vendor: update golang.org/x/net/http2/hpack

Updates bundled golang.org/x/net/http2/hpack to x/net git rev 22bb95c5e for:

   http2/hpack: lazily build huffman table on first use
   https://golang.org/cl/127275

   http2/hpack: reduce memory for huffman decoding table
   https://golang.org/cl/127235

   http2/hpack: dynamic table updates must occur first
   https://golang.org/cl/111681

And a typo & gofmt CL.

Updates #25023

Change-Id: I7027fdb4982305aa671d811fe87f61e5df0f8e0e
Reviewed-on: https://go-review.googlesource.com/127355
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/vendor/golang_org/x/net/http2/hpack/encode.go

@@ -206,7 +206,7 @@ func appendVarInt(dst []byte, n byte, i uint64) []byte {
 }
 
 // appendHpackString appends s, as encoded in "String Literal"
-// representation, to dst and returns the the extended buffer.
+// representation, to dst and returns the extended buffer.
 //
 // s will be encoded in Huffman codes only when it produces strictly
 // shorter byte string.

src/vendor/golang_org/x/net/http2/hpack/hpack.go

@@ -389,6 +389,12 @@ func (d *Decoder) callEmit(hf HeaderField) error {
 
 // (same invariants and behavior as parseHeaderFieldRepr)
 func (d *Decoder) parseDynamicTableSizeUpdate() error {
+	// RFC 7541, sec 4.2: This dynamic table size update MUST occur at the
+	// beginning of the first header block following the change to the dynamic table size.
+	if d.dynTab.size > 0 {
+		return DecodingError{errors.New("dynamic table size update MUST occur at the beginning of a header block")}
+	}
+
 	buf := d.buf
 	size, buf, err := readVarInt(5, buf)
 	if err != nil {

src/vendor/golang_org/x/net/http2/hpack/hpack_test.go

@@ -462,6 +462,27 @@ func TestHuffmanDecode(t *testing.T) {
 	}
 }
 
+func BenchmarkHuffmanDecode(b *testing.B) {
+	b.StopTimer()
+	enc, err := hex.DecodeString(strings.Replace("94e7 821d d7f2 e6c7 b335 dfdf cd5b 3960 d5af 2708 7f36 72c1 ab27 0fb5 291f 9587 3160 65c0 03ed 4ee5 b106 3d50 07",
+		" ", "", -1))
+	if err != nil {
+		b.Fatal(err)
+	}
+	b.ReportAllocs()
+	b.StartTimer()
+	var buf bytes.Buffer
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		if _, err := HuffmanDecode(&buf, enc); err != nil {
+			b.Fatalf("decode error: %v", err)
+		}
+		if string(buf.Bytes()) != "foo=ASDJKHQKBZXOQWEOPIUAXQWEOIU; max-age=3600; version=1" {
+			b.Fatalf("bogus output %q", buf.Bytes())
+		}
+	}
+}
+
 func TestAppendHuffmanString(t *testing.T) {
 	tests := []struct {
 		in, want string
@@ -720,3 +741,22 @@ func TestSaveBufLimit(t *testing.T) {
 		t.Fatalf("Write error = %v; want ErrStringLength", err)
 	}
 }
+
+func TestDynamicSizeUpdate(t *testing.T) {
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	enc.SetMaxDynamicTableSize(255)
+	enc.WriteField(HeaderField{Name: "foo", Value: "bar"})
+
+	d := NewDecoder(4096, nil)
+	_, err := d.DecodeFull(buf.Bytes())
+	if err != nil {
+		t.Fatalf("unexpected error: got = %v", err)
+	}
+
+	// must fail since the dynamic table update must be at the beginning
+	_, err = d.DecodeFull(buf.Bytes())
+	if err == nil {
+		t.Fatalf("dynamic table size update not at the beginning of a header block")
+	}
+}

