Package io.github.mahmoudimus.quic.packet

Class PacketBuilder

java.lang.Object
io.github.mahmoudimus.quic.packet.PacketBuilder
public final class PacketBuilder extends Object
Builds a datagram of one or more coalesced packets: write a header, fill the frame space, then pad and protect. A client's Initial datagram must reach 1200 bytes (RFC 9000 section 14.1), which finish(int) pads to. 

 PacketBuilder b = new PacketBuilder(ByteBuffer.allocate(1500), 1500);
 ByteBuffer frames = b.begin(new PacketHeader.Initial(V1, dcid, scid, new byte[0], 0, 1), keys.local());
 Frame.Crypto.encode(frames, 0, clientHello, frames.remaining());
 b.finish(PacketBuilder.MIN_INITIAL_DATAGRAM);
 ByteBuffer datagram = b.datagram();

Instances are not thread-safe.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    MIN_INITIAL_DATAGRAM
    The smallest datagram that may carry a client's Initial packet (RFC 9000 section 14.1).

  • Constructor Summary

    Constructors
    Constructor
    Description
    PacketBuilder(ByteBuffer buffer, int maxDatagramSize)
    A builder that writes from the buffer's position.

  • Method Summary

    Modifier and Type
    Method
    Description
    ByteBuffer
    begin(PacketHeader.Numbered header, DirectionalKeys keys)
    Starts a packet after any already finished in this datagram.
    ByteBuffer
    datagram()
    The datagram built so far: every finished packet.
    int
    finish()
    Finishes the current packet without padding beyond what header protection needs.
    int
    finish(int minDatagramSize)
    Finishes the current packet: pads it so that header protection can sample it and, if minDatagramSize asks for it, so that the datagram reaches that size; then protects it.
    int
    remaining()
    The frame space left in the current packet.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • MIN_INITIAL_DATAGRAM

      public static final int MIN_INITIAL_DATAGRAM
      The smallest datagram that may carry a client's Initial packet (RFC 9000 section 14.1).
      See Also:

  • Constructor Details

    • PacketBuilder

      public PacketBuilder(ByteBuffer buffer, int maxDatagramSize)
      A builder that writes from the buffer's position.
      Parameters:
      buffer - the datagram buffer; packets are written from its position on
      maxDatagramSize - the largest datagram to build, such as the path MTU's UDP payload

  • Method Details

    • begin

      public ByteBuffer begin(PacketHeader.Numbered header, DirectionalKeys keys)
      Starts a packet after any already finished in this datagram.
      Parameters:
      header - the header, with the packet number to send
      keys - the sender's keys for the header's level
      Returns:
      the frame space: a buffer whose position is where frames go and whose limit leaves room for the AEAD tag; write frames at its position
      Throws:
      IllegalStateException - if a packet is already in progress
      BufferOverflowException - if the header does not fit; the builder is unchanged

    • remaining

      public int remaining()
      The frame space left in the current packet.
      Returns:
      the bytes that frames may still use

    • finish

      public int finish(int minDatagramSize)
      Finishes the current packet: pads it so that header protection can sample it and, if minDatagramSize asks for it, so that the datagram reaches that size; then protects it.
      Parameters:
      minDatagramSize - the size the datagram must reach with this packet, or 0
      Returns:
      the index just past the protected packet
      Throws:
      IllegalStateException - if no packet is in progress or the padding does not fit

    • finish

      public int finish()
      Finishes the current packet without padding beyond what header protection needs.
      Returns:
      the index just past the protected packet

    • datagram

      public ByteBuffer datagram()
      The datagram built so far: every finished packet.
      Returns:
      a view from the first packet to the end of the last finished one