Kernel: Rename Range => VirtualRange

...and also RangeAllocator => VirtualRangeAllocator.

This clarifies that the ranges we're dealing with are *virtual* memory
ranges and not anything else.

Kernel/Memory/VirtualRange.cpp

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, Leon Albrecht <leon2002.la@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Vector.h>
+#include <Kernel/Memory/MemoryManager.h>
+#include <Kernel/Memory/VirtualRange.h>
+#include <LibC/limits.h>
+
+namespace Kernel::Memory {
+
+Vector<VirtualRange, 2> VirtualRange::carve(VirtualRange const& taken) const
+{
+    VERIFY((taken.size() % PAGE_SIZE) == 0);
+
+    Vector<VirtualRange, 2> parts;
+    if (taken == *this)
+        return {};
+    if (taken.base() > base())
+        parts.append({ base(), taken.base().get() - base().get() });
+    if (taken.end() < end())
+        parts.append({ taken.end(), end().get() - taken.end().get() });
+    return parts;
+}
+VirtualRange VirtualRange::intersect(VirtualRange const& other) const
+{
+    if (*this == other) {
+        return *this;
+    }
+    auto new_base = max(base(), other.base());
+    auto new_end = min(end(), other.end());
+    VERIFY(new_base < new_end);
+    return VirtualRange(new_base, (new_end - new_base).get());
+}
+
+KResultOr<VirtualRange> VirtualRange::expand_to_page_boundaries(FlatPtr address, size_t size)
+{
+    if (page_round_up_would_wrap(size))
+        return EINVAL;
+
+    if ((address + size) < address)
+        return EINVAL;
+
+    if (page_round_up_would_wrap(address + size))
+        return EINVAL;
+
+    auto base = VirtualAddress { address }.page_base();
+    auto end = page_round_up(address + size);
+
+    return VirtualRange { base, end - base.get() };
+}
+
+}