diff options
Diffstat (limited to 'src/corelib/tools/qstringview.h')
| -rw-r--r-- | src/corelib/tools/qstringview.h | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/src/corelib/tools/qstringview.h b/src/corelib/tools/qstringview.h new file mode 100644 index 0000000000..5384e73039 --- /dev/null +++ b/src/corelib/tools/qstringview.h @@ -0,0 +1,226 @@ +/**************************************************************************** +** +** Copyright (C) 2017 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com> +** Contact: http://www.qt.io/licensing/ +** +** This file is part of the QtCore module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** Commercial License Usage +** Licensees holding valid commercial Qt licenses may use this file in +** accordance with the commercial license agreement provided with the +** Software or, alternatively, in accordance with the terms contained in +** a written agreement between you and The Qt Company. For licensing terms +** and conditions see https://www.qt.io/terms-conditions. For further +** information use the contact form at https://www.qt.io/contact-us. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 3 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL3 included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 3 requirements +** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 2.0 or (at your option) the GNU General +** Public license version 3 or any later version approved by the KDE Free +** Qt Foundation. The licenses are as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 +** included in the packaging of this file. Please review the following +** information to ensure the GNU General Public License requirements will +** be met: https://www.gnu.org/licenses/gpl-2.0.html and +** https://www.gnu.org/licenses/gpl-3.0.html. +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#ifndef QSTRING_H +# include <QtCore/qstring.h> +#endif + +#ifndef QSTRINGVIEW_H +#define QSTRINGVIEW_H + +#include <string> + +QT_BEGIN_NAMESPACE + +#ifndef QT_NO_UNICODE_LITERAL +# ifndef QT_UNICODE_LITERAL +# error "If you change QStringLiteral, please change QStringViewLiteral, too" +# endif +# define QStringViewLiteral(str) QStringView(QT_UNICODE_LITERAL(str), sizeof(str) - 1) +#endif + +namespace QtPrivate { +template <typename Char> +struct IsCompatibleCharTypeHelper + : std::integral_constant<bool, + std::is_same<Char, QChar>::value || + std::is_same<Char, ushort>::value || +#if !defined(Q_OS_WIN) || defined(Q_COMPILER_UNICODE_STRINGS) + std::is_same<Char, char16_t>::value || +#endif + (std::is_same<Char, wchar_t>::value && sizeof(wchar_t) == sizeof(QChar))> {}; +template <typename Char> +struct IsCompatibleCharType + : IsCompatibleCharTypeHelper<typename std::remove_cv<typename std::remove_reference<Char>::type>::type> {}; + +template <typename T> +struct IsCompatibleStdBasicStringHelper : std::false_type {}; +template <typename Char, typename...Args> +struct IsCompatibleStdBasicStringHelper<std::basic_string<Char, Args...> > + : IsCompatibleCharType<Char> {}; + +template <typename T> +struct IsCompatibleStdBasicString + : IsCompatibleStdBasicStringHelper< + typename std::remove_cv<typename std::remove_reference<T>::type>::type + > {}; + +} // namespace QtPrivate + +class QStringView +{ +#if defined(Q_OS_WIN) && !defined(Q_COMPILER_UNICODE_STRINGS) + typedef wchar_t storage_type; +#else + typedef char16_t storage_type; +#endif +public: + typedef const QChar value_type; + typedef std::ptrdiff_t difference_type; + typedef QIntegerForSizeof<size_t>::Signed size_type; + typedef value_type &reference; + typedef value_type &const_reference; + typedef value_type *pointer; + typedef value_type *const_pointer; + + typedef pointer iterator; + typedef const_pointer const_iterator; + typedef std::reverse_iterator<iterator> reverse_iterator; + typedef std::reverse_iterator<const_iterator> const_reverse_iterator; + +private: + template <typename Char> + using if_compatible_char = typename std::enable_if<QtPrivate::IsCompatibleCharType<Char>::value, bool>::type; + + template <typename T> + using if_compatible_string = typename std::enable_if<QtPrivate::IsCompatibleStdBasicString<T>::value, bool>::type; + + template <typename Char> + static Q_DECL_RELAXED_CONSTEXPR size_type lengthHelper(const Char *str) Q_DECL_NOTHROW + { + size_type result = 