190 lines
4.7 KiB
Go
190 lines
4.7 KiB
Go
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package wire
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import (
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"bytes"
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"errors"
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"io"
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"github.com/lucas-clemente/quic-go/internal/protocol"
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"github.com/lucas-clemente/quic-go/quicvarint"
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)
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// A StreamFrame of QUIC
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type StreamFrame struct {
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StreamID protocol.StreamID
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Offset protocol.ByteCount
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Data []byte
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Fin bool
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DataLenPresent bool
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fromPool bool
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}
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func parseStreamFrame(r *bytes.Reader, _ protocol.VersionNumber) (*StreamFrame, error) {
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typeByte, err := r.ReadByte()
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if err != nil {
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return nil, err
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}
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hasOffset := typeByte&0x4 > 0
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fin := typeByte&0x1 > 0
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hasDataLen := typeByte&0x2 > 0
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streamID, err := quicvarint.Read(r)
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if err != nil {
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return nil, err
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}
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var offset uint64
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if hasOffset {
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offset, err = quicvarint.Read(r)
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if err != nil {
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return nil, err
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}
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}
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var dataLen uint64
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if hasDataLen {
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var err error
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dataLen, err = quicvarint.Read(r)
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if err != nil {
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return nil, err
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}
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} else {
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// The rest of the packet is data
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dataLen = uint64(r.Len())
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}
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var frame *StreamFrame
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if dataLen < protocol.MinStreamFrameBufferSize {
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frame = &StreamFrame{Data: make([]byte, dataLen)}
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} else {
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frame = GetStreamFrame()
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// The STREAM frame can't be larger than the StreamFrame we obtained from the buffer,
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// since those StreamFrames have a buffer length of the maximum packet size.
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if dataLen > uint64(cap(frame.Data)) {
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return nil, io.EOF
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}
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frame.Data = frame.Data[:dataLen]
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}
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frame.StreamID = protocol.StreamID(streamID)
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frame.Offset = protocol.ByteCount(offset)
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frame.Fin = fin
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frame.DataLenPresent = hasDataLen
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if dataLen != 0 {
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if _, err := io.ReadFull(r, frame.Data); err != nil {
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return nil, err
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}
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}
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if frame.Offset+frame.DataLen() > protocol.MaxByteCount {
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return nil, errors.New("stream data overflows maximum offset")
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}
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return frame, nil
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}
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// Write writes a STREAM frame
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func (f *StreamFrame) Write(b *bytes.Buffer, version protocol.VersionNumber) error {
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if len(f.Data) == 0 && !f.Fin {
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return errors.New("StreamFrame: attempting to write empty frame without FIN")
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}
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typeByte := byte(0x8)
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if f.Fin {
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typeByte ^= 0x1
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}
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hasOffset := f.Offset != 0
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if f.DataLenPresent {
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typeByte ^= 0x2
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}
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if hasOffset {
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typeByte ^= 0x4
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}
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b.WriteByte(typeByte)
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quicvarint.Write(b, uint64(f.StreamID))
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if hasOffset {
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quicvarint.Write(b, uint64(f.Offset))
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}
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if f.DataLenPresent {
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quicvarint.Write(b, uint64(f.DataLen()))
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}
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b.Write(f.Data)
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return nil
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}
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// Length returns the total length of the STREAM frame
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func (f *StreamFrame) Length(version protocol.VersionNumber) protocol.ByteCount {
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length := 1 + quicvarint.Len(uint64(f.StreamID))
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if f.Offset != 0 {
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length += quicvarint.Len(uint64(f.Offset))
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}
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if f.DataLenPresent {
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length += quicvarint.Len(uint64(f.DataLen()))
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}
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return length + f.DataLen()
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}
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// DataLen gives the length of data in bytes
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func (f *StreamFrame) DataLen() protocol.ByteCount {
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return protocol.ByteCount(len(f.Data))
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}
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// MaxDataLen returns the maximum data length
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// If 0 is returned, writing will fail (a STREAM frame must contain at least 1 byte of data).
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func (f *StreamFrame) MaxDataLen(maxSize protocol.ByteCount, version protocol.VersionNumber) protocol.ByteCount {
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headerLen := 1 + quicvarint.Len(uint64(f.StreamID))
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if f.Offset != 0 {
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headerLen += quicvarint.Len(uint64(f.Offset))
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}
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if f.DataLenPresent {
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// pretend that the data size will be 1 bytes
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// if it turns out that varint encoding the length will consume 2 bytes, we need to adjust the data length afterwards
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headerLen++
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}
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if headerLen > maxSize {
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return 0
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}
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maxDataLen := maxSize - headerLen
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if f.DataLenPresent && quicvarint.Len(uint64(maxDataLen)) != 1 {
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maxDataLen--
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}
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return maxDataLen
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}
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// MaybeSplitOffFrame splits a frame such that it is not bigger than n bytes.
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// It returns if the frame was actually split.
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// The frame might not be split if:
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// * the size is large enough to fit the whole frame
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// * the size is too small to fit even a 1-byte frame. In that case, the frame returned is nil.
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func (f *StreamFrame) MaybeSplitOffFrame(maxSize protocol.ByteCount, version protocol.VersionNumber) (*StreamFrame, bool /* was splitting required */) {
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if maxSize >= f.Length(version) {
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return nil, false
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}
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n := f.MaxDataLen(maxSize, version)
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if n == 0 {
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return nil, true
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}
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new := GetStreamFrame()
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new.StreamID = f.StreamID
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new.Offset = f.Offset
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new.Fin = false
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new.DataLenPresent = f.DataLenPresent
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// swap the data slices
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new.Data, f.Data = f.Data, new.Data
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new.fromPool, f.fromPool = f.fromPool, new.fromPool
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f.Data = f.Data[:protocol.ByteCount(len(new.Data))-n]
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copy(f.Data, new.Data[n:])
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new.Data = new.Data[:n]
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f.Offset += n
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return new, true
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}
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func (f *StreamFrame) PutBack() {
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putStreamFrame(f)
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}
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