github.com/apernet/quic-go@v0.43.1-0.20240515053213-5e9e635fd9f0/internal/protocol/stream.go (about)

     1  package protocol
     2  
     3  // StreamType encodes if this is a unidirectional or bidirectional stream
     4  type StreamType uint8
     5  
     6  const (
     7  	// StreamTypeUni is a unidirectional stream
     8  	StreamTypeUni StreamType = iota
     9  	// StreamTypeBidi is a bidirectional stream
    10  	StreamTypeBidi
    11  )
    12  
    13  // InvalidPacketNumber is a stream ID that is invalid.
    14  // The first valid stream ID in QUIC is 0.
    15  const InvalidStreamID StreamID = -1
    16  
    17  // StreamNum is the stream number
    18  type StreamNum int64
    19  
    20  const (
    21  	// InvalidStreamNum is an invalid stream number.
    22  	InvalidStreamNum = -1
    23  	// MaxStreamCount is the maximum stream count value that can be sent in MAX_STREAMS frames
    24  	// and as the stream count in the transport parameters
    25  	MaxStreamCount StreamNum = 1 << 60
    26  )
    27  
    28  // StreamID calculates the stream ID.
    29  func (s StreamNum) StreamID(stype StreamType, pers Perspective) StreamID {
    30  	if s == 0 {
    31  		return InvalidStreamID
    32  	}
    33  	var first StreamID
    34  	switch stype {
    35  	case StreamTypeBidi:
    36  		switch pers {
    37  		case PerspectiveClient:
    38  			first = 0
    39  		case PerspectiveServer:
    40  			first = 1
    41  		}
    42  	case StreamTypeUni:
    43  		switch pers {
    44  		case PerspectiveClient:
    45  			first = 2
    46  		case PerspectiveServer:
    47  			first = 3
    48  		}
    49  	}
    50  	return first + 4*StreamID(s-1)
    51  }
    52  
    53  // A StreamID in QUIC
    54  type StreamID int64
    55  
    56  // InitiatedBy says if the stream was initiated by the client or by the server
    57  func (s StreamID) InitiatedBy() Perspective {
    58  	if s%2 == 0 {
    59  		return PerspectiveClient
    60  	}
    61  	return PerspectiveServer
    62  }
    63  
    64  // Type says if this is a unidirectional or bidirectional stream
    65  func (s StreamID) Type() StreamType {
    66  	if s%4 >= 2 {
    67  		return StreamTypeUni
    68  	}
    69  	return StreamTypeBidi
    70  }
    71  
    72  // StreamNum returns how many streams in total are below this
    73  // Example: for stream 9 it returns 3 (i.e. streams 1, 5 and 9)
    74  func (s StreamID) StreamNum() StreamNum {
    75  	return StreamNum(s/4) + 1
    76  }