[libcalamares] Introduce helper NamedSuffix template

For (all?) those cases where we have configuration with
a value followed by a unit, introduce a class that
uses the NamedEnum properties to make parsing and split-up easier.

src/libcalamares/utils/NamedSuffix.h

@@ -0,0 +1,62 @@
+/* === This file is part of Calamares - <https://github.com/calamares> ===
+ *
+ *   Copyright 2019, Adriaan de Groot <groot@kde.org>
+ *
+ *   Calamares is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   Calamares is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with Calamares. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @brief Support for unit-suffixed values.
+ */
+
+#ifndef LIBCALAMARES_NAMEDSUFFIX_H
+#define LIBCALAMARES_NAMEDSUFFIX_H
+
+#include "NamedEnum.h"
+
+template<typename T, T none>
+class NamedSuffix
+{
+public:
+    using unit_t = T;
+
+    NamedSuffix()
+        : m_value(0)
+        , m_unit( none )
+    {
+    }
+
+    int value() const { return m_value; }
+    T unit() const { return m_unit; }
+
+    bool isValid() const { return m_unit != none; }
+
+protected:
+    NamedSuffix( const NamedEnumTable<T>& table, const QString& s )
+        : NamedSuffix()
+    {
+        for( const auto suffix : table.table )
+            if ( s.endsWith( suffix.first ) )
+            {
+                m_value = s.left( s.length() - suffix.first.length() + 1 ).toInt();
+                m_unit = suffix.second;
+                break;
+            }
+    }
+
+    int m_value;
+    T m_unit;
+};
+
+
+#endif