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Fixes #113

Signed-off-by: Marcos Lilljedahl <marcosnils@gmail.com>

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

@@ -0,0 +1,190 @@
+// 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 {
+	n := rootHuffmanNode
+	cur, nbits := uint(0), uint8(0)
+	for _, b := range v {
+		cur = cur<<8 | uint(b)
+		nbits += 8
+		for nbits >= 8 {
+			idx := byte(cur >> (nbits - 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)
+				nbits -= n.codeLen
+				n = rootHuffmanNode
+			} else {
+				nbits -= 8
+			}
+		}
+	}
+	for nbits > 0 {
+		n = n.children[byte(cur<<(8-nbits))]
+		if n.children != nil || n.codeLen > nbits {
+			break
+		}
+		buf.WriteByte(n.sym)
+		nbits -= n.codeLen
+		n = rootHuffmanNode
+	}
+	return nil
+}
+
+type node struct {
+	// children is non-nil for internal nodes
+	children []*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: make([]*node, 256)}
+}
+
+var rootHuffmanNode = newInternalNode()
+
+func init() {
+	if len(huffmanCodes) != 256 {
+		panic("unexpected size")
+	}
+	for i, code := range huffmanCodes {
+		addDecoderNode(byte(i), code, huffmanCodeLen[i])
+	}
+}
+
+func addDecoderNode(sym byte, code uint32, codeLen uint8) {
+	cur := rootHuffmanNode
+	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)
+	for i := start; i < start+end; i++ {
+		cur.children[i] = &node{sym: sym, codeLen: codeLen}
+	}
+}
+
+// AppendHuffmanString appends s, as encoded in Huffman codes, to dst
+// and returns the extended buffer.
+func AppendHuffmanString(dst []byte, s string) []byte {
+	rembits := uint8(8)
+
+	for i := 0; i < len(s); i++ {
+		if rembits == 8 {
+			dst = append(dst, 0)
+		}
+		dst, rembits = appendByteToHuffmanCode(dst, rembits, s[i])
+	}
+
+	if rembits < 8 {
+		// special EOS symbol
+		code := uint32(0x3fffffff)
+		nbits := uint8(30)
+
+		t := uint8(code >> (nbits - rembits))
+		dst[len(dst)-1] |= t
+	}
+
+	return dst
+}
+
+// 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
+}
+
+// appendByteToHuffmanCode appends Huffman code for c to dst and
+// returns the extended buffer and the remaining bits in the last
+// element. The appending is not byte aligned and the remaining bits
+// in the last element of dst is given in rembits.
+func appendByteToHuffmanCode(dst []byte, rembits uint8, c byte) ([]byte, uint8) {
+	code := huffmanCodes[c]
+	nbits := huffmanCodeLen[c]
+
+	for {
+		if rembits > nbits {
+			t := uint8(code << (rembits - nbits))
+			dst[len(dst)-1] |= t
+			rembits -= nbits
+			break
+		}
+
+		t := uint8(code >> (nbits - rembits))
+		dst[len(dst)-1] |= t
+
+		nbits -= rembits
+		rembits = 8
+
+		if nbits == 0 {
+			break
+		}
+
+		dst = append(dst, 0)
+	}
+
+	return dst, rembits
+}