stringutil.cpp

Go to the documentation of this file.

#include <array>
#include <bit>
#include <QObject>
#include "stringutil.h"
 
// For the spaceship operator, the c++ standard library explicitly
// requires '0' and not nullptr.  NOLINTBEGIN(modernize-use-nullptr)
 
bool StringUtil::isValidUTF8(const QByteArray& data)
{
    const auto* p = (const unsigned char*)data.data();
    const unsigned char* const end = p + data.size();
    while (p < end)
    {
        int code_point_length = std::countl_one(*p);
 
        switch (code_point_length)
        {
        case 0: p++; continue; // ASCII
        case 1: return false;  // invalid, continuation byte
        case 2:
        case 3:
        case 4: break;
        default: return false;
        /* the variable length code is limited to 4 bytes by RFC3629 §3 to match
           the range of UTF-16, i.e. the maximum code point is U+10FFFF
        */
        }
 
        if (end < code_point_length + p)
        {
            return false; // truncated codepoint at end
        }
 
        // verify each starting byte is followed by the correct number of continuation bytes
        switch (code_point_length)
        {
        case 4:
            if (std::countl_one(p[3]) != 1)
            {
                return false;
            }
            [[fallthrough]];
        case 3:
            if (std::countl_one(p[2]) != 1)
            {
                return false;
            }
            [[fallthrough]];
        case 2:
            if (std::countl_one(p[1]) != 1)
            {
                return false;
            }
            break;
        default: break; // should never be reached
        }
 
        // all continuation bytes are in the range 0x80 to 0xBF
        switch (code_point_length)
        {
        case 2:
            // overlong encoding of single byte character
            if (*p == 0xC0 || *p == 0xC1)
            {
                return false;
            }
            break;
        case 3:
            // U+D800–U+DFFF are invalid; UTF-16 surrogate halves
            // 0xED'A0'80 to 0xED'BF'BF
            if (p[0] == 0xED && p[1] >= 0xA0)
            {
                return false;
            }
            // overlong encoding of 2 byte character
            if (p[0] == 0xE0 && p[1] < 0xA0)
            {
                return false;
            }
            break;
        case 4:
            // code points > U+10FFFF are invalid
            // U+10FFFF in UTF-8 is 0xF4'8F'BF'BF
            // U+110000 in UTF-8 is 0xF4'90'80'80
            if (*p > 0xF4 || (p[0] == 0xF4 && p[1] >= 0x90))
            {
                return false;
            }
            // overlong encoding of 3 byte character
            if (p[0] == 0xF0 && p[1] < 0x90)
            {
                return false;
            }
            break;
        default: break; // should never be reached
        }
 
        p += code_point_length;
    }
 
    return true;
}
 
std::strong_ordering StringUtil::naturalCompare(const QString &_a, const QString &_b, Qt::CaseSensitivity caseSensitivity)
{
    QString a;
    QString b;
 
    if (caseSensitivity == Qt::CaseSensitive)
    {
        a = _a;
        b = _b;
    }
    else
    {
        a = _a.toLower();
        b = _b.toLower();
    }
 
    const QChar* currA = a.unicode(); // iterator over a
    const QChar* currB = b.unicode(); // iterator over b
 
    if (currA == currB)
    {
        return std::strong_ordering::equal;
    }
 
    while (!currA->isNull() && !currB->isNull())
    {
        const QChar* begSeqA = currA; // beginning of a new character sequence of a
        const QChar* begSeqB = currB;
 
        if (currA->unicode() == QChar::ObjectReplacementCharacter)
            return std::strong_ordering::greater;
        if (currB->unicode() == QChar::ObjectReplacementCharacter)
            return std::strong_ordering::less;
 
        if (currA->unicode() == QChar::ReplacementCharacter)
            return std::strong_ordering::greater;
        if (currB->unicode() == QChar::ReplacementCharacter)
            return std::strong_ordering::less;
 
        // find sequence of characters ending at the first non-character
        while (!currA->isNull() && !currA->isDigit() && !currA->isPunct() &&
               !currA->isSpace())
        {
            ++currA;
        }
 
        while (!currB->isNull() && !currB->isDigit() && !currB->isPunct() &&
               !currB->isSpace())
        {
            ++currB;
        }
 
