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, 128 insertions, 0 deletions

diff --git a/src/corelib/tools/qstringliteral.h b/src/corelib/tools/qstringliteral.h
new file mode 100644
index 0000000000..6a1a74a80e
--- /dev/null
+++ b/src/corelib/tools/qstringliteral.h
@@ -0,0 +1,128 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2016 Intel Corporation.
+** 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 QSTRINGLITERAL_H
+#define QSTRINGLITERAL_H
+
+#include <QtCore/qarraydata.h>
+
+#if 0
+#pragma qt_class(QStringLiteral)
+#endif
+
+QT_BEGIN_NAMESPACE
+
+typedef QTypedArrayData<ushort> QStringData;
+
+#if defined(Q_OS_WIN) && !defined(Q_COMPILER_UNICODE_STRINGS)
+// fall back to wchar_t if the a Windows compiler does not
+// support Unicode string literals, assuming wchar_t is 2 bytes
+// on that platform (sanity-checked by static_assert further below)
+
+#if defined(Q_CC_MSVC)
+#    define QT_UNICODE_LITERAL_II(str) L##str
+#else
+#    define QT_UNICODE_LITERAL_II(str) L"" str
+#endif
+typedef wchar_t qunicodechar;
+
+#else
+// all our supported compilers support Unicode string literals,
+// even if their Q_COMPILER_UNICODE_STRING has been revoked due
+// to lacking stdlib support. But QStringLiteral only needs the
+// core language feature, so just use u"" here unconditionally:
+
+#define QT_UNICODE_LITERAL_II(str) u"" str
+typedef char16_t qunicodechar;
+
+#endif
+
+Q_STATIC_ASSERT_X(sizeof(qunicodechar) == 2,
+        "qunicodechar must typedef an integral type of size 2");
+
+#define QT_UNICODE_LITERAL(str) QT_UNICODE_LITERAL_II(str)
+#define QStringLiteral(str) \
+    ([]() Q_DECL_NOEXCEPT -> QString { \
+        enum { Size = sizeof(QT_UNICODE_LITERAL(str))/2 - 1 }; \
+        static const QStaticStringData<Size> qstring_literal = { \
+            Q_STATIC_STRING_DATA_HEADER_INITIALIZER(Size), \
+            QT_UNICODE_LITERAL(str) }; \
+        QStringDataPtr holder = { qstring_literal.data_ptr() }; \
+        const QString qstring_literal_temp(holder); \
+        return qstring_literal_temp; \
+    }()) \
+    /**/
+
+#define Q_STATIC_STRING_DATA_HEADER_INITIALIZER_WITH_OFFSET(size, offset) \
+    { Q_REFCOUNT_INITIALIZE_STATIC, size, 0, 0, offset } \
+    /**/
+
+#define Q_STATIC_STRING_DATA_HEADER_INITIALIZER(size) \
+    Q_STATIC_STRING_DATA_HEADER_INITIALIZER_WITH_OFFSET(size, sizeof(QStringData)) \
+    /**/
+
+#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))
+#endif
+
+template <int N>
+struct QStaticStringData
+{
+    QArrayData str;
+    qunicodechar data[N + 1];
+
+    QStringData *data_ptr() const
+    {
+        Q_ASSERT(str.ref.isStatic());
+        return const_cast<QStringData *>(static_cast<const QStringData*>(&str));
+    }
+};
+
+struct QStringDataPtr
+{
+    QStringData *ptr;
+};
+
+QT_END_NAMESPACE
+
+#endif // QSTRINGLITERAL_H