bitstreams_p.h - mozsearch

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// Copyright (C) 2018 The Qt Company Ltd.

// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

// Qt-Security score:critical reason:network-protocol

#ifndef BITSTREAMS_P_H

#define BITSTREAMS_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/private/qtcoreglobal_p.h>

#include <QtCore/qassert.h>

#include <QtCore/qtclasshelpermacros.h>

#include <QtCore/qtypes.h>

#include <type_traits>

#include <algorithm>

#include <vector>

QT_BEGIN_NAMESPACE

class QByteArray;

class QByteArrayView;

namespace HPack

// BitOStream works with an external buffer,

// for example, HEADERS frame.

class Q_AUTOTEST_EXPORT BitOStream

public:

    BitOStream(std::vector<uchar> &buffer);

    // Write 'bitLength' bits from the least significant

    // bits in 'bits' to bitstream:

    void writeBits(uchar bits, quint8 bitLength);

    // HPACK data format, we support:

    // * 32-bit integers

    // * strings

    void write(quint32 src);

    void write(QByteArrayView src, bool compressed);

    quint64 bitLength() const;

    quint64 byteLength() const;

    const uchar *begin() const;

    const uchar *end() const;

    void clear();

private:

    Q_DISABLE_COPY_MOVE(BitOStream);

    std::vector<uchar> &buffer;

    quint64 bitsSet;

};

class Q_AUTOTEST_EXPORT BitIStream

public:

    // Error is set by 'read' functions.

    // 'peek' does not set the error,

    // since it just peeks some bits

    // without the notion of wrong/right.

    // 'read' functions only change 'streamOffset'

    // on success.

    enum class Error

        NoError,

        NotEnoughData,

        CompressionError,

        InvalidInteger

};

    BitIStream();

    BitIStream(const uchar *f, const uchar *l);

    quint64 bitLength() const;

    bool hasMoreBits() const;

    // peekBits tries to read 'length' bits from the bitstream into

    // 'dst' ('length' must be <= sizeof(dst) * 8), packing them

    // starting from the most significant bit of the most significant

    // byte. It's a template so that we can use it with different

    // integer types. Returns the number of bits actually read.

    // Does not change stream's offset.

    template<class T>

    quint64 peekBits(quint64 from, quint64 length, T *dstPtr) const

        static_assert(std::is_unsigned<T>::value, "peekBits: unsigned integer type expected");

        Q_ASSERT(dstPtr);

        Q_ASSERT(length <= sizeof(T) * 8);

        if (from >= bitLength() || !length)

            return 0;

        T &dst = *dstPtr;

        dst = T();

        length = std::min(length, bitLength() - from);

        const uchar *srcByte = first + from / 8;

        auto bitsToRead = length + from % 8;

        while (bitsToRead > 8) {

            dst = (dst << 8) | *srcByte;

            bitsToRead -= 8;

            ++srcByte;

        dst <<= bitsToRead;

        dst |= *srcByte >> (8 - bitsToRead);

        dst <<= sizeof(T) * 8 - length;

        return length;

    quint64 streamOffset() const

        return offset;

    bool skipBits(quint64 nBits);

    bool rewindOffset(quint64 nBits);

    bool read(quint32 *dstPtr);

    bool read(QByteArray *dstPtr);

    Error error() const;

private:

    void setError(Error newState);

    const uchar *first;

    const uchar *last;

    quint64 offset;

    Error streamError;

};

} // namespace HPack

QT_END_NAMESPACE

#endif