Disentangle string-related headers

It's starting to hinder QStringView development
(QString::append(QStringView), e.g.).

- qbytearray.h includes qstring.h, but is included by qstring.h
  -> remove qstring.h include from qbytearray.h

- the QStringLiteral definition is used from both qstring.h and
  qstringview.h
  -> extract into its own header, move QStringViewLiteral definition
     there, too

- the qCompareStrings(), qConvertTo*() functions are used by QString
  and QStringView
  -> also extract into own header, included from qstring.h and
     qstringview.h

- QStringView::toString() depends on QString, which depends on
  QStringView
  -> move QStringView::toString() definition to qstring.h, after the
     definition of QString
  -> move qstringview.h up to all the other includes in qstring.h

This is starting to look like a DAG again, and allows to remove the
unholy

  #ifndef QSTRING_H
  #  include <qstring.h>
  #endif

hack from qstringview.h.

[ChangeLog][Potentially Source-Incompatible Changes][QByteArray]
qbytearray.h no longer includes qstring.h. In particular, this means
that in order to use QStringBuilder with QByteArray, you need to
include both qbytearray.h and qstring.h now (or <QByteArray> and
<QString>, resp.).

Change-Id: I7f8acf9c11bc1731266cd25c6eda9fb36723f364
Reviewed-by: Anton Kudryavtsev <antkudr@mail.ru>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

1 files changed, 68 insertions, 0 deletions

diff --git a/src/corelib/tools/qstringalgorithms.h b/src/corelib/tools/qstringalgorithms.h
new file mode 100644
index 0000000000..29fefd4cf5
--- /dev/null
+++ b/src/corelib/tools/qstringalgorithms.h
@@ -0,0 +1,68 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
+** Contact: https://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 QSTRINGALGORITHMS_H
+#define QSTRINGALGORITHMS_H
+
+#include <QtCore/qnamespace.h>
+
+#if 0
+#pragma qt_class(QStringAlgorithms)
+#endif
+
+QT_BEGIN_NAMESPACE
+
+class QByteArray;
+class QLatin1String;
+class QStringView;
+template <typename T> class QVector;
+
+Q_CORE_EXPORT Q_DECL_PURE_FUNCTION int qCompareStrings(QStringView   lhs, QStringView   rhs, Qt::CaseSensitivity cs = Qt::CaseSensitive) Q_DECL_NOTHROW Q_REQUIRED_RESULT;
+Q_CORE_EXPORT Q_DECL_PURE_FUNCTION int qCompareStrings(QStringView   lhs, QLatin1String rhs, Qt::CaseSensitivity cs = Qt::CaseSensitive) Q_DECL_NOTHROW Q_REQUIRED_RESULT;
+Q_CORE_EXPORT Q_DECL_PURE_FUNCTION int qCompareStrings(QLatin1String lhs, QStringView   rhs, Qt::CaseSensitivity cs = Qt::CaseSensitive) Q_DECL_NOTHROW Q_REQUIRED_RESULT;
+Q_CORE_EXPORT Q_DECL_PURE_FUNCTION int qCompareStrings(QLatin1String lhs, QLatin1String rhs, Qt::CaseSensitivity cs = Qt::CaseSensitive) Q_DECL_NOTHROW Q_REQUIRED_RESULT;
+
+Q_CORE_EXPORT QByteArray qConvertToLatin1(QStringView str) Q_REQUIRED_RESULT;
+Q_CORE_EXPORT QByteArray qConvertToUtf8(QStringView str) Q_REQUIRED_RESULT;
+Q_CORE_EXPORT QByteArray qConvertToLocal8Bit(QStringView str) Q_REQUIRED_RESULT;
+Q_CORE_EXPORT QVector<uint> qConvertToUcs4(QStringView str) Q_REQUIRED_RESULT;
+
+QT_END_NAMESPACE
+
+#endif // QSTRINGALGORTIHMS_H