summaryrefslogtreecommitdiffstats
path: root/src/network/access/http2/huffman_p.h
blob: c5324d42b1998fdd442a0843d731c09bb709bae2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtNetwork module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

#ifndef HUFFMAN_P_H
#define HUFFMAN_P_H

//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists for the convenience
// of other Qt classes.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//

#include <QtCore/qglobal.h>

QT_BEGIN_NAMESPACE

class QByteArray;

namespace HPack
{

struct CodeEntry
{
    quint32 byteValue;
    quint32 huffmanCode;
    quint32 bitLength;
};

class BitOStream;

quint64 huffman_encoded_bit_length(const QByteArray &inputData);
void huffman_encode_string(const QByteArray &inputData, BitOStream &outputStream);

// PrefixTable:
// Huffman codes with a small bit length
// fit into a table (these are 'terminal' symbols),
// codes with longer codes require additional
// tables, so several symbols will have the same index
// in a table - pointing into the next table.
// Every table has an 'indexLength' - that's
// how many bits can fit in table's indices +
// 'prefixLength' - how many bits were addressed
// by its 'parent' table(s).
// All PrefixTables are kept in 'prefixTables' array.
// PrefixTable itself does not have any entries,
// it just holds table's prefix/index + 'offset' -
// there table's data starts in an array of all
// possible entries ('tableData').

struct PrefixTable
{
    PrefixTable()
        : prefixLength(),
          indexLength(),
          offset()
    {
    }

    PrefixTable(quint32 prefix, quint32 index)
        : prefixLength(prefix),
          indexLength(index),
          offset()
    {
    }

    quint32 size()const
    {
        // Number of entries table contains:
        return 1 << indexLength;
    }

    quint32 prefixLength;
    quint32 indexLength;
    quint32 offset;
};

// Table entry is either a terminal entry (thus probably the code found)
// or points into another table ('nextTable' - index into
// 'prefixTables' array). If it's a terminal, 'nextTable' index
// refers to the same table.

struct PrefixTableEntry
{
    PrefixTableEntry()
        : bitLength(),
          nextTable(),
          byteValue()
    {
    }

    quint32 bitLength;
    quint32 nextTable;
    quint32 byteValue;
};

class BitIStream;

class HuffmanDecoder
{
public:
    enum class BitConstants
    {
        rootPrefix = 9,
        childPrefix = 6
    };

    HuffmanDecoder();

    bool decodeStream(BitIStream &inputStream, QByteArray &outputBuffer);

private:
    quint32 addTable(quint32 prefixLength, quint32 indexLength);
    PrefixTableEntry tableEntry(const PrefixTable &table, quint32 index);
    void setTableEntry(const PrefixTable &table, quint32 index, const PrefixTableEntry &entry);

    std::vector<PrefixTable> prefixTables;
    std::vector<PrefixTableEntry> tableData;
    quint32 minCodeLength;
};

bool huffman_decode_string(BitIStream &inputStream, QByteArray *outputBuffer);

} // namespace HPack

QT_END_NAMESPACE

#endif