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// Copyright 2014 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_SPDY_CORE_HPACK_HPACK_HUFFMAN_TABLE_H_
#define QUICHE_SPDY_CORE_HPACK_HPACK_HUFFMAN_TABLE_H_
#include <cstddef>
#include <cstdint>
#include <vector>
#include "absl/strings/string_view.h"
#include "common/platform/api/quiche_export.h"
#include "spdy/core/hpack/hpack_constants.h"
namespace spdy {
namespace test {
class HpackHuffmanTablePeer;
} // namespace test
class HpackOutputStream;
// HpackHuffmanTable encodes string literals using a constructed canonical
// Huffman code. Once initialized, an instance is read only and may be accessed
// only through its const interface.
class QUICHE_EXPORT_PRIVATE HpackHuffmanTable {
public:
friend class test::HpackHuffmanTablePeer;
typedef HpackHuffmanSymbol Symbol;
HpackHuffmanTable();
~HpackHuffmanTable();
// Prepares HpackHuffmanTable to encode the canonical Huffman code as
// determined by the given symbols. Must be called exactly once.
// Returns false if the input symbols define an invalid coding, and true
// otherwise. Symbols must be presented in ascending ID order with no gaps,
// and |symbol_count| must fit in a uint16_t.
bool Initialize(const Symbol* input_symbols, size_t symbol_count);
// Returns whether Initialize() has been successfully called.
bool IsInitialized() const;
// Encodes the input string to the output stream using the table's Huffman
// context.
void EncodeString(absl::string_view in, HpackOutputStream* out) const;
// Returns the encoded size of the input string.
size_t EncodedSize(absl::string_view in) const;
// Returns the estimate of dynamically allocated memory in bytes.
size_t EstimateMemoryUsage() const;
private:
// Expects symbols ordered on ID ascending.
void BuildEncodeTable(const std::vector<Symbol>& symbols);
// Symbol code and code length, in ascending symbol ID order.
// Codes are stored in the most-significant bits of the word.
std::vector<uint32_t> code_by_id_;
std::vector<uint8_t> length_by_id_;
// The first 8 bits of the longest code. Applied when generating padding bits.
uint8_t pad_bits_;
// If initialization fails, preserve the symbol ID which failed validation
// for examination in tests.
uint16_t failed_symbol_id_;
};
} // namespace spdy
#endif // QUICHE_SPDY_CORE_HPACK_HPACK_HUFFMAN_TABLE_H_