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

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

@@ -0,0 +1,271 @@
+package qpack
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"sync"
+
+	"golang.org/x/net/http2/hpack"
+)
+
+// A decodingError is something the spec defines as a decoding error.
+type decodingError struct {
+	err error
+}
+
+func (de decodingError) Error() string {
+	return fmt.Sprintf("decoding error: %v", de.err)
+}
+
+// An invalidIndexError is returned when an encoder references a table
+// entry before the static table or after the end of the dynamic table.
+type invalidIndexError int
+
+func (e invalidIndexError) Error() string {
+	return fmt.Sprintf("invalid indexed representation index %d", int(e))
+}
+
+var errNoDynamicTable = decodingError{errors.New("no dynamic table")}
+
+// errNeedMore is an internal sentinel error value that means the
+// buffer is truncated and we need to read more data before we can
+// continue parsing.
+var errNeedMore = errors.New("need more data")
+
+// A Decoder is the decoding context for incremental processing of
+// header blocks.
+type Decoder struct {
+	mutex sync.Mutex
+
+	emitFunc func(f HeaderField)
+
+	readRequiredInsertCount bool
+	readDeltaBase           bool
+
+	// buf is the unparsed buffer. It's only written to
+	// saveBuf if it was truncated in the middle of a header
+	// block. Because it's usually not owned, we can only
+	// process it under Write.
+	buf []byte // not owned; only valid during Write
+
+	// saveBuf is previous data passed to Write which we weren't able
+	// to fully parse before. Unlike buf, we own this data.
+	saveBuf bytes.Buffer
+}
+
+// NewDecoder returns a new decoder
+// The emitFunc will be called for each valid field parsed,
+// in the same goroutine as calls to Write, before Write returns.
+func NewDecoder(emitFunc func(f HeaderField)) *Decoder {
+	return &Decoder{emitFunc: emitFunc}
+}
+
+func (d *Decoder) Write(p []byte) (int, error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+
+	d.mutex.Lock()
+	n, err := d.writeLocked(p)
+	d.mutex.Unlock()
+	return n, err
+}
+
+func (d *Decoder) writeLocked(p []byte) (int, error) {
+	// Only copy the data if we have to. Optimistically assume
+	// that p will contain a complete header block.
+	if d.saveBuf.Len() == 0 {
+		d.buf = p
+	} else {
+		d.saveBuf.Write(p)
+		d.buf = d.saveBuf.Bytes()
+		d.saveBuf.Reset()
+	}
+
+	if err := d.decode(); err != nil {
+		if err != errNeedMore {
+			return 0, err
+		}
+		// TODO: limit the size of the buffer
+		d.saveBuf.Write(d.buf)
+	}
+	return len(p), nil
+}
+
+// DecodeFull decodes an entire block.
+func (d *Decoder) DecodeFull(p []byte) ([]HeaderField, error) {
+	if len(p) == 0 {
+		return []HeaderField{}, nil
+	}
+
+	d.mutex.Lock()
+	defer d.mutex.Unlock()
+
+	saveFunc := d.emitFunc
+	defer func() { d.emitFunc = saveFunc }()
+
+	var hf []HeaderField
+	d.emitFunc = func(f HeaderField) { hf = append(hf, f) }
+	if _, err := d.writeLocked(p); err != nil {
+		return nil, err
+	}
+	if err := d.Close(); err != nil {
+		return nil, err
+	}
+	return hf, nil
+}
+
+// Close declares that the decoding is complete and resets the Decoder
+// to be reused again for a new header block. If there is any remaining
+// data in the decoder's buffer, Close returns an error.
