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 ** Copyright (C) 2020-2022 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
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 #include "qstringtokenizer.h"
 #include "qstringalgorithms.h"
 
 /*!
     \class QStringTokenizer
     \brief The QStringTokenizer class splits strings into tokens along given separators
     \reentrant
 
     Splits a string into substrings wherever a given separator occurs,
     and returns a (lazy) list of those strings. If the separator does
     not match anywhere in the string, produces a single-element
     containing this string.  If the separator is empty,
     QStringTokenizer produces an empty string, followed by each of the
     string's characters, followed by another empty string. The two
     enumerations Qt::SplitBehavior and Qt::CaseSensitivity further
     control the output.
 
     QStringTokenizer drives QStringView::tokenize(), but, at least with a
     recent compiler, you can use it directly, too:
 
     \code
     for (auto it : QStringTokenizer{string, separator})
         use(*it);
     \endcode
 
     \note You should never, ever, name the template arguments of a
     QStringTokenizer explicitly.  If you can use C++17 Class Template
     Argument Deduction (CTAD), you may write
     \c{QStringTokenizer{string, separator}} (without template
     arguments).  If you can't use C++17 CTAD, you must use the
     QStringView::split() or QLatin1String::split() member functions
     and store the return value only in \c{auto} variables:
 
     \code
     auto result = string.split(sep);
     \endcode
 
     This is because the template arguments of QStringTokenizer have a
     very subtle dependency on the specific string and separator types
     from with which they are constructed, and they don't usually
     correspond to the actual types passed.
 
     \section Lazy Sequences
 
     QStringTokenizer acts as a so-called lazy sequence, that is, each
     next element is only computed once you ask for it. Lazy sequences
     have the advantage that they only require O(1) memory. They have
     the disadvantage that, at least for QStringTokenizer, they only
     allow forward, not random-access, iteration.
 
     The intended use-case is that you just plug it into a ranged for loop:
 
     \code
     for (auto it : QStringTokenizer{string, separator})
         use(*it);
     \endcode
 
     or a C++20 ranged algorithm:
 
     \code
     std::ranges::for_each(QStringTokenizer{string, separator},
                           [] (auto token) { use(token); });
     \endcode
 
     \section End Sentinel
 
     The QStringTokenizer iterators cannot be used with classical STL
     algorithms, because those require iterator/iterator pairs, while
     QStringTokenizer uses sentinels, that is, it uses a different
     type, QStringTokenizer::sentinel, to mark the end of the
     range. This improves performance, because the sentinel is an empty
     type. Sentinels are supported from C++17 (for ranged for)
     and C++20 (for algorithms using the new ranges library).
 
     QStringTokenizer falls back to a non-sentinel end iterator
     implementation if the compiler doesn't support separate types for
     begin and end iterators in ranged for loops
     (\link{https://wg21.link/P0184}{P1084}), in which case traditional
     STL algorthms will \em appear to be supported, but as you migrate
     to a compiler that supports P0184, such code will break.  We
     recommend to use only the C++20 \c{std::ranges} algorithms, or, if
     you're stuck on C++14/17 for the time being,
     \link{https://github.com/ericniebler/range-v3}{Eric Niebler's
     Ranges v3 library}, which has the same semantics as the C++20
     \c{std::ranges} library.
 
     \section Temporaries
 
     QStringTokenizer is very carefully designed to avoid dangling
     references. If you construct a tokenizer from a temporary string
     (an rvalue), that argument is stored internally, so the referenced
     data isn't deleted before it is tokenized:
 
     \code
     auto tok = QStringTokenizer{widget.text(), u','};
     // return value of `widget.text()` is destroyed, but content was moved into `tok`
     for (auto e : tok)
        use(e);
     \endcode
 
     If you pass named objects (lvalues), then QStringTokenizer does
     not store a copy. You are reponsible to keep the named object's
     data around for longer than the tokenizer operates on it:
 
     \code
     auto text = widget.text();
     auto tok = QStringTokenizer{text, u','};
     text.clear();      // destroy content of `text`
     for (auto e : tok) // ERROR: `tok` references deleted data!
         use(e);
     \endcode
 
     \sa QStringView::split(), QLatin1Sting::split(), Qt::SplitBehavior, Qt::CaseSensitivity
 */
 
 /*!
     \typedef QStringTokenizer::value_type
 
     Alias for \c{const QStringView} or \c{const QLatin1String},
     depending on the tokenizer's \c Haystack template argument.
 */
 
 /*!
     \typedef QStringTokenizer::difference_type
 
     Alias for qsizetype.
 */
 
 /*!
     \typedef QStringTokenizer::size_type
 
     Alias for qsizetype.
 */
 
 /*!
     \typedef QStringTokenizer::reference
 
     Alias for \c{value_type &}.
 
     QStringTokenizer does not support mutable references, so this is
     the same as const_reference.
 */
 
 /*!
     \typedef QStringTokenizer::const_reference
 
     Alias for \c{value_type &}.
 */
 
 /*!
     \typedef QStringTokenizer::pointer
 
     Alias for \c{value_type *}.
 