src/vendor/golang_org/x/net/http2/hpack/huffman.go

@@ -47,6 +47,7 @@ var ErrInvalidHuffman = errors.New("hpack: invalid Huffman-encoded data")
 // If maxLen is greater than 0, attempts to write more to buf than
 // maxLen bytes will return ErrStringLength.
 func huffmanDecode(buf *bytes.Buffer, maxLen int, v []byte) error {
+	rootHuffmanNode := getRootHuffmanNode()
 	n := rootHuffmanNode
 	// cur is the bit buffer that has not been fed into n.
 	// cbits is the number of low order bits in cur that are valid.
@@ -106,7 +107,7 @@ func huffmanDecode(buf *bytes.Buffer, maxLen int, v []byte) error {
 
 type node struct {
 	// children is non-nil for internal nodes
-	children []*node
+	children *[256]*node
 
 	// The following are only valid if children is nil:
 	codeLen uint8 // number of bits that led to the output of sym
@@ -114,22 +115,31 @@ type node struct {
 }
 
 func newInternalNode() *node {
-	return &node{children: make([]*node, 256)}
+	return &node{children: new([256]*node)}
 }
 
-var rootHuffmanNode = newInternalNode()
+var (
+	buildRootOnce       sync.Once
+	lazyRootHuffmanNode *node
+)
+
+func getRootHuffmanNode() *node {
+	buildRootOnce.Do(buildRootHuffmanNode)
+	return lazyRootHuffmanNode
+}
 
-func init() {
+func buildRootHuffmanNode() {
 	if len(huffmanCodes) != 256 {
 		panic("unexpected size")
 	}
+	lazyRootHuffmanNode = newInternalNode()
 	for i, code := range huffmanCodes {
 		addDecoderNode(byte(i), code, huffmanCodeLen[i])
 	}
 }
 
 func addDecoderNode(sym byte, code uint32, codeLen uint8) {
-	cur := rootHuffmanNode
+	cur := lazyRootHuffmanNode
 	for codeLen > 8 {
 		codeLen -= 8
 		i := uint8(code >> codeLen)

