// Copyright (C) 2016 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:data-parser

#ifndef QBYTEDATABUFFER_P_H

#define QBYTEDATABUFFER_P_H

//

//  W A R N I N G

//  -------------

//

// This file is not part of the Qt API.  It exists purely as an

// implementation detail.  This header file may change from version to

// version without notice, or even be removed.

//

// We mean it.

//

#include <QtNetwork/private/qtnetworkglobal_p.h>

#include <QtCore/qbytearray.h>

#include <QtCore/qlist.h>

#include <climits>

QT_BEGIN_NAMESPACE

// this class handles a list of QByteArrays. It is a variant of QRingBuffer

// that avoid malloc/realloc/memcpy.

class QByteDataBuffer

{

private:

    QList<QByteArray> buffers;

    qint64 bufferCompleteSize = 0;

    qint64 firstPos = 0;

public:

    static inline void popFront(QByteArray &ba, qint64 n)

    {

        ba = QByteArray(ba.constData() + n, ba.size() - n);

    }

    inline void squeezeFirst()

    {

        if (!buffers.isEmpty() && firstPos > 0) {

            popFront(buffers.first(), firstPos);

            firstPos = 0;

        }

    }

    inline void append(const QByteDataBuffer& other)

    {

        if (other.isEmpty())

            return;

        buffers.append(other.buffers);

        bufferCompleteSize += other.byteAmount();

        if (other.firstPos > 0)

            popFront(buffers[bufferCount() - other.bufferCount()], other.firstPos);

    }

    inline void append(QByteDataBuffer &&other)

    {

        if (other.isEmpty())

            return;

        auto otherBufferCount = other.bufferCount();

        auto otherByteAmount = other.byteAmount();

        buffers.append(std::move(other.buffers));

        bufferCompleteSize += otherByteAmount;

        if (other.firstPos > 0)

            popFront(buffers[bufferCount() - otherBufferCount], other.firstPos);

    }

    inline void append(const QByteArray& bd)

    {

        append(QByteArray(bd));

    }

    inline void append(QByteArray &&bd)

    {

        if (bd.isEmpty())

            return;

        bufferCompleteSize += bd.size();

        buffers.append(std::move(bd));

    }

    inline void prepend(const QByteArray& bd)

    {

        prepend(QByteArray(bd));

    }

    inline void prepend(QByteArray &&bd)

    {

        if (bd.isEmpty())

            return;

        squeezeFirst();

        bufferCompleteSize += bd.size();

        buffers.prepend(std::move(bd));

    }

    // return the first QByteData. User of this function has to free() its .data!

    // preferably use this function to read data.

    inline QByteArray read()

    {

        Q_ASSERT(!isEmpty());

        squeezeFirst();

        bufferCompleteSize -= buffers.first().size();

        return buffers.takeFirst();

    }

    // return everything. User of this function has to free() its .data!

    // avoid to use this, it might malloc and memcpy.

    inline QByteArray readAll()

    {

        return read(byteAmount());

    }

    // return amount. User of this function has to free() its .data!

    // avoid to use this, it might malloc and memcpy.

    inline QByteArray read(qint64 amount)

    {

        amount = qMin(byteAmount(), amount);

        if constexpr (sizeof(qsizetype) == sizeof(int)) { // 32-bit

            // While we cannot overall have more than INT_MAX memory allocated,

            // the QByteArrays we hold may be shared copies of each other,

            // causing byteAmount() to exceed INT_MAX.

            if (amount > INT_MAX)

                qBadAlloc(); // what resize() would do if it saw past the truncation

        }

        QByteArray byteData;

        byteData.resize(qsizetype(amount));

        read(byteData.data(), byteData.size());

        return byteData;

    }

    // return amount bytes. User of this function has to free() its .data!

    // avoid to use this, it will memcpy.

    qint64 read(char* dst, qint64 amount)

    {

        amount = qMin(amount, byteAmount());

        qint64 originalAmount = amount;

        char *writeDst = dst;

        while (amount > 0) {

            const QByteArray &first = buffers.first();

            qint64 firstSize = first.size() - firstPos;

            if (amount >= firstSize) {

                // take it completely

                bufferCompleteSize -= firstSize;

                amount -= firstSize;

                memcpy(writeDst, first.constData() + firstPos, firstSize);

                writeDst += firstSize;

                firstPos = 0;

                buffers.takeFirst();

            } else {

                // take a part of it & it is the last one to take

                bufferCompleteSize -= amount;

                memcpy(writeDst, first.constData() + firstPos, amount);

                firstPos += amount;

                amount = 0;

            }

        }

        return originalAmount;

    }

    /*!

        \internal

        Returns a view into the first QByteArray contained inside,

        ignoring any already read data. Call advanceReadPointer()

        to advance the view forward. When a QByteArray is exhausted

        the view returned by this function will view into another

        QByteArray if any. Returns a default constructed view if

        no data is available.

        \sa advanceReadPointer

    */

    QByteArrayView readPointer() const

    {

        if (isEmpty())

            return {};

        return { buffers.first().constData() + qsizetype(firstPos),

                 buffers.first().size() - qsizetype(firstPos) };

    }

    /*!

        \internal

        Advances the read pointer by \a distance.

        \sa readPointer

    */

    void advanceReadPointer(qint64 distance)

    {

        qint64 newPos = firstPos + distance;

        if (isEmpty()) {

            newPos = 0;

        } else if (auto size = buffers.first().size(); newPos >= size) {

            while (newPos >= size) {

                bufferCompleteSize -= (size - firstPos);

                newPos -= size;

                buffers.pop_front();

                if (isEmpty()) {

                    size = 0;

                    newPos = 0;

                    break;

                }

                size = buffers.front().size();

            }

            bufferCompleteSize -= newPos;

        } else {

            bufferCompleteSize -= newPos - firstPos;

        }

        firstPos = newPos;

    }

    inline char getChar()

    {

        Q_ASSERT_X(!isEmpty(), "QByteDataBuffer::getChar",

                   "Cannot read a char from an empty buffer!");

        char c;

        read(&c, 1);

        return c;

    }

    inline void clear()

    {

        buffers.clear();

        bufferCompleteSize = 0;

        firstPos = 0;

    }

    // The byte count of all QByteArrays

    inline qint64 byteAmount() const

    {

        return bufferCompleteSize;

    }

    // the number of QByteArrays

    qsizetype bufferCount() const

    {

        return buffers.size();

    }

    inline bool isEmpty() const

    {

        return byteAmount() == 0;

    }

    inline qint64 sizeNextBlock() const

    {

        if (buffers.isEmpty())

            return 0;

        else

            return buffers.first().size() - firstPos;

    }

    QByteArray &operator[](qsizetype i)

    {

        if (i == 0)

            squeezeFirst();

        return buffers[i];

    }

    inline bool canReadLine() const {

        qsizetype i = 0;

        if (i < buffers.size()) {

            if (buffers.at(i).indexOf('\n', firstPos) != -1)

                return true;

            ++i;

            for (; i < buffers.size(); i++)

                if (buffers.at(i).contains('\n'))

                    return true;

        }

        return false;

    }

    const QByteArray &last() const { return buffers.last(); }

};

QT_END_NAMESPACE

#endif // QBYTEDATABUFFER_P_H