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****************************************************************************/

#include <QString>

#include "qcompressedwhitespace_p.h"

QT_BEGIN_NAMESPACE

using namespace QPatternist;

CompressedWhitespace::CharIdentifier CompressedWhitespace::toIdentifier(const QChar ch)

{

    switch(ch.unicode())

    {

        case ' ':

            return Space;

        case '\n':

            return LF;

        case '\r':

            return CR;

        case '\t':

            return Tab;

        default:

        {

            Q_ASSERT_X(false, Q_FUNC_INFO,

                       "The caller must guarantee only whitespace is passed.");

            return Tab;

        }

    }

}

bool CompressedWhitespace::isEven(const int number)

{

    Q_ASSERT(number >= 0);

    return number % 2 == 0;

}

quint8 CompressedWhitespace::toCompressedChar(const QChar ch, const int len)

{

    Q_ASSERT(len > 0);

    Q_ASSERT(len <= MaxCharCount);

    return len + toIdentifier(ch);

}

QChar CompressedWhitespace::toChar(const CharIdentifier id)

{

    switch(id)

    {

        case Space: return QLatin1Char(' ');

        case CR:    return QLatin1Char('\r');

        case LF:    return QLatin1Char('\n');

        case Tab:   return QLatin1Char('\t');

        default:

                    {

                        Q_ASSERT_X(false, Q_FUNC_INFO, "Unexpected input");

                        return QChar();

                    }

    }

}

QString CompressedWhitespace::compress(const QStringRef &input)

{

    Q_ASSERT(!isEven(1) && isEven(0) && isEven(2));

    Q_ASSERT(!input.isEmpty());

    QString result;

    const int len = input.length();

    /* The amount of compressed characters. For instance, if input is

     * four spaces followed by one tab, compressedChars will be 2, and the resulting

     * QString will have a length of 1, two compressedChars stored in one QChar. */

    int compressedChars = 0;

    for(int i = 0; i < len; ++i)

    {

        const QChar c(input.at(i));

        int start = i;

        while(true)

        {

            if(i + 1 == input.length() || input.at(i + 1) != c)

                break;

            else

                ++i;

        }

        /* The length of subsequent whitespace characters in the input. */

        int wsLen = (i - start) + 1;

        /* We might get a sequence of whitespace that is so long, that we can't

         * store it in one unit/byte. In that case we chop it into as many subsequent

         * ones that is needed. */

        while(true)

        {

            const int unitLength = qMin(wsLen, int(MaxCharCount));

            wsLen -= unitLength;

            ushort resultCP = toCompressedChar(c, unitLength);

            if(isEven(compressedChars))

                result += QChar(resultCP);

            else

            {

                resultCP = resultCP << 8;

                resultCP |= result.at(result.size() - 1).unicode();

                result[result.size() - 1] = resultCP;

            }

            ++compressedChars;

            if(wsLen == 0)

                break;

        }

    }

    return result;

}

QString CompressedWhitespace::decompress(const QString &input)

{

    Q_ASSERT(!input.isEmpty());

    const int len = input.length() * 2;

    QString retval;

    for(int i = 0; i < len; ++i)

    {

        ushort cp = input.at(i / 2).unicode();

        if(isEven(i))

            cp &= Lower8Bits;

        else

        {

            cp = cp >> 8;

            if(cp == 0)

                return retval;

        }

        const quint8 wsLen = cp & Lower6Bits;

        const quint8 id = cp & UpperTwoBits;

        /* Resize retval, and fill in on the top. */

        const int oldSize = retval.size();

        const int newSize = retval.size() + wsLen;

        retval.resize(newSize);

        const QChar ch(toChar(CharIdentifier(id)));

        for(int f = oldSize; f < newSize; ++f)

            retval[f] = ch;

    }

    return retval;

}

QT_END_NAMESPACE