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simplify splitting of STREAM frames

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This commit is contained in:
Marten Seemann
2019-08-27 18:01:01 +07:00
parent 5fa38a83fa
commit 515c21dd1d
3 changed files with 45 additions and 39 deletions
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13
internal/wire/stream_frame.go
View File

@@ -143,15 +143,18 @@ func (f *StreamFrame) MaxDataLen(maxSize protocol.ByteCount, version protocol.Ve
}
// 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) {
// 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.VersionNumber) (*StreamFrame, bool /* was splitting required */) {
if maxSize >= f.Length(version) {
return nil, nil
return nil, false
}
n := f.MaxDataLen(maxSize, version)
if n == 0 {
return nil, errors.New("too small")
return nil, true
}
newFrame := &StreamFrame{
FinBit: false,
@@ -164,5 +167,5 @@ func (f *StreamFrame) MaybeSplitOffFrame(maxSize protocol.ByteCount, version pro
f.Data = f.Data[n:]
f.Offset += n
return newFrame, nil
return newFrame, true
}

61
internal/wire/stream_frame_test.go
View File

@@ -287,12 +287,13 @@ var _ = Describe("STREAM frame", func() {
Offset: 0xdeadbeef,
Data: make([]byte, 100),
}
newFrame, err := f.MaybeSplitOffFrame(f.Length(versionIETFFrames), versionIETFFrames)
Expect(err).ToNot(HaveOccurred())
Expect(newFrame).To(BeNil())
newFrame, err = f.MaybeSplitOffFrame(f.Length(versionIETFFrames)-1, versionIETFFrames)
Expect(err).ToNot(HaveOccurred())
Expect(newFrame).ToNot(BeNil())
frame, needsSplit := f.MaybeSplitOffFrame(f.Length(versionIETFFrames), versionIETFFrames)
Expect(needsSplit).To(BeFalse())
Expect(frame).To(BeNil())
Expect(f.DataLen()).To(BeEquivalentTo(100))
frame, needsSplit = f.MaybeSplitOffFrame(f.Length(versionIETFFrames)-1, versionIETFFrames)
Expect(needsSplit).To(BeTrue())
Expect(frame.DataLen()).To(BeEquivalentTo(99))
})
It("keeps the data len", func() {
@@ -301,11 +302,11 @@ var _ = Describe("STREAM frame", func() {
DataLenPresent: true,
Data: make([]byte, 100),
}
newFrame, err := f.MaybeSplitOffFrame(66, versionIETFFrames)
Expect(err).ToNot(HaveOccurred())
Expect(newFrame).ToNot(BeNil())
frame, needsSplit := f.MaybeSplitOffFrame(66, versionIETFFrames)
Expect(needsSplit).To(BeTrue())
Expect(frame).ToNot(BeNil())
Expect(f.DataLenPresent).To(BeTrue())
Expect(newFrame.DataLenPresent).To(BeTrue())
Expect(frame.DataLenPresent).To(BeTrue())
})
It("adjusts the offset", func() {
@@ -314,11 +315,11 @@ var _ = Describe("STREAM frame", func() {
Offset: 0x100,
Data: []byte("foobar"),
}
newFrame, err := f.MaybeSplitOffFrame(f.Length(versionIETFFrames)-3, versionIETFFrames)
Expect(err).ToNot(HaveOccurred())
Expect(newFrame).ToNot(BeNil())
Expect(newFrame.Offset).To(Equal(protocol.ByteCount(0x100)))
Expect(newFrame.Data).To(Equal([]byte("foo")))
frame, needsSplit := f.MaybeSplitOffFrame(f.Length(versionIETFFrames)-3, versionIETFFrames)
Expect(needsSplit).To(BeTrue())
Expect(frame).ToNot(BeNil())
Expect(frame.Offset).To(Equal(protocol.ByteCount(0x100)))
Expect(frame.Data).To(Equal([]byte("foo")))
Expect(f.Offset).To(Equal(protocol.ByteCount(0x100 + 3)))
Expect(f.Data).To(Equal([]byte("bar")))
})
@@ -330,12 +331,12 @@ var _ = Describe("STREAM frame", func() {
Offset: 0xdeadbeef,
Data: make([]byte, 100),
}
newFrame, err := f.MaybeSplitOffFrame(50, versionIETFFrames)
Expect(err).ToNot(HaveOccurred())
Expect(newFrame).ToNot(BeNil())
Expect(newFrame.Offset).To(BeNumerically("<", f.Offset))
frame, needsSplit := f.MaybeSplitOffFrame(50, versionIETFFrames)
Expect(needsSplit).To(BeTrue())
Expect(frame).ToNot(BeNil())
Expect(frame.Offset).To(BeNumerically("<", f.Offset))
Expect(f.FinBit).To(BeTrue())
Expect(newFrame.FinBit).To(BeFalse())
Expect(frame.FinBit).To(BeFalse())
})
It("produces frames of the correct length, without data len", func() {
@@ -347,14 +348,15 @@ var _ = Describe("STREAM frame", func() {
}
minFrameSize := f.Length(versionIETFFrames)
for i := protocol.ByteCount(0); i < minFrameSize; i++ {
_, err := f.MaybeSplitOffFrame(i, versionIETFFrames)
Expect(err).To(HaveOccurred())
f, needsSplit := f.MaybeSplitOffFrame(i, versionIETFFrames)
Expect(needsSplit).To(BeTrue())
Expect(f).To(BeNil())
}
for i := minFrameSize; i < size; i++ {
f.Data = make([]byte, size)
newFrame, err := f.MaybeSplitOffFrame(i, versionIETFFrames)
Expect(err).ToNot(HaveOccurred())
Expect(newFrame.Length(versionIETFFrames)).To(Equal(i))
f, needsSplit := f.MaybeSplitOffFrame(i, versionIETFFrames)
Expect(needsSplit).To(BeTrue())
Expect(f.Length(versionIETFFrames)).To(Equal(i))
}
})
@@ -368,14 +370,15 @@ var _ = Describe("STREAM frame", func() {
}
minFrameSize := f.Length(versionIETFFrames)
for i := protocol.ByteCount(0); i < minFrameSize; i++ {
_, err := f.MaybeSplitOffFrame(i, versionIETFFrames)
Expect(err).To(HaveOccurred())
f, needsSplit := f.MaybeSplitOffFrame(i, versionIETFFrames)
Expect(needsSplit).To(BeTrue())
Expect(f).To(BeNil())
}
var frameOneByteTooSmallCounter int
for i := minFrameSize; i < size; i++ {
f.Data = make([]byte, size)
newFrame, err := f.MaybeSplitOffFrame(i, versionIETFFrames)
Expect(err).ToNot(HaveOccurred())
newFrame, needsSplit := f.MaybeSplitOffFrame(i, versionIETFFrames)
Expect(needsSplit).To(BeTrue())
// There's *one* pathological case, where a data length of x can be encoded into 1 byte
// but a data lengths of x+1 needs 2 bytes
// In that case, it's impossible to create a STREAM frame of the desired size

10
packet_packer.go
View File

@@ -284,11 +284,11 @@ func (p *packetPacker) PackRetransmission(packet *ackhandler.Packet) ([]*packedP
frame.DataLenPresent = false
frameToAdd := frame
sf, err := frame.MaybeSplitOffFrame(maxSize-length, p.version)
if err != nil {
return nil, err
}
if sf != nil {
sf, needsSplit := frame.MaybeSplitOffFrame(maxSize-length, p.version)
if needsSplit {
if sf == nil { // size too small to create a new STREAM frame
continue
}
frameToAdd = sf
} else {
streamFrames = streamFrames[1:]