src/vendor/golang_org/x/net/http2/hpack/tables.go

@@ -128,67 +128,67 @@ func (t *headerFieldTable) idToIndex(id uint64) uint64 {
 // http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-07#appendix-B
 var staticTable = newStaticTable()
 var staticTableEntries = [...]HeaderField{
-	HeaderField{Name: ":authority"},
-	HeaderField{Name: ":method", Value: "GET"},
-	HeaderField{Name: ":method", Value: "POST"},
-	HeaderField{Name: ":path", Value: "/"},
-	HeaderField{Name: ":path", Value: "/index.html"},
-	HeaderField{Name: ":scheme", Value: "http"},
-	HeaderField{Name: ":scheme", Value: "https"},
-	HeaderField{Name: ":status", Value: "200"},
-	HeaderField{Name: ":status", Value: "204"},
-	HeaderField{Name: ":status", Value: "206"},
-	HeaderField{Name: ":status", Value: "304"},
-	HeaderField{Name: ":status", Value: "400"},
-	HeaderField{Name: ":status", Value: "404"},
-	HeaderField{Name: ":status", Value: "500"},
-	HeaderField{Name: "accept-charset"},
-	HeaderField{Name: "accept-encoding", Value: "gzip, deflate"},
-	HeaderField{Name: "accept-language"},
-	HeaderField{Name: "accept-ranges"},
-	HeaderField{Name: "accept"},
-	HeaderField{Name: "access-control-allow-origin"},
-	HeaderField{Name: "age"},
-	HeaderField{Name: "allow"},
-	HeaderField{Name: "authorization"},
-	HeaderField{Name: "cache-control"},
-	HeaderField{Name: "content-disposition"},
-	HeaderField{Name: "content-encoding"},
-	HeaderField{Name: "content-language"},
-	HeaderField{Name: "content-length"},
-	HeaderField{Name: "content-location"},
-	HeaderField{Name: "content-range"},
-	HeaderField{Name: "content-type"},
-	HeaderField{Name: "cookie"},
-	HeaderField{Name: "date"},
-	HeaderField{Name: "etag"},
-	HeaderField{Name: "expect"},
-	HeaderField{Name: "expires"},
-	HeaderField{Name: "from"},
-	HeaderField{Name: "host"},
-	HeaderField{Name: "if-match"},
-	HeaderField{Name: "if-modified-since"},
-	HeaderField{Name: "if-none-match"},
-	HeaderField{Name: "if-range"},
-	HeaderField{Name: "if-unmodified-since"},
-	HeaderField{Name: "last-modified"},
-	HeaderField{Name: "link"},
-	HeaderField{Name: "location"},
-	HeaderField{Name: "max-forwards"},
-	HeaderField{Name: "proxy-authenticate"},
-	HeaderField{Name: "proxy-authorization"},
-	HeaderField{Name: "range"},
-	HeaderField{Name: "referer"},
-	HeaderField{Name: "refresh"},
-	HeaderField{Name: "retry-after"},
-	HeaderField{Name: "server"},
-	HeaderField{Name: "set-cookie"},
-	HeaderField{Name: "strict-transport-security"},
-	HeaderField{Name: "transfer-encoding"},
-	HeaderField{Name: "user-agent"},
-	HeaderField{Name: "vary"},
-	HeaderField{Name: "via"},
-	HeaderField{Name: "www-authenticate"},
+	{Name: ":authority"},
+	{Name: ":method", Value: "GET"},
+	{Name: ":method", Value: "POST"},
+	{Name: ":path", Value: "/"},
+	{Name: ":path", Value: "/index.html"},
+	{Name: ":scheme", Value: "http"},
+	{Name: ":scheme", Value: "https"},
+	{Name: ":status", Value: "200"},
+	{Name: ":status", Value: "204"},
+	{Name: ":status", Value: "206"},
+	{Name: ":status", Value: "304"},
+	{Name: ":status", Value: "400"},
+	{Name: ":status", Value: "404"},
+	{Name: ":status", Value: "500"},
+	{Name: "accept-charset"},
+	{Name: "accept-encoding", Value: "gzip, deflate"},
+	{Name: "accept-language"},
+	{Name: "accept-ranges"},
+	{Name: "accept"},
+	{Name: "access-control-allow-origin"},
+	{Name: "age"},
+	{Name: "allow"},
+	{Name: "authorization"},
+	{Name: "cache-control"},
+	{Name: "content-disposition"},
+	{Name: "content-encoding"},
+	{Name: "content-language"},
+	{Name: "content-length"},
+	{Name: "content-location"},
+	{Name: "content-range"},
+	{Name: "content-type"},
+	{Name: "cookie"},
+	{Name: "date"},
+	{Name: "etag"},
+	{Name: "expect"},
+	{Name: "expires"},
+	{Name: "from"},
+	{Name: "host"},
+	{Name: "if-match"},
+	{Name: "if-modified-since"},
+	{Name: "if-none-match"},
+	{Name: "if-range"},
+	{Name: "if-unmodified-since"},
+	{Name: "last-modified"},
+	{Name: "link"},
+	{Name: "location"},
+	{Name: "max-forwards"},
+	{Name: "proxy-authenticate"},
+	{Name: "proxy-authorization"},
+	{Name: "range"},
+	{Name: "referer"},
+	{Name: "refresh"},
+	{Name: "retry-after"},
+	{Name: "server"},
+	{Name: "set-cookie"},
+	{Name: "strict-transport-security"},
+	{Name: "transfer-encoding"},
+	{Name: "user-agent"},
+	{Name: "vary"},
+	{Name: "via"},
+	{Name: "www-authenticate"},
 }
 
 func newStaticTable() *headerFieldTable {