chromium/net/third_party/quiche/src/quiche/http2/hpack/huffman/hpack_huffman_decoder.h

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef QUICHE_HTTP2_HPACK_HUFFMAN_HPACK_HUFFMAN_DECODER_H_
#define QUICHE_HTTP2_HPACK_HUFFMAN_HPACK_HUFFMAN_DECODER_H_

// HpackHuffmanDecoder is an incremental decoder of strings that have been
// encoded using the Huffman table defined in the HPACK spec.
// By incremental, we mean that the HpackHuffmanDecoder::Decode method does
// not require the entire string to be provided, and can instead decode the
// string as fragments of it become available (e.g. as HPACK block fragments
// are received for decoding by HpackEntryDecoder).

#include <stddef.h>

#include <cstdint>
#include <iosfwd>
#include <string>

#include "absl/strings/string_view.h"
#include "quiche/common/platform/api/quiche_export.h"

namespace http2 {

// HuffmanAccumulator is used to store bits during decoding, e.g. next N bits
// that have not yet been decoded, but have been extracted from the encoded
// string).  An advantage of using a uint64 for the accumulator
// is that it has room for the bits of the longest code plus the bits of a full
// byte; that means that when adding more bits to the accumulator, it can always
// be done in whole bytes. For example, if we currently have 26 bits in the
// accumulator, and need more to decode the current symbol, we can add a whole
// byte to the accumulator, and not have to do juggling with adding 6 bits (to
// reach 30), and then keep track of the last two bits we've not been able to
// add to the accumulator.
HuffmanAccumulator;
HuffmanAccumulatorBitCount;

// HuffmanBitBuffer stores the leading edge of bits to be decoded. The high
// order bit of accumulator_ is the next bit to be decoded.
class QUICHE_EXPORT HuffmanBitBuffer { … };

inline std::ostream& operator<<(std::ostream& out, const HuffmanBitBuffer& v) { … }

class QUICHE_EXPORT HpackHuffmanDecoder { … };

inline std::ostream& operator<<(std::ostream& out,
                                const HpackHuffmanDecoder& v) { … }

}  // namespace http2

#endif  // QUICHE_HTTP2_HPACK_HUFFMAN_HPACK_HUFFMAN_DECODER_H_