1 files changed, 226 insertions, 0 deletions
diff --git a/vendor/golang.org/x/net/http2/hpack/huffman.go b/vendor/golang.org/x/net/http2/hpack/huffman.go
new file mode 100644
index 000000000..20d083a71
--- /dev/null
+++ b/vendor/golang.org/x/net/http2/hpack/huffman.go
@@ -0,0 +1,226 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package hpack
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"sync"
+)
+
+var bufPool = sync.Pool{
+	New: func() interface{} { return new(bytes.Buffer) },
+}
+
+// HuffmanDecode decodes the string in v and writes the expanded
+// result to w, returning the number of bytes written to w and the
+// Write call's return value. At most one Write call is made.
+func HuffmanDecode(w io.Writer, v []byte) (int, error) {
+	buf := bufPool.Get().(*bytes.Buffer)
+	buf.Reset()
+	defer bufPool.Put(buf)
+	if err := huffmanDecode(buf, 0, v); err != nil {
+		return 0, err
+	}
+	return w.Write(buf.Bytes())
+}
+
+// HuffmanDecodeToString decodes the string in v.
+func HuffmanDecodeToString(v []byte) (string, error) {
+	buf := bufPool.Get().(*bytes.Buffer)
+	buf.Reset()
+	defer bufPool.Put(buf)
+	if err := huffmanDecode(buf, 0, v); err != nil {
+		return "", err
+	}
+	return buf.String(), nil
+}
+
+// ErrInvalidHuffman is returned for errors found decoding
+// Huffman-encoded strings.
+var ErrInvalidHuffman = errors.New("hpack: invalid Huffman-encoded data")
+
+// huffmanDecode decodes v to buf.
+// 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.
+	// 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)
+		cbits += 8
+		sbits += 8
+		for cbits >= 8 {
+			idx := byte(cur >> (cbits - 8))
+			n = n.children[idx]
+			if n == nil {
+				return ErrInvalidHuffman
+			}
+			if n.children == nil {
+				if maxLen != 0 && buf.Len() == maxLen {
+					return ErrStringLength
+				}
+				buf.WriteByte(n.sym)
+				cbits -= n.codeLen
+				n = rootHuffmanNode
+				sbits = cbits
+			} else {
+				cbits -= 8
+			}
+		}
+	}
+	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)
+		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
+}
+
+// incomparable is a zero-width, non-comparable type. Adding it to a struct
+// makes that struct also non-comparable, and generally doesn't add
+// any size (as long as it's first).
+type incomparable [0]func()
+
+type node struct {
+	_ incomparable
+
+	// children is non-nil for internal nodes
+	children *[256]*node
+
+	// The following are only valid if children is nil:
+	codeLen uint8 // number of bits that led to the output of sym
+	sym     byte  // output symbol
+}
+
+func newInternalNode() *node {
+	return &node{children: new([256]*node)}
+}
+
+var (
+	buildRootOnce       sync.Once
+	lazyRootHuffmanNode *node
+)
+
+func getRootHuffmanNode() *node {
+	buildRootOnce.Do(buildRootHuffmanNode)
+	return lazyRootHuffmanNode
+}
+
+func buildRootHuffmanNode() {
+	if len(huffmanCodes) != 256 {
+		panic("unexpected size")
+	}
+	lazyRootHuffmanNode = newInternalNode()
+	// allocate a leaf node for each of the 256 symbols
+	leaves := new([256]node)
+
+	for sym, code := range huffmanCodes {
+		codeLen := huffmanCodeLen[sym]
+
+		cur := lazyRootHuffmanNode
+		for codeLen > 8 {
+			codeLen -= 8
+			i := uint8(code >> codeLen)
+			if cur.children[i] == nil {
+				cur.children[i] = newInternalNode()
+			}
+			cur = cur.children[i]
+		}
+		shift := 8 - codeLen
+		start, end := int(uint8(code<<shift)), int(1<<shift)
+
+		leaves[sym].sym = byte(sym)
+		leaves[sym].codeLen = codeLen
+		for i := start; i < start+end; i++ {
+			cur.children[i] = &leaves[sym]
+		}
+	}
+}
+
+// AppendHuffmanString appends s, as encoded in Huffman codes, to dst
+// and returns the extended buffer.
+func AppendHuffmanString(dst []byte, s string) []byte {
+	// This relies on the maximum huffman code length being 30 (See tables.go huffmanCodeLen array)
+	// So if a uint64 buffer has less than 32 valid bits can always accommodate another huffmanCode.
+	var (
+		x uint64 // buffer
+		n uint   // number valid of bits present in x
+	)
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		n += uint(huffmanCodeLen[c])
+		x <<= huffmanCodeLen[c] % 64
+		x |= uint64(huffmanCodes[c])
+		if n >= 32 {
+			n %= 32             // Normally would be -= 32 but %= 32 informs compiler 0 <= n <= 31 for upcoming shift
+			y := uint32(x >> n) // Compiler doesn't combine memory writes if y isn't uint32
+			dst = append(dst, byte(y>>24), byte(y>>16), byte(y>>8), byte(y))
+		}
+	}
+	// Add padding bits if necessary
+	if over := n % 8; over > 0 {
+		const (
+			eosCode    = 0x3fffffff
+			eosNBits   = 30
+			eosPadByte = eosCode >> (eosNBits - 8)
+		)
+		pad := 8 - over
+		x = (x << pad) | (eosPadByte >> over)
+		n += pad // 8 now divides into n exactly
+	}
+	// n in (0, 8, 16, 24, 32)
+	switch n / 8 {
+	case 0:
+		return dst
+	case 1:
+		return append(dst, byte(x))
+	case 2:
+		y := uint16(x)
+		return append(dst, byte(y>>8), byte(y))
+	case 3:
+		y := uint16(x >> 8)
+		return append(dst, byte(y>>8), byte(y), byte(x))
+	}
+	//	case 4:
+	y := uint32(x)
+	return append(dst, byte(y>>24), byte(y>>16), byte(y>>8), byte(y))
+}
+
+// HuffmanEncodeLength returns the number of bytes required to encode
+// s in Huffman codes. The result is round up to byte boundary.
+func HuffmanEncodeLength(s string) uint64 {
+	n := uint64(0)
+	for i := 0; i < len(s); i++ {
+		n += uint64(huffmanCodeLen[s[i]])
+	}
+	return (n + 7) / 8
+}