Add class TSpan<T>

README.md

@@ -152,6 +152,7 @@ See the [Turbo Vision 2.0 Programming Guide](https://archive.org/details/bitsave
 * `TRect` methods `move`, `grow`, `intersect` and `Union` now return `TRect&` instead of being `void`, so that they can be chained.
 * `TOutlineViewer` now allows the root node to have siblings.
 * New class `TStringView`, which is a clone of `std::string_view`. You shouldn't need it unless you are programming in Borland C++, which has no `std::string_view`.
+* New class `TSpan<T>`, a generic (and non-const) version of `TStringView`, inspired by `std::span`.
 * New classes `TDrawSurface` and `TSurfaceView`, see `<include/surface.h>`.
 * Unicode support, see below.
 

include/tvision/ttypes.h

@@ -73,4 +73,112 @@ extern const uchar specialChars[];
 #define _genInt(i) __int__(i)
 #endif
 
+#ifdef __BORLANDC__
+#define constexpr
+#endif
+
+template <class T>
+class TSpan {
+
+    // This is actually a generalization of TStringView for any kind of element
+    // type (and with no 'const' by default).
+    // It exists for compatibility with Borland C++ and because std::span (C++ 20)
+    // may not be widely available yet.
+
+    T _FAR *ptr;
+    size_t len;
+
+public:
+
+    constexpr TSpan();
+    constexpr TSpan(T _FAR *first, size_t n);
+
+    constexpr T _FAR * data() const;
+    constexpr size_t size() const;
+    constexpr size_t size_bytes() const;
+    constexpr Boolean empty() const;
+    constexpr T _FAR & operator[](size_t pos) const;
+    constexpr T _FAR & front() const;
+    constexpr T _FAR & back() const;
+
+    constexpr TSpan subspan(size_t pos) const;
+    constexpr TSpan subspan(size_t pos, size_t n) const;
+
+};
+
+template <class T>
+inline constexpr TSpan<T>::TSpan() :
+    ptr(0),
+    len(0)
+{
+}
+
+template <class T>
+inline constexpr TSpan<T>::TSpan(T _FAR *first, size_t n) :
+    ptr(first),
+    len(n)
+{
+}
+
+template <class T>
+inline constexpr T _FAR * TSpan<T>::data() const
+{
+    return ptr;
+}
+
+template <class T>
+inline constexpr size_t TSpan<T>::size() const
+{
+    return len;
+}
+
+template <class T>
+inline constexpr size_t TSpan<T>::size_bytes() const
+{
+    return size()*sizeof(T);
+}
+
+template <class T>
+inline constexpr Boolean TSpan<T>::empty() const
+{
+    return size() == 0;
+}
+
+template <class T>
+inline constexpr T _FAR & TSpan<T>::operator[](size_t pos) const
+{
+    return ptr[pos];
+}
+
+template <class T>
+inline constexpr T _FAR & TSpan<T>::front() const
+{
+    return ptr[0];
+}
+
+template <class T>
+inline constexpr T _FAR & TSpan<T>::back() const
+{
+    return ptr[len - 1];
+}
+
+template <class T>
+inline constexpr TSpan<T> TSpan<T>::subspan(size_t pos) const
+{
+    return TSpan<T>(ptr + pos, len - pos);
+}
+
+template <class T>
+inline constexpr TSpan<T> TSpan<T>::subspan(size_t pos, size_t n) const
+{
+    size_t tail = len - pos;
+    if (n > tail)
+        n = tail;
+    return TSpan<T>(ptr + pos, n);
+}
+
+#ifdef __BORLANDC__
+#undef constexpr
+#endif
+
 #endif  // __TTYPES_H