Implement the run run intersect_with operation

src/bitmap/store.rs

@@ -514,8 +514,36 @@ impl Store {
             }
             // TODO(jpg) intersect_with bitmap, run
             (_this @ &mut Bitmap(..), &Run(..)) => unimplemented!(),
-            // TODO(jpg) intersect_with run, *
-            (&mut Run(ref mut _intervals1), &Run(ref _intervals2)) => unimplemented!(),
+            (&mut Run(ref mut intervals1), &Run(ref intervals2)) => {
+                let mut merged = Vec::new();
+
+                let (mut i1, mut i2) = (intervals1.iter(), intervals2.iter());
+                let (mut iv1, mut iv2) = (i1.next(), i2.next());
+                loop {
+                    if let (Some(v1), Some(v2)) = (iv1, iv2) {
+                        let start = cmp::max(v1.start, v2.start);
+                        let end = cmp::min(v1.end, v2.end);
+                        let iv = Interval::new(start, end);
+                        if iv.run_len() > 0 {
+                            merged.push(iv);
+                        }
+                    }
+
+                    // Iterate over two iterators, consuming the lowest first, like merge join.
+                    match (iv1, iv2) {
+                        (None, None) => break,
+                        (Some(v1), None) => iv1 = i1.next(),
+                        (None, Some(v2)) => iv2 = i2.next(),
+                        (Some(v1), Some(v2)) => match v1.start.cmp(&v2.start) {
+                            Equal => { iv1 = i1.next(); iv2 = i2.next(); },
+                            Less => iv1 = i1.next(),
+                            Greater => iv2 = i2.next(),
+                        },
+                    }
+                }
+
+                *intervals1 = merged;
+            },
             (this @ &mut Run(..), &Array(..)) => {
                 let mut new = other.clone();
                 new.intersect_with(this);