        // compare these sequences
        const QString& subA(a.mid(begSeqA - a.unicode(), currA - begSeqA));
        const QString& subB(b.mid(begSeqB - b.unicode(), currB - begSeqB));
        int cmp = QString::localeAwareCompare(subA, subB);
        if (cmp != 0)
            return cmp < 0 ? std::strong_ordering::less : std::strong_ordering::greater;
 
        if (currA->isNull() || currB->isNull())
            break;
 
        // find sequence of characters ending at the first non-character
        while ((currA->isPunct() || currA->isSpace()) &&
               (currB->isPunct() || currB->isSpace()))
        {
            auto cmp2 = (currA->unicode() <=> currB->unicode());
            if (cmp2 != 0)
                return cmp2;
            ++currA;
            ++currB;
            if (currA->isNull() || currB->isNull())
            {
                break;
            }
        }
 
        // now some digits follow...
        if ((*currA == QLatin1Char('0')) || (*currB == QLatin1Char('0')))
        {
            // one digit-sequence starts with 0 -> assume we are in a fraction part
            // do left aligned comparison (numbers are considered left aligned)
            while (true)
            {
                if (!currA->isDigit() && !currB->isDigit())
                    break;
                if (!currA->isDigit())
                    return std::strong_ordering::greater;
                if (!currB->isDigit())
                    return std::strong_ordering::less;
                auto cmp2 = (currA->unicode() <=> currB->unicode());
                if (cmp2 != 0)
                    return cmp2;
                ++currA;
                ++currB;
            }
        }
        else
        {
            // No digit-sequence starts with 0 -> assume we are looking at some integer
            // do right aligned comparison.
            //
            // The longest run of digits wins. That aside, the greatest
            // value wins, but we can't know that it will until we've scanned
            // both numbers to know that they have the same magnitude.
 
            bool isFirstRun = true;
            std::strong_ordering weight = std::strong_ordering::equal;
 
            while (true)
            {
                if (!currA->isDigit() && !currB->isDigit())
                {
                    if (weight != 0)
                        return weight;
                    break;
                }
                if (!currA->isDigit())
                {
                    if (isFirstRun)
                        return currA->unicode() <=> currB->unicode();
                    return std::strong_ordering::less;
                }
                if (!currB->isDigit())
                {
                    if (isFirstRun)
                        return currA->unicode() <=> currB->unicode();
                    return std::strong_ordering::greater;
                }
                if (weight == 0)
                    weight = (currA->unicode() <=> currB->unicode());
                ++currA;
                ++currB;
                isFirstRun = false;
            }
        }
    }
 
    if (currA->isNull() && currB->isNull())
    {
        if (caseSensitivity == Qt::CaseSensitive)
            return std::strong_ordering::equal;
        return std::strong_ordering::equivalent;
    }
 
    return currA->isNull() ? std::strong_ordering::less : std::strong_ordering::greater;
}
 
static constexpr int64_t kOneTerabyte { 1024 * 1024LL * 1024};
static constexpr int64_t kOneGigabyte {        1024LL * 1024};
static constexpr int64_t kOneMegabyte {                 1024};
 
QString StringUtil::formatKBytes(int64_t sizeKB, int precision)
{
    if (sizeKB > kOneTerabyte)
    {
        double sizeTB = sizeKB/(1.0 * kOneTerabyte);
        return QObject::tr("%1 TB").arg(sizeTB, 0, 'f', (sizeTB>10)?0:precision);
    }
    if (sizeKB > kOneGigabyte)
    {
        double sizeGB = sizeKB/(1.0 * kOneGigabyte);
        return QObject::tr("%1 GB").arg(sizeGB, 0, 'f', (sizeGB>10)?0:precision);
    }
    if (sizeKB > kOneMegabyte)
    {
        double sizeMB = sizeKB/(1.0 * kOneMegabyte);
        return QObject::tr("%1 MB").arg(sizeMB, 0, 'f', (sizeMB>10)?0:precision);
    }
    // Kilobytes
    return QObject::tr("%1 KB").arg(sizeKB);
}
 
QString StringUtil::formatBytes(int64_t sizeB, int precision)
{
    if (sizeB > 1024)
        return formatKBytes(sizeB / 1024, precision);
    return QString("%1 B").arg(sizeB);
}
 
// NOLINTEND(modernize-use-nullptr)