Update quic-go dependency to support go 1.20 (#2292)

vendor/github.com/quic-go/qpack/encoder.go

@@ -0,0 +1,95 @@
+package qpack
+
+import (
+	"io"
+
+	"golang.org/x/net/http2/hpack"
+)
+
+// An Encoder performs QPACK encoding.
+type Encoder struct {
+	wrotePrefix bool
+
+	w   io.Writer
+	buf []byte
+}
+
+// NewEncoder returns a new Encoder which performs QPACK encoding. An
+// encoded data is written to w.
+func NewEncoder(w io.Writer) *Encoder {
+	return &Encoder{w: w}
+}
+
+// WriteField encodes f into a single Write to e's underlying Writer.
+// This function may also produce bytes for the Header Block Prefix
+// if necessary. If produced, it is done before encoding f.
+func (e *Encoder) WriteField(f HeaderField) error {
+	// write the Header Block Prefix
+	if !e.wrotePrefix {
+		e.buf = appendVarInt(e.buf, 8, 0)
+		e.buf = appendVarInt(e.buf, 7, 0)
+		e.wrotePrefix = true
+	}
+
+	idxAndVals, nameFound := encoderMap[f.Name]
+	if nameFound {
+		if idxAndVals.values == nil {
+			if len(f.Value) == 0 {
+				e.writeIndexedField(idxAndVals.idx)
+			} else {
+				e.writeLiteralFieldWithNameReference(&f, idxAndVals.idx)
+			}
+		} else {
+			valIdx, valueFound := idxAndVals.values[f.Value]
+			if valueFound {
+				e.writeIndexedField(valIdx)
+			} else {
+				e.writeLiteralFieldWithNameReference(&f, idxAndVals.idx)
+			}
+		}
+	} else {
+		e.writeLiteralFieldWithoutNameReference(f)
+	}
+
+	_, err := e.w.Write(e.buf)
+	e.buf = e.buf[:0]
+	return err
+}
+
+// Close declares that the encoding is complete and resets the Encoder
+// to be reused again for a new header block.
+func (e *Encoder) Close() error {
+	e.wrotePrefix = false
+	return nil
+}
+
+func (e *Encoder) writeLiteralFieldWithoutNameReference(f HeaderField) {
+	offset := len(e.buf)
+	e.buf = appendVarInt(e.buf, 3, hpack.HuffmanEncodeLength(f.Name))
+	e.buf[offset] ^= 0x20 ^ 0x8
+	e.buf = hpack.AppendHuffmanString(e.buf, f.Name)
+	offset = len(e.buf)
+	e.buf = appendVarInt(e.buf, 7, hpack.HuffmanEncodeLength(f.Value))
+	e.buf[offset] ^= 0x80
+	e.buf = hpack.AppendHuffmanString(e.buf, f.Value)
+}
+
+// Encodes a header field whose name is present in one of the tables.
+func (e *Encoder) writeLiteralFieldWithNameReference(f *HeaderField, id uint8) {
+	offset := len(e.buf)
+	e.buf = appendVarInt(e.buf, 4, uint64(id))
+	// Set the 01NTxxxx pattern, forcing N to 0 and T to 1
+	e.buf[offset] ^= 0x50
+	offset = len(e.buf)
+	e.buf = appendVarInt(e.buf, 7, hpack.HuffmanEncodeLength(f.Value))
+	e.buf[offset] ^= 0x80
+	e.buf = hpack.AppendHuffmanString(e.buf, f.Value)
+}
+
+// Encodes an indexed field, meaning it's entirely defined in one of the tables.
+func (e *Encoder) writeIndexedField(id uint8) {
+	offset := len(e.buf)
+	e.buf = appendVarInt(e.buf, 6, uint64(id))
+	// Set the 1Txxxxxx pattern, forcing T to 1
+	e.buf[offset] ^= 0xc0
+}