0; + while (*str++) + ++result; + return result; + } + static Q_DECL_RELAXED_CONSTEXPR size_type lengthHelper(const QChar *str) Q_DECL_NOTHROW + { + size_type result = 0; + while (!str++->isNull()) + ++result; + return result; + } + + template <typename Char> + static const storage_type *castHelper(const Char *str) Q_DECL_NOTHROW + { return reinterpret_cast<const storage_type*>(str); } + static Q_DECL_CONSTEXPR const storage_type *castHelper(const storage_type *str) Q_DECL_NOTHROW + { return str; } + + // prevent + // T t; QStringView sv(t), T \in {QChar, QLatin1String, QByteArray, const char*} + // from compiling as QStringView sv(QString(t)): + QStringView(QChar) = delete; + QStringView(QLatin1String) = delete; + QStringView(const QByteArray &) = delete; + QStringView(const char *) = delete; + +#ifdef Q_OS_WIN + // prevent QStringView(Char), Char compatible, from compiling due to: + // https://connect.microsoft.com/VisualStudio/feedback/details/2256407/c-two-user-defined-conversions-incorrectly-accepted-in-implicit-conversion-sequence + template <typename Char, if_compatible_char<Char> = true> + QStringView(Char) = delete; +#endif +public: + Q_DECL_CONSTEXPR QStringView() Q_DECL_NOTHROW + : m_size(0), m_data(nullptr) {} + Q_DECL_CONSTEXPR QStringView(std::nullptr_t) Q_DECL_NOTHROW + : QStringView() {} +#if QT_DEPRECATED_SINCE(5, 9) + Q_DECL_CONSTEXPR QStringView(QString::Null) Q_DECL_NOTHROW + : QStringView() {} +#endif + + template <typename Char, if_compatible_char<Char> = true> + Q_DECL_CONSTEXPR QStringView(const Char *str, size_type len) + : m_size((Q_ASSERT(len >= 0), Q_ASSERT(str || !len), len)), + m_data(castHelper(str)) {} + + template <typename Char, if_compatible_char<Char> = true> + Q_DECL_CONSTEXPR QStringView(const Char *str) + : QStringView(str, str ? lengthHelper(str) : 0) {} + + QStringView(const QString &str) Q_DECL_NOTHROW + : QStringView(str.isNull() ? nullptr : str.data(), size_type(str.size())) {} + QStringView(const QStringRef &str) Q_DECL_NOTHROW + : QStringView(str.isNull() ? nullptr : str.data(), size_type(str.size())) {} + + template <typename StdBasicString, if_compatible_string<StdBasicString> = true> + QStringView(const StdBasicString &str) Q_DECL_NOTHROW + : QStringView(str.data(), size_type(str.size())) {} + + QString toString() const { return Q_ASSERT(size() == length()), QString(data(), length()); } + + Q_DECL_CONSTEXPR size_type size() const Q_DECL_NOTHROW { return m_size; } + const_pointer data() const Q_DECL_NOTHROW { return reinterpret_cast<const_pointer>(m_data); } + Q_DECL_CONSTEXPR const storage_type *utf16() const Q_DECL_NOTHROW { return m_data; } + + Q_DECL_CONSTEXPR QChar operator[](size_type n) const + { return Q_ASSERT(n >= 0), Q_ASSERT(n < size()), QChar(m_data[n]); } + + // + // QString API + // + + Q_DECL_CONSTEXPR QChar at(size_type n) const { return (*this)[n]; } + + // + // STL compatibility API: + // + const_iterator begin() const Q_DECL_NOTHROW { return data(); } + const_iterator end() const Q_DECL_NOTHROW { return data() + size(); } + const_iterator cbegin() const Q_DECL_NOTHROW { return begin(); } + const_iterator cend() const Q_DECL_NOTHROW { return end(); } + const_reverse_iterator rbegin() const Q_DECL_NOTHROW { return const_reverse_iterator(end()); } + const_reverse_iterator rend() const Q_DECL_NOTHROW { return const_reverse_iterator(begin()); } + const_reverse_iterator crbegin() const Q_DECL_NOTHROW { return rbegin(); } + const_reverse_iterator crend() const Q_DECL_NOTHROW { return rend(); } + + Q_DECL_CONSTEXPR bool empty() const Q_DECL_NOTHROW { return size() == 0; } + Q_DECL_CONSTEXPR QChar front() const { return Q_ASSERT(!empty()), QChar(m_data[0]); } + Q_DECL_CONSTEXPR QChar back() const { return Q_ASSERT(!empty()), QChar(m_data[m_size - 1]); } + + // + // Qt compatibility API: + // + Q_DECL_CONSTEXPR bool isNull() const Q_DECL_NOTHROW { return !m_data; } + Q_DECL_CONSTEXPR bool isEmpty() const Q_DECL_NOTHROW { return empty(); } + Q_DECL_CONSTEXPR int length() const /* not nothrow! */ + { return Q_ASSERT(int(size()) == size()), int(size()); } + Q_DECL_CONSTEXPR QChar first() const { return front(); } + Q_DECL_CONSTEXPR QChar last() const { return back(); } +private: + size_type m_size; + const storage_type *m_data; +}; +Q_DECLARE_TYPEINFO(QStringView, Q_MOVABLE_TYPE); + +QT_END_NAMESPACE + +#endif /* QSTRINGVIEW_H */ |