github.com/danielpfeifer02/quic-go-prio-packs@v0.41.0-28/internal/wire/datagram_frame.go (about)

     1  package wire
     2  
     3  import (
     4  	"bytes"
     5  	"io"
     6  
     7  	"github.com/danielpfeifer02/quic-go-prio-packs/internal/protocol"
     8  	"github.com/danielpfeifer02/quic-go-prio-packs/priority_setting"
     9  	"github.com/danielpfeifer02/quic-go-prio-packs/quicvarint"
    10  )
    11  
    12  // MaxDatagramSize is the maximum size of a DATAGRAM frame (RFC 9221).
    13  // By setting it to a large value, we allow all datagrams that fit into a QUIC packet.
    14  // The value is chosen such that it can still be encoded as a 2 byte varint.
    15  // This is a var and not a const so it can be set in tests.
    16  var MaxDatagramSize protocol.ByteCount = 16383
    17  
    18  // A DatagramFrame is a DATAGRAM frame
    19  type DatagramFrame struct {
    20  	DataLenPresent bool
    21  	Data           []byte
    22  
    23  	// DATAGRAM_PRIO_TAG
    24  	Priority priority_setting.Priority
    25  }
    26  
    27  func parseDatagramFrame(r *bytes.Reader, typ uint64, _ protocol.Version) (*DatagramFrame, error) {
    28  	f := &DatagramFrame{Priority: priority_setting.NoPriority}
    29  	f.DataLenPresent = typ&0x1 > 0
    30  
    31  	var length uint64
    32  	if f.DataLenPresent {
    33  		var err error
    34  		len, err := quicvarint.Read(r)
    35  		if err != nil {
    36  			return nil, err
    37  		}
    38  		if len > uint64(r.Len()) {
    39  			return nil, io.EOF
    40  		}
    41  		length = len
    42  	} else {
    43  		length = uint64(r.Len())
    44  	}
    45  	f.Data = make([]byte, length)
    46  	if _, err := io.ReadFull(r, f.Data); err != nil {
    47  		return nil, err
    48  	}
    49  	return f, nil
    50  }
    51  
    52  func (f *DatagramFrame) Append(b []byte, _ protocol.Version) ([]byte, error) {
    53  	typ := uint8(0x30)
    54  	if f.DataLenPresent {
    55  		typ ^= 0b1
    56  	}
    57  	b = append(b, typ)
    58  	if f.DataLenPresent {
    59  		b = quicvarint.Append(b, uint64(len(f.Data)))
    60  	}
    61  	b = append(b, f.Data...)
    62  	return b, nil
    63  }
    64  
    65  // MaxDataLen returns the maximum data length
    66  func (f *DatagramFrame) MaxDataLen(maxSize protocol.ByteCount, version protocol.Version) protocol.ByteCount {
    67  	headerLen := protocol.ByteCount(1)
    68  	if f.DataLenPresent {
    69  		// pretend that the data size will be 1 bytes
    70  		// if it turns out that varint encoding the length will consume 2 bytes, we need to adjust the data length afterwards
    71  		headerLen++
    72  	}
    73  	if headerLen > maxSize {
    74  		return 0
    75  	}
    76  	maxDataLen := maxSize - headerLen
    77  	if f.DataLenPresent && quicvarint.Len(uint64(maxDataLen)) != 1 {
    78  		maxDataLen--
    79  	}
    80  	return maxDataLen
    81  }
    82  
    83  // Length of a written frame
    84  func (f *DatagramFrame) Length(_ protocol.Version) protocol.ByteCount {
    85  	length := 1 + protocol.ByteCount(len(f.Data))
    86  	if f.DataLenPresent {
    87  		length += quicvarint.Len(uint64(len(f.Data)))
    88  	}
    89  	return length
    90  }