1package wire
2
3import (
4	"bytes"
5	"errors"
6	"io"
7
8	"github.com/lucas-clemente/quic-go/internal/protocol"
9	"github.com/lucas-clemente/quic-go/quicvarint"
10)
11
12// A StreamFrame of QUIC
13type StreamFrame struct {
14	StreamID       protocol.StreamID
15	Offset         protocol.ByteCount
16	Data           []byte
17	Fin            bool
18	DataLenPresent bool
19
20	fromPool bool
21}
22
23func parseStreamFrame(r *bytes.Reader, _ protocol.VersionNumber) (*StreamFrame, error) {
24	typeByte, err := r.ReadByte()
25	if err != nil {
26		return nil, err
27	}
28
29	hasOffset := typeByte&0x4 > 0
30	fin := typeByte&0x1 > 0
31	hasDataLen := typeByte&0x2 > 0
32
33	streamID, err := quicvarint.Read(r)
34	if err != nil {
35		return nil, err
36	}
37	var offset uint64
38	if hasOffset {
39		offset, err = quicvarint.Read(r)
40		if err != nil {
41			return nil, err
42		}
43	}
44
45	var dataLen uint64
46	if hasDataLen {
47		var err error
48		dataLen, err = quicvarint.Read(r)
49		if err != nil {
50			return nil, err
51		}
52	} else {
53		// The rest of the packet is data
54		dataLen = uint64(r.Len())
55	}
56
57	var frame *StreamFrame
58	if dataLen < protocol.MinStreamFrameBufferSize {
59		frame = &StreamFrame{Data: make([]byte, dataLen)}
60	} else {
61		frame = GetStreamFrame()
62		// The STREAM frame can't be larger than the StreamFrame we obtained from the buffer,
63		// since those StreamFrames have a buffer length of the maximum packet size.
64		if dataLen > uint64(cap(frame.Data)) {
65			return nil, io.EOF
66		}
67		frame.Data = frame.Data[:dataLen]
68	}
69
70	frame.StreamID = protocol.StreamID(streamID)
71	frame.Offset = protocol.ByteCount(offset)
72	frame.Fin = fin
73	frame.DataLenPresent = hasDataLen
74
75	if dataLen != 0 {
76		if _, err := io.ReadFull(r, frame.Data); err != nil {
77			return nil, err
78		}
79	}
80	if frame.Offset+frame.DataLen() > protocol.MaxByteCount {
81		return nil, errors.New("stream data overflows maximum offset")
82	}
83	return frame, nil
84}
85
86// Write writes a STREAM frame
87func (f *StreamFrame) Write(b *bytes.Buffer, version protocol.VersionNumber) error {
88	if len(f.Data) == 0 && !f.Fin {
89		return errors.New("StreamFrame: attempting to write empty frame without FIN")
90	}
91
92	typeByte := byte(0x8)
93	if f.Fin {
94		typeByte ^= 0x1
95	}
96	hasOffset := f.Offset != 0
97	if f.DataLenPresent {
98		typeByte ^= 0x2
99	}
100	if hasOffset {
101		typeByte ^= 0x4
102	}
103	b.WriteByte(typeByte)
104	quicvarint.Write(b, uint64(f.StreamID))
105	if hasOffset {
106		quicvarint.Write(b, uint64(f.Offset))
107	}
108	if f.DataLenPresent {
109		quicvarint.Write(b, uint64(f.DataLen()))
110	}
111	b.Write(f.Data)
112	return nil
113}
114
115// Length returns the total length of the STREAM frame
116func (f *StreamFrame) Length(version protocol.VersionNumber) protocol.ByteCount {
117	length := 1 + quicvarint.Len(uint64(f.StreamID))
118	if f.Offset != 0 {
119		length += quicvarint.Len(uint64(f.Offset))
120	}
121	if f.DataLenPresent {
122		length += quicvarint.Len(uint64(f.DataLen()))
123	}
124	return length + f.DataLen()
125}
126
127// DataLen gives the length of data in bytes
128func (f *StreamFrame) DataLen() protocol.ByteCount {
129	return protocol.ByteCount(len(f.Data))
130}
131
132// MaxDataLen returns the maximum data length
133// If 0 is returned, writing will fail (a STREAM frame must contain at least 1 byte of data).
134func (f *StreamFrame) MaxDataLen(maxSize protocol.ByteCount, version protocol.VersionNumber) protocol.ByteCount {
135	headerLen := 1 + quicvarint.Len(uint64(f.StreamID))
136	if f.Offset != 0 {
137		headerLen += quicvarint.Len(uint64(f.Offset))
138	}
139	if f.DataLenPresent {
140		// pretend that the data size will be 1 bytes
141		// if it turns out that varint encoding the length will consume 2 bytes, we need to adjust the data length afterwards
142		headerLen++
143	}
144	if headerLen > maxSize {
145		return 0
146	}
147	maxDataLen := maxSize - headerLen
148	if f.DataLenPresent && quicvarint.Len(uint64(maxDataLen)) != 1 {
149		maxDataLen--
150	}
151	return maxDataLen
152}
153
154// MaybeSplitOffFrame splits a frame such that it is not bigger than n bytes.
155// It returns if the frame was actually split.
156// The frame might not be split if:
157// * the size is large enough to fit the whole frame
158// * the size is too small to fit even a 1-byte frame. In that case, the frame returned is nil.
159func (f *StreamFrame) MaybeSplitOffFrame(maxSize protocol.ByteCount, version protocol.VersionNumber) (*StreamFrame, bool /* was splitting required */) {
160	if maxSize >= f.Length(version) {
161		return nil, false
162	}
163
164	n := f.MaxDataLen(maxSize, version)
165	if n == 0 {
166		return nil, true
167	}
168
169	new := GetStreamFrame()
170	new.StreamID = f.StreamID
171	new.Offset = f.Offset
172	new.Fin = false
173	new.DataLenPresent = f.DataLenPresent
174
175	// swap the data slices
176	new.Data, f.Data = f.Data, new.Data
177	new.fromPool, f.fromPool = f.fromPool, new.fromPool
178
179	f.Data = f.Data[:protocol.ByteCount(len(new.Data))-n]
180	copy(f.Data, new.Data[n:])
181	new.Data = new.Data[:n]
182	f.Offset += n
183
184	return new, true
185}
186
187func (f *StreamFrame) PutBack() {
188	putStreamFrame(f)
189}
190