Simplify and unify Q{ByteArray,String{,Ref}}::{simplify,trimmed}

As a side effect, QString::simplified() will always return a detached
copy, even if it's the same contents.

QStringRef::trimmed() can use the same calculation algorithm but can't
use the trimmed_helper() template function due to its lack of a
constructor taking begin pointer and size (std::string_view could do
it). That constructor can't be added because QStringRef always refers to
an existing QString, not to data in memory.

Change-Id: Ib966c1741819c68c6bac5fcbb00f8ac818b3ccab
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

1 files changed, 135 insertions, 0 deletions

diff --git a/src/corelib/tools/qstringalgorithms_p.h b/src/corelib/tools/qstringalgorithms_p.h
new file mode 100644
index 0000000000..5a68260c59
--- /dev/null
+++ b/src/corelib/tools/qstringalgorithms_p.h
@@ -0,0 +1,135 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Intel Corporation.
+** Contact: http://www.qt-project.org/legal
+**
+** 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 Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/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 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QSTRINGALGORITHMS_P_H
+#define QSTRINGALGORITHMS_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists for the convenience
+// of internal files.  This header file may change from version to version
+// without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "qstring.h"
+#include "qlocale_p.h"      // for ascii_isspace
+
+QT_BEGIN_NAMESPACE
+
+template <typename StringType> struct QStringAlgorithms
+{
+    typedef typename StringType::value_type Char;
+    typedef typename StringType::size_type size_type;
+    typedef typename QtPrivate::remove_cv<StringType>::type NakedStringType;
+    static const bool isConst = QtPrivate::is_const<StringType>::value;
+
+    static inline bool isSpace(char ch) { return ascii_isspace(ch); }
+    static inline bool isSpace(QChar ch) { return ch.isSpace(); }
+
+    // Surrogate pairs are not handled in either of the functions below. That is
+    // not a problem because there are no space characters (Zs, Zl, Zp) outside the
+    // Basic Multilingual Plane.
+
+    static inline void trimmed_helper_positions(const Char *&begin, const Char *&end)
+    {
+        // skip white space from start
+        while (begin < end && isSpace(*begin))
+            begin++;
+        // skip white space from end
+        if (begin < end) {
+            while (begin < end && isSpace(end[-1]))
+                end--;
+        }
+    }
+
+    static inline StringType trimmed_helper(StringType &str)
+    {
+        const Char *begin = str.cbegin();
+        const Char *end = str.cend();
+        trimmed_helper_positions(begin, end);
+
+        if (begin == str.cbegin() && end == str.cend())
+            return str;
+        if (begin == end)
+            return StringType();
+        return StringType(begin, end - begin);
+    }
+
+    static inline StringType simplified_helper(StringType &str)
+    {
+        if (str.isEmpty())
+            return str;
+        const Char *src = str.cbegin();
+        const Char *end = str.cend();
+        NakedStringType result(str.size(), Qt::Uninitialized);
+
+        Char *dst = const_cast<Char *>(result.cbegin());
+        Char *ptr = dst;
+        forever {
+            while (src != end && isSpace(*src))
+                ++src;
+            while (src != end && !isSpace(*src))
+                *ptr++ = *src++;
+            if (src != end)
+                *ptr++ = QChar::Space;
+            else
+                break;
+        }
+        if (ptr != dst && ptr[-1] == QChar::Space)
+            --ptr;
+
+        int newlen = ptr - dst;
+        if (newlen == str.size()) {
+            // nothing happened, return the original
+            return str;
+        }
+        result.resize(ptr - dst);
+        return qMove(result);
+    }
+};
+
+QT_END_NAMESPACE
+
+#endif // QSTRINGALGORITHMS_P_H