interval: add extend and intersect

Signed-off-by: Simon Rozman <simon.rozman@amebis.si>

include/stdex/interval.hpp

@@ -227,6 +227,54 @@ namespace stdex
 		{
 			return !operator ==(other);
 		}
+
+		///
+		/// Extends the interval to another interval
+		/// 
+		/// \note Makes a union of two intervals, so it covers [min(start, other.start), max(end, other.end)).
+		/// When either of the intervals is empty, the result is the non-empty one.
+		/// When both intervals are empty, the result is an empty interval.
+		///
+		/// \param[in] other  Interval to extend to
+		///
+		/// \returns Resulting interval
+		///
+		interval extend(_In_ const interval& other)
+		{
+			if (other.empty())
+				return *this;
+			if (empty())
+				return *this = other;
+			if (other.start < start)
+				start = other.start;
+			if (end < other.end)
+				end = other.end;
+			return *this;
+		}
+
+		///
+		/// Intersects the interval with another interval
+		/// 
+		/// \note Makes an intersection of two intervals, so it covers [max(start, other.start), min(end, other.end)).
+		/// When intervals do not interlap, the result is an invalid interval.
+		/// When any of the intervals is empty, the result is an invalid (and empty by definition) interval.
+		///
+		/// \param[in] other  Interval to intersect with
+		///
+		/// \returns Resulting interval
+		///
+		interval intersect(_In_ const interval& other)
+		{
+			if (empty() || other.empty()) {
+				invalidate();
+				return *this;
+			}
+			if (start < other.start)
+				start = other.start;
+			if (other.end < end)
+				end = other.end;
+			return *this;
+		}
 	};
 
 	template <class T, class AX = std::allocator<interval<T>>>