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stream_frame.go
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stream_frame.go
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package wire
import (
"bytes"
"errors"
"io"
"v2ray.com/core/external/github.com/lucas-clemente/quic-go/internal/protocol"
"v2ray.com/core/external/github.com/lucas-clemente/quic-go/internal/qerr"
"v2ray.com/core/external/github.com/lucas-clemente/quic-go/internal/utils"
)
// A StreamFrame of QUIC
type StreamFrame struct {
StreamID protocol.StreamID
FinBit bool
DataLenPresent bool
Offset protocol.ByteCount
Data []byte
}
func parseStreamFrame(r *bytes.Reader, version protocol.VersionNumber) (*StreamFrame, error) {
typeByte, err := r.ReadByte()
if err != nil {
return nil, err
}
hasOffset := typeByte&0x4 > 0
frame := &StreamFrame{
FinBit: typeByte&0x1 > 0,
DataLenPresent: typeByte&0x2 > 0,
}
streamID, err := utils.ReadVarInt(r)
if err != nil {
return nil, err
}
frame.StreamID = protocol.StreamID(streamID)
if hasOffset {
offset, err := utils.ReadVarInt(r)
if err != nil {
return nil, err
}
frame.Offset = protocol.ByteCount(offset)
}
var dataLen uint64
if frame.DataLenPresent {
var err error
dataLen, err = utils.ReadVarInt(r)
if err != nil {
return nil, err
}
// shortcut to prevent the unnecessary allocation of dataLen bytes
// if the dataLen is larger than the remaining length of the packet
// reading the packet contents would result in EOF when attempting to READ
if dataLen > uint64(r.Len()) {
return nil, io.EOF
}
} else {
// The rest of the packet is data
dataLen = uint64(r.Len())
}
if dataLen != 0 {
frame.Data = make([]byte, dataLen)
if _, err := io.ReadFull(r, frame.Data); err != nil {
// this should never happen, since we already checked the dataLen earlier
return nil, err
}
}
if frame.Offset+frame.DataLen() > protocol.MaxByteCount {
return nil, qerr.Error(qerr.InvalidStreamData, "data overflows maximum offset")
}
return frame, nil
}
// Write writes a STREAM frame
func (f *StreamFrame) Write(b *bytes.Buffer, version protocol.VersionNumber) error {
if len(f.Data) == 0 && !f.FinBit {
return errors.New("StreamFrame: attempting to write empty frame without FIN")
}
typeByte := byte(0x8)
if f.FinBit {
typeByte ^= 0x1
}
hasOffset := f.Offset != 0
if f.DataLenPresent {
typeByte ^= 0x2
}
if hasOffset {
typeByte ^= 0x4
}
b.WriteByte(typeByte)
utils.WriteVarInt(b, uint64(f.StreamID))
if hasOffset {
utils.WriteVarInt(b, uint64(f.Offset))
}
if f.DataLenPresent {
utils.WriteVarInt(b, uint64(f.DataLen()))
}
b.Write(f.Data)
return nil
}
// Length returns the total length of the STREAM frame
func (f *StreamFrame) Length(version protocol.VersionNumber) protocol.ByteCount {
length := 1 + utils.VarIntLen(uint64(f.StreamID))
if f.Offset != 0 {
length += utils.VarIntLen(uint64(f.Offset))
}
if f.DataLenPresent {
length += utils.VarIntLen(uint64(f.DataLen()))
}
return length + f.DataLen()
}
// DataLen gives the length of data in bytes
func (f *StreamFrame) DataLen() protocol.ByteCount {
return protocol.ByteCount(len(f.Data))
}
// MaxDataLen returns the maximum data length
// If 0 is returned, writing will fail (a STREAM frame must contain at least 1 byte of data).
func (f *StreamFrame) MaxDataLen(maxSize protocol.ByteCount, version protocol.VersionNumber) protocol.ByteCount {
headerLen := 1 + utils.VarIntLen(uint64(f.StreamID))
if f.Offset != 0 {
headerLen += utils.VarIntLen(uint64(f.Offset))
}
if f.DataLenPresent {
// pretend that the data size will be 1 bytes
// if it turns out that varint encoding the length will consume 2 bytes, we need to adjust the data length afterwards
headerLen++
}
if headerLen > maxSize {
return 0
}
maxDataLen := maxSize - headerLen
if f.DataLenPresent && utils.VarIntLen(uint64(maxDataLen)) != 1 {
maxDataLen--
}
return maxDataLen
}
// MaybeSplitOffFrame splits a frame such that it is not bigger than n bytes.
// If n >= len(frame), nil is returned and nothing is modified.
func (f *StreamFrame) MaybeSplitOffFrame(maxSize protocol.ByteCount, version protocol.VersionNumber) (*StreamFrame, error) {
if maxSize >= f.Length(version) {
return nil, nil
}
n := f.MaxDataLen(maxSize, version)
if n == 0 {
return nil, errors.New("too small")
}
newFrame := &StreamFrame{
FinBit: false,
StreamID: f.StreamID,
Offset: f.Offset,
Data: f.Data[:n],
DataLenPresent: f.DataLenPresent,
}
f.Data = f.Data[n:]
f.Offset += n
return newFrame, nil
}