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package wire
import (
"errors"
"io"
"github.com/quic-go/quic-go/internal/protocol"
"github.com/quic-go/quic-go/quicvarint"
)
// A StreamFrame of QUIC
type StreamFrame struct {
StreamID protocol.StreamID
Offset protocol.ByteCount
Data []byte
Fin bool
DataLenPresent bool
fromPool bool
}
func ParseStreamFrame(b []byte, typ FrameType, _ protocol.Version) (*StreamFrame, int, error) {
startLen := len(b)
hasOffset := typ&0b100 > 0
fin := typ&0b1 > 0
hasDataLen := typ&0b10 > 0
streamID, l, err := quicvarint.Parse(b)
if err != nil {
return nil, 0, replaceUnexpectedEOF(err)
}
b = b[l:]
var offset uint64
if hasOffset {
offset, l, err = quicvarint.Parse(b)
if err != nil {
return nil, 0, replaceUnexpectedEOF(err)
}
b = b[l:]
}
var dataLen uint64
if hasDataLen {
var err error
var l int
dataLen, l, err = quicvarint.Parse(b)
if err != nil {
return nil, 0, replaceUnexpectedEOF(err)
}
b = b[l:]
if dataLen > uint64(len(b)) {
return nil, 0, io.EOF
}
} else {
// The rest of the packet is data
dataLen = uint64(len(b))
}
var frame *StreamFrame
if dataLen < protocol.MinStreamFrameBufferSize {
frame = &StreamFrame{}
if dataLen > 0 {
frame.Data = make([]byte, dataLen)
}
} else {
frame = GetStreamFrame()
// The STREAM frame can't be larger than the StreamFrame we obtained from the buffer,
// since those StreamFrames have a buffer length of the maximum packet size.
if dataLen > uint64(cap(frame.Data)) {
return nil, 0, io.EOF
}
frame.Data = frame.Data[:dataLen]
}
frame.StreamID = protocol.StreamID(streamID)
frame.Offset = protocol.ByteCount(offset)
frame.Fin = fin
frame.DataLenPresent = hasDataLen
if dataLen > 0 {
copy(frame.Data, b)
}
if frame.Offset+frame.DataLen() > protocol.MaxByteCount {
return nil, 0, errors.New("stream data overflows maximum offset")
}
return frame, startLen - len(b) + int(dataLen), nil
}
func (f *StreamFrame) Append(b []byte, _ protocol.Version) ([]byte, error) {
if len(f.Data) == 0 && !f.Fin {
return nil, errors.New("StreamFrame: attempting to write empty frame without FIN")
}
typ := byte(0x8)
if f.Fin {
typ ^= 0b1
}
hasOffset := f.Offset != 0
if f.DataLenPresent {
typ ^= 0b10
}
if hasOffset {
typ ^= 0b100
}
b = append(b, typ)
b = quicvarint.Append(b, uint64(f.StreamID))
if hasOffset {
b = quicvarint.Append(b, uint64(f.Offset))
}
if f.DataLenPresent {
b = quicvarint.Append(b, uint64(f.DataLen()))
}
b = append(b, f.Data...)
return b, nil
}
// Length returns the total length of the STREAM frame
func (f *StreamFrame) Length(protocol.Version) protocol.ByteCount {
length := 1 + quicvarint.Len(uint64(f.StreamID))
if f.Offset != 0 {
length += quicvarint.Len(uint64(f.Offset))
}
if f.DataLenPresent {
length += quicvarint.Len(uint64(f.DataLen()))
}
return protocol.ByteCount(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, _ protocol.Version) protocol.ByteCount {
headerLen := 1 + protocol.ByteCount(quicvarint.Len(uint64(f.StreamID)))
if f.Offset != 0 {
headerLen += protocol.ByteCount(quicvarint.Len(uint64(f.Offset)))
}
if f.DataLenPresent {
// Pretend that the data size will be 1 byte.
// If it turns out that varint encoding the length will consume 2 bytes, we need to adjust the data length afterward
headerLen++
}
if headerLen > maxSize {
return 0
}
maxDataLen := maxSize - headerLen
if f.DataLenPresent && quicvarint.Len(uint64(maxDataLen)) != 1 {
maxDataLen--
}
return maxDataLen
}
// MaybeSplitOffFrame splits a frame such that it is not bigger than n bytes.
// It returns if the frame was actually split.
// The frame might not be split if:
// * the size is large enough to fit the whole frame
// * the size is too small to fit even a 1-byte frame. In that case, the frame returned is nil.
func (f *StreamFrame) MaybeSplitOffFrame(maxSize protocol.ByteCount, version protocol.Version) (*StreamFrame, bool /* was splitting required */) {
if maxSize >= f.Length(version) {
return nil, false
}
n := f.MaxDataLen(maxSize, version)
if n == 0 {
return nil, true
}
new := GetStreamFrame()
new.StreamID = f.StreamID
new.Offset = f.Offset
new.Fin = false
new.DataLenPresent = f.DataLenPresent
// swap the data slices
new.Data, f.Data = f.Data, new.Data
new.fromPool, f.fromPool = f.fromPool, new.fromPool
f.Data = f.Data[:protocol.ByteCount(len(new.Data))-n]
copy(f.Data, new.Data[n:])
new.Data = new.Data[:n]
f.Offset += n
return new, true
}
func (f *StreamFrame) PutBack() {
putStreamFrame(f)
}
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