximum length is exceeded this Flow will fail the stream.

      • delimiter$default$3

        public static boolean delimiter$default$3()

      • lengthField

        public static Flow<ByteString,​ByteString,​NotUsed> lengthField​(int fieldLength,
                                                                          int fieldOffset,
                                                                          int maximumFrameLength,
                                                                          java.nio.ByteOrder byteOrder)
        Creates a Flow that decodes an incoming stream of unstructured byte chunks into a stream of frames, assuming that incoming frames have a field that encodes their length.

        If the input stream finishes before the last frame has been fully decoded, this Flow will fail the stream reporting a truncated frame.

        Parameters:
        fieldLength - The length of the "size" field in bytes
        fieldOffset - The offset of the field from the beginning of the frame in bytes
        maximumFrameLength - The maximum length of allowed frames while decoding. If the maximum length is exceeded this Flow will fail the stream. This length *includes* the header (i.e the offset and the length of the size field)
        byteOrder - The ''ByteOrder'' to be used when decoding the field

      • lengthField

        public static Flow<ByteString,​ByteString,​NotUsed> lengthField​(int fieldLength,
                                                                          int fieldOffset,
                                                                          int maximumFrameLength,
                                                                          java.nio.ByteOrder byteOrder,
                                                                          scala.Function2<byte[],​java.lang.Object,​java.lang.Object> computeFrameSize)
        Creates a Flow that decodes an incoming stream of unstructured byte chunks into a stream of frames, assuming that incoming frames have a field that encodes their length.

        If the input stream finishes before the last frame has been fully decoded, this Flow will fail the stream reporting a truncated frame.

        Parameters:
        fieldLength - The length of the "size" field in bytes
        fieldOffset - The offset of the field from the beginning of the frame in bytes
        maximumFrameLength - The maximum length of allowed frames while decoding. If the maximum length is exceeded this Flow will fail the stream. This length *includes* the header (i.e the offset and the length of the size field)
        byteOrder - The ''ByteOrder'' to be used when decoding the field
        computeFrameSize - This function can be supplied if frame size is varied or needs to be computed in a special fashion. For example, frame can have a shape like this: [offset bytes][body size bytes][body bytes][footer bytes]. Then computeFrameSize can be used to compute the frame size: (offset bytes, computed size) => (actual frame size). ''Actual frame size'' must be equal or bigger than sum of fieldOffset and fieldLength, the operator fails otherwise. Must not mutate the given byte array.

      • lengthField$default$2

        public static int lengthField$default$2()

      • lengthField$default$4

        public static java.nio.ByteOrder lengthField$default$4()

      • simpleFramingProtocol

        public static BidiFlow<ByteString,​ByteString,​ByteString,​ByteString,​NotUsed> simpleFramingProtocol​(int maximumMessageLength)
        Returns a BidiFlow that implements a simple framing protocol. This is a convenience wrapper over lengthField(int, int, int, java.nio.ByteOrder) and simply attaches a length field header of four bytes (using big endian encoding) to outgoing messages, and decodes such messages in the inbound direction. The decoded messages do not contain the header. 
        
       +--------------------------------+
       | Framing BidiFlow               |
       |                                |
       |  +--------------------------+  |
 in2 ~~>  |        Decoding          | ~~> out2
       |  +--------------------------+  |
       |                                |
       |  +--------------------------+  |
 out1 <~~ |Encoding(Add length field)| <~~ in1
       |  +--------------------------+  |
       +--------------------------------+
        This BidiFlow is useful if a simple message framing protocol is needed (for example when TCP is used to send individual messages) but no compatibility with existing protocols is necessary.

        The encoded frames have the layout 

        
   [4 bytes length field, Big Endian][User Payload]
        The length field encodes the length of the user payload excluding the header itself.

        Parameters:
        maximumMessageLength - Maximum length of allowed messages. If sent or received messages exceed the configured limit this BidiFlow will fail the stream. The header attached by this BidiFlow are not included in this limit.