AK: Add generic SimpleIterator class to replace VectorIterator.

AK/Iterator.h

@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+
+namespace AK {
+
+template<typename Container, typename ValueType>
+class SimpleIterator {
+public:
+    friend Container;
+
+    constexpr bool is_end() const { return m_index == SimpleIterator::end(m_container).m_index; }
+    constexpr size_t index() const { return m_index; }
+
+    constexpr bool operator==(SimpleIterator other) const { return m_index == other.m_index; }
+    constexpr bool operator!=(SimpleIterator other) const { return m_index != other.m_index; }
+    constexpr bool operator<(SimpleIterator other) const { return m_index < other.m_index; }
+    constexpr bool operator>(SimpleIterator other) const { return m_index > other.m_index; }
+    constexpr bool operator<=(SimpleIterator other) const { return m_index <= other.m_index; }
+    constexpr bool operator>=(SimpleIterator other) const { return m_index >= other.m_index; }
+
+    constexpr SimpleIterator operator+(ptrdiff_t delta) const { return SimpleIterator { m_container, m_index + delta }; }
+    constexpr SimpleIterator operator-(ptrdiff_t delta) const { return SimpleIterator { m_container, m_index - delta }; }
+
+    constexpr ptrdiff_t operator-(SimpleIterator other) const { return static_cast<ptrdiff_t>(m_index) - other.m_index; }
+
+    constexpr SimpleIterator operator++()
+    {
+        ++m_index;
+        return *this;
+    }
+    constexpr SimpleIterator operator++(int)
+    {
+        ++m_index;
+        return SimpleIterator { m_container, m_index - 1 };
+    }
+
+    constexpr SimpleIterator operator--()
+    {
+        --m_index;
+        return *this;
+    }
+    constexpr SimpleIterator operator--(int)
+    {
+        --m_index;
+        return SimpleIterator { m_container, m_index + 1 };
+    }
+
+    constexpr const ValueType& operator*() const { return m_container[m_index]; }
+    constexpr ValueType& operator*() { return m_container[m_index]; }
+
+    constexpr const ValueType* operator->() const { return &m_container[m_index]; }
+    constexpr ValueType* operator->() { return &m_container[m_index]; }
+
+private:
+    static constexpr SimpleIterator begin(Container& container) { return { container, 0 }; }
+    static constexpr SimpleIterator end(Container& container)
+    {
+        using RawContainerType = typename RemoveCV<Container>::Type;
+
+        if constexpr (IsSame<StringView, RawContainerType>::value || IsSame<String, RawContainerType>::value)
+            return { container, container.length() };
+        else
+            return { container, container.size() };
+    }
+
+    constexpr SimpleIterator(Container& container, size_t index)
+        : m_container(container)
+        , m_index(index)
+    {
+    }
+
+    Container& m_container;
+    size_t m_index;
+};
+
+}