add a memoryview class

memoryview is a non owning typed view over a memory range, usefull
to pass arrays as parameters without data copying.

src/memoryview.hh

@@ -0,0 +1,58 @@
+#ifndef memoryview_hh_INCLUDED
+#define memoryview_hh_INCLUDED
+
+#include <vector>
+#include <initializer_list>
+
+namespace Kakoune
+{
+
+// A memoryview provides a typed, non owning view of a memory
+// range with an interface similar to std::vector.
+template<typename T>
+class memoryview
+{
+public:
+    memoryview()
+        : m_pointer(nullptr), m_size(0) {}
+
+    memoryview(const T& oneval)
+        : m_pointer(&oneval), m_size(1) {}
+
+    memoryview(const T* pointer, size_t size)
+        : m_pointer(pointer), m_size(size) {}
+
+    memoryview(const T* begin, const T* end)
+        : m_pointer(begin), m_size(end - begin) {}
+
+    memoryview(const std::vector<T>& v)
+        : m_pointer(&v[0]), m_size(v.size()) {}
+
+    memoryview(const std::initializer_list<T>& v)
+        : m_pointer(v.begin()), m_size(v.size()) {}
+
+    size_t size() const { return m_size; }
+    const T& operator[](size_t n) const { return *(m_pointer + n); }
+
+    const T* begin() const { return m_pointer; }
+    const T* end()   const { return m_pointer+m_size; }
+
+    const T& front() const { return *m_pointer; }
+    const T& back()  const { return *(m_pointer + m_size - 1); }
+
+    bool empty() const { return m_size == 0; }
+
+    memoryview subrange(size_t first, size_t count) const
+    {
+        return memoryview(m_pointer + first, count);
+    }
+
+private:
+    const T* m_pointer;
+    size_t   m_size;
+};
+
+}
+
+#endif // memoryview_hh_INCLUDED
+