99 lines
2.6 KiB
Go
99 lines
2.6 KiB
Go
package wire
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import (
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"bytes"
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"io"
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"github.com/quic-go/quic-go/internal/protocol"
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"github.com/quic-go/quic-go/quicvarint"
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)
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// A CryptoFrame is a CRYPTO frame
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type CryptoFrame struct {
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Offset protocol.ByteCount
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Data []byte
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}
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func parseCryptoFrame(r *bytes.Reader, _ protocol.Version) (*CryptoFrame, error) {
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frame := &CryptoFrame{}
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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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frame.Offset = protocol.ByteCount(offset)
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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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if dataLen > uint64(r.Len()) {
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return nil, io.EOF
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}
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if dataLen != 0 {
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frame.Data = make([]byte, dataLen)
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if _, err := io.ReadFull(r, frame.Data); err != nil {
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// this should never happen, since we already checked the dataLen earlier
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return nil, err
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}
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}
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return frame, nil
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}
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func (f *CryptoFrame) Append(b []byte, _ protocol.Version) ([]byte, error) {
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b = append(b, cryptoFrameType)
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b = quicvarint.Append(b, uint64(f.Offset))
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b = quicvarint.Append(b, uint64(len(f.Data)))
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b = append(b, f.Data...)
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return b, nil
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}
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// Length of a written frame
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func (f *CryptoFrame) Length(_ protocol.Version) protocol.ByteCount {
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return 1 + quicvarint.Len(uint64(f.Offset)) + quicvarint.Len(uint64(len(f.Data))) + protocol.ByteCount(len(f.Data))
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}
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// MaxDataLen returns the maximum data length
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func (f *CryptoFrame) MaxDataLen(maxSize protocol.ByteCount) protocol.ByteCount {
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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 := 1 + quicvarint.Len(uint64(f.Offset)) + 1
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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 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 *CryptoFrame) MaybeSplitOffFrame(maxSize protocol.ByteCount, version protocol.Version) (*CryptoFrame, bool /* was splitting required */) {
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if f.Length(version) <= maxSize {
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return nil, false
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}
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n := f.MaxDataLen(maxSize)
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if n == 0 {
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return nil, true
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}
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newLen := protocol.ByteCount(len(f.Data)) - n
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new := &CryptoFrame{}
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new.Offset = f.Offset
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new.Data = make([]byte, newLen)
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// swap the data slices
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new.Data, f.Data = f.Data, new.Data
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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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