qt-everywhere-src-5.15.1/qtbase/src/corelib/text/qbytearraymatcher.h

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#ifndef QBYTEARRAYMATCHER_H
#define QBYTEARRAYMATCHER_H

#include <QtCore/qbytearray.h>

QT_BEGIN_NAMESPACE


class QByteArrayMatcherPrivate;

class Q_CORE_EXPORT QByteArrayMatcher
{
public:
    QByteArrayMatcher();
    explicit QByteArrayMatcher(const QByteArray &pattern);
    explicit QByteArrayMatcher(const char *pattern, int length);
    QByteArrayMatcher(const QByteArrayMatcher &other);
    ~QByteArrayMatcher();

    QByteArrayMatcher &operator=(const QByteArrayMatcher &other);

    void setPattern(const QByteArray &pattern);

    int indexIn(const QByteArray &ba, int from = 0) const;
    int indexIn(const char *str, int len, int from = 0) const;
    inline QByteArray pattern() const
    {
        if (q_pattern.isNull())
            return QByteArray(reinterpret_cast<const char*>(p.p), p.l);
        return q_pattern;
    }

private:
    QByteArrayMatcherPrivate *d;
    QByteArray q_pattern;
    struct Data {
        uchar q_skiptable[256];
        const uchar *p;
        int l;
    };
    union {
        uint dummy[256];
        Data p;
    };
};

class QStaticByteArrayMatcherBase
{
    Q_DECL_ALIGN(16)
    struct Skiptable {
        uchar data[256];
    } m_skiptable;
protected:
    explicit Q_DECL_RELAXED_CONSTEXPR QStaticByteArrayMatcherBase(const char *pattern, uint n) noexcept
        : m_skiptable(generate(pattern, n)) {}
    // compiler-generated copy/more ctors/assignment operators are ok!
    // compiler-generated dtor is ok!

    Q_CORE_EXPORT int indexOfIn(const char *needle, uint nlen, const char *haystack, int hlen, int from) const noexcept;

private:
    static Q_DECL_RELAXED_CONSTEXPR Skiptable generate(const char *pattern, uint n) noexcept
    {
        const auto uchar_max = (std::numeric_limits<uchar>::max)();
        uchar max = n > uchar_max ? uchar_max : n;
        Skiptable table = {
            // this verbose initialization code aims to avoid some opaque error messages
            // even on powerful compilers such as GCC 5.3. Even though for GCC a loop
            // format can be found that v5.3 groks, it's probably better to go with this
            // for the time being:
            {
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,

                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
                max, max, max, max, max, max, max, max,   max, max, max, max, max, max, max, max,
            }
        };
        pattern += n - max;
        while (max--)
            table.data[uchar(*pattern++)] = max;
        return table;
    }
};

template <uint N>
class QStaticByteArrayMatcher : QStaticByteArrayMatcherBase
{
    char m_pattern[N];
    Q_STATIC_ASSERT_X(N > 2, "QStaticByteArrayMatcher makes no sense for finding a single-char pattern");
public:
    explicit Q_DECL_RELAXED_CONSTEXPR QStaticByteArrayMatcher(const char (&patternToMatch)[N]) noexcept
        : QStaticByteArrayMatcherBase(patternToMatch, N - 1), m_pattern()
    {
        for (uint i = 0; i < N; ++i)
            m_pattern[i] = patternToMatch[i];
    }

    int indexIn(const QByteArray &haystack, int from = 0) const noexcept
    { return this->indexOfIn(m_pattern, N - 1, haystack.data(), haystack.size(), from); }
    int indexIn(const char *haystack, int hlen, int from = 0) const noexcept
    { return this->indexOfIn(m_pattern, N - 1, haystack, hlen, from); }

    QByteArray pattern() const { return QByteArray(m_pattern, int(N - 1)); }
};

template <uint N>
Q_DECL_RELAXED_CONSTEXPR QStaticByteArrayMatcher<N> qMakeStaticByteArrayMatcher(const char (&pattern)[N]) noexcept
{ return QStaticByteArrayMatcher<N>(pattern); }

QT_END_NAMESPACE

#endif // QBYTEARRAYMATCHER_H