migrate to go modules from vndr

Signed-off-by: Tariq Ibrahim <tariq181290@gmail.com>

vendor/golang.org/x/net/http2/hpack/huffman.go

@@ -47,13 +47,18 @@ 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, nbits := uint(0), uint8(0)
+	// 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.
+	// sbits is the number of bits of the symbol prefix being decoded.
+	cur, cbits, sbits := uint(0), uint8(0), uint8(0)
 	for _, b := range v {
 		cur = cur<<8 | uint(b)
-		nbits += 8
-		for nbits >= 8 {
-			idx := byte(cur >> (nbits - 8))
+		cbits += 8
+		sbits += 8
+		for cbits >= 8 {
+			idx := byte(cur >> (cbits - 8))
 			n = n.children[idx]
 			if n == nil {
 				return ErrInvalidHuffman
@@ -63,28 +68,46 @@ func huffmanDecode(buf *bytes.Buffer, maxLen int, v []byte) error {
 					return ErrStringLength
 				}
 				buf.WriteByte(n.sym)
-				nbits -= n.codeLen
+				cbits -= n.codeLen
 				n = rootHuffmanNode
+				sbits = cbits
 			} else {
-				nbits -= 8
+				cbits -= 8
 			}
 		}
 	}
-	for nbits > 0 {
-		n = n.children[byte(cur<<(8-nbits))]
-		if n.children != nil || n.codeLen > nbits {
+	for cbits > 0 {
+		n = n.children[byte(cur<<(8-cbits))]
+		if n == nil {
+			return ErrInvalidHuffman
+		}
+		if n.children != nil || n.codeLen > cbits {
 			break
 		}
+		if maxLen != 0 && buf.Len() == maxLen {
+			return ErrStringLength
+		}
 		buf.WriteByte(n.sym)
-		nbits -= n.codeLen
+		cbits -= n.codeLen
 		n = rootHuffmanNode
+		sbits = cbits
 	}
+	if sbits > 7 {
+		// Either there was an incomplete symbol, or overlong padding.
+		// Both are decoding errors per RFC 7541 section 5.2.
+		return ErrInvalidHuffman
+	}
+	if mask := uint(1<<cbits - 1); cur&mask != mask {
+		// Trailing bits must be a prefix of EOS per RFC 7541 section 5.2.
+		return ErrInvalidHuffman
+	}
+
 	return nil
 }
 
 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
@@ -92,22 +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 init() {
+func getRootHuffmanNode() *node {
+	buildRootOnce.Do(buildRootHuffmanNode)
+	return lazyRootHuffmanNode
+}
+
+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)