     QStringTokenizer does not support mutable iterators, so this is
     the same as const_pointer.
 */
 
 /*!
     \typedef QStringTokenizer::const_pointer
 
     Alias for \c{value_type *}.
 */
 
 /*!
     \typedef QStringTokenizer::iterator
 
     This typedef provides an STL-style const iterator for
     QStringTokenizer.
 
     QStringTokenizer does not support mutable iterators, so this is
     the same as const_iterator.
 
     \sa const_iterator
 */
 
 /*!
     \typedef QStringTokenizer::const_iterator
 
     This typedef provides an STL-style const iterator for
     QStringTokenizer.
 
     \sa iterator
 */
 
 /*!
     \typedef QStringTokenizer::sentinel
 
     This typedef provides an STL-style sentinel for
     QStringTokenizer::iterator and QStringTokenizer::const_iterator.
 
     \sa const_iterator
 */
 
 /*!
     \fn QStringTokenizer(Haystack haystack, String needle, Qt::CaseSensitivity cs, Qt::SplitBehavior sb)
     \fn QStringTokenizer(Haystack haystack, String needle, Qt::SplitBehavior sb, Qt::CaseSensitivity cs)
 
     Constructs a string tokenizer that splits the string \a haystack
     into substrings wherever \a needle occurs, and allows iteration
     over those strings as they are found. If \a needle does not match
     anywhere in \a haystack, a single element containing \a haystack
     is produced.
 
     \a cs specifies whether \a needle should be matched case
     sensitively or case insensitively.
 
     If \a sb is QString::SkipEmptyParts, empty entries don't
     appear in the result. By default, empty entries are included.
 
     \sa QStringView::split(), QLatin1String::split(), Qt::CaseSensitivity, Qt::SplitBehavior
 */
 
 /*!
     \fn QStringTokenizer::const_iterator QStringTokenizer::begin() const
 
     Returns a const \l{STL-style iterators}{STL-style iterator}
     pointing to the first token in the list.
 
     \sa end(), cbegin()
 */
 
 /*!
     \fn QStringTokenizer::const_iterator QStringTokenizer::cbegin() const
 
     Same as begin().
 
     \sa cend(), begin()
 */
 
 /*!
     \fn QStringTokenizer::sentinel QStringTokenizer::end() const
 
     Returns a const \l{STL-style iterators}{STL-style sentinel}
     pointing to the imaginary token after the last token in the list.
 
     \sa begin(), cend()
 */
 
 /*!
     \fn QStringTokenizer::sentinel QStringTokenizer::cend() const
 
     Same as end().
 
     \sa cbegin(), end()
 */
 
 /*!
     \fn QStringTokenizer::toContainer(Container &&c) const &
 
     Convenience method to convert the lazy sequence into a
     (typically) random-access container.
 
     This function is only available if \c Container has a \c value_type
     matching this tokenizer's value_type.
 
     If you pass in a named container (an lvalue), then that container
     is filled, and a reference to it is returned.
 
     If you pass in a temporary container (an rvalue, incl. the default
     argument), then that container is filled, and returned by value.
 
     \code
     // assuming tok's value_type is QStringView, then...
     auto tok = QStringTokenizer{~~~};
     // ... rac1 is a QVector:
     auto rac1 = tok.toContainer();
     // ... rac2 is std::pmr::vector<QStringView>:
     auto rac2 = tok.toContainer<std::pmr::vector<QStringView>>();
     auto rac3 = QVarLengthArray<QStringView, 12>{};
     // appends the token sequence produced by tok to rac3
     //  and returns a reference to rac3 (which we ignore here):
     tok.toContainer(rac3);
     \endcode
 
     This gives you maximum flexibility in how you want the sequence to
     be stored.
 */
 
 /*!
     \fn QStringTokenizer::toContainer(Container &&c) const &&
     \overload
 
     In addition to the constraints on the lvalue-this overload, this
     rvalue-this overload is only available when this QStringTokenizer
     does not store the haystack internally, as this could create a
     container full of dangling references:
 
     \code
     auto tokens = QStringTokenizer{widget.text(), u','}.toContainer();
     // ERROR: cannot call toContainer() on rvalue
     // 'tokens' references the data of the copy of widget.text()
     // stored inside the QStringTokenizer, which has since been deleted
     \endcode
 
     To fix, store the QStringTokenizer in a temporary:
 
     \code
     auto tokenizer = QStringTokenizer{widget.text90, u','};
     auto tokens = tokenizer.toContainer();
     // OK: the copy of widget.text() stored in 'tokenizer' keeps the data
     // referenced by 'tokens' alive.
     \endcode
 
     You can force this function into existence by passing a view instead:
 
     \code
     func(QStringTokenizer{QStringView{widget.text()}, u','}.toContainer());
     // OK: compiler keeps widget.text() around until after func() has executed
     \endcode
 */
 
 /*!
     \fn qTokenize(Haystack &&haystack, Needle &&needle, Flags...flags)
     \relates QStringTokenizer
 
     Factory function for QStringTokenizer. You can use this function
     if your compiler doesn't, yet, support C++17 Class Template
     Argument Deduction (CTAD), but we recommend direct use of
     QStringTokenizer with CTAD instead.
 */