+func (d *Decoder) Close() error {
+	if d.saveBuf.Len() > 0 {
+		d.saveBuf.Reset()
+		return decodingError{errors.New("truncated headers")}
+	}
+	d.readRequiredInsertCount = false
+	d.readDeltaBase = false
+	return nil
+}
+
+func (d *Decoder) decode() error {
+	if !d.readRequiredInsertCount {
+		requiredInsertCount, rest, err := readVarInt(8, d.buf)
+		if err != nil {
+			return err
+		}
+		d.readRequiredInsertCount = true
+		if requiredInsertCount != 0 {
+			return decodingError{errors.New("expected Required Insert Count to be zero")}
+		}
+		d.buf = rest
+	}
+	if !d.readDeltaBase {
+		base, rest, err := readVarInt(7, d.buf)
+		if err != nil {
+			return err
+		}
+		d.readDeltaBase = true
+		if base != 0 {
+			return decodingError{errors.New("expected Base to be zero")}
+		}
+		d.buf = rest
+	}
+	if len(d.buf) == 0 {
+		return errNeedMore
+	}
+
+	for len(d.buf) > 0 {
+		b := d.buf[0]
+		var err error
+		switch {
+		case b&0x80 > 0: // 1xxxxxxx
+			err = d.parseIndexedHeaderField()
+		case b&0xc0 == 0x40: // 01xxxxxx
+			err = d.parseLiteralHeaderField()
+		case b&0xe0 == 0x20: // 001xxxxx
+			err = d.parseLiteralHeaderFieldWithoutNameReference()
+		default:
+			err = fmt.Errorf("unexpected type byte: %#x", b)
+		}
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (d *Decoder) parseIndexedHeaderField() error {
+	buf := d.buf
+	if buf[0]&0x40 == 0 {
+		return errNoDynamicTable
+	}
+	index, buf, err := readVarInt(6, buf)
+	if err != nil {
+		return err
+	}
+	hf, ok := d.at(index)
+	if !ok {
+		return decodingError{invalidIndexError(index)}
+	}
+	d.emitFunc(hf)
+	d.buf = buf
+	return nil
+}
+
+func (d *Decoder) parseLiteralHeaderField() error {
+	buf := d.buf
+	if buf[0]&0x20 > 0 || buf[0]&0x10 == 0 {
+		return errNoDynamicTable
+	}
+	index, buf, err := readVarInt(4, buf)
+	if err != nil {
+		return err
+	}
+	hf, ok := d.at(index)
+	if !ok {
+		return decodingError{invalidIndexError(index)}
+	}
+	if len(buf) == 0 {
+		return errNeedMore
+	}
+	usesHuffman := buf[0]&0x80 > 0
+	val, buf, err := d.readString(buf, 7, usesHuffman)
+	if err != nil {
+		return err
+	}
+	hf.Value = val
+	d.emitFunc(hf)
+	d.buf = buf
+	return nil
+}
+
+func (d *Decoder) parseLiteralHeaderFieldWithoutNameReference() error {
+	buf := d.buf
+	usesHuffmanForName := buf[0]&0x8 > 0
+	name, buf, err := d.readString(buf, 3, usesHuffmanForName)
+	if err != nil {
+		return err
+	}
+	if len(buf) == 0 {
+		return errNeedMore
+	}
+	usesHuffmanForVal := buf[0]&0x80 > 0
+	val, buf, err := d.readString(buf, 7, usesHuffmanForVal)
+	if err != nil {
+		return err
+	}
+	d.emitFunc(HeaderField{Name: name, Value: val})
+	d.buf = buf
+	return nil
+}
+
+func (d *Decoder) readString(buf []byte, n uint8, usesHuffman bool) (string, []byte, error) {
+	l, buf, err := readVarInt(n, buf)
+	if err != nil {
+		return "", nil, err
+	}
+	if uint64(len(buf)) < l {
+		return "", nil, errNeedMore
+	}
+	var val string
+	if usesHuffman {
+		var err error
+		val, err = hpack.HuffmanDecodeToString(buf[:l])
+		if err != nil {
+			return "", nil, err
+		}
+	} else {
+		val = string(buf[:l])
+	}
+	buf = buf[l:]
+	return val, buf, nil
+}
+
+func (d *Decoder) at(i uint64) (hf HeaderField, ok bool) {
+	if i >= uint64(len(staticTableEntries)) {
+		return
+	}
+	return staticTableEntries[i], true
+}