1 files changed, 89 insertions, 0 deletions
diff --git a/layout/generic/nsIntervalSet.h b/layout/generic/nsIntervalSet.h
new file mode 100644
index 000000000..9941df447
--- /dev/null
+++ b/layout/generic/nsIntervalSet.h
@@ -0,0 +1,89 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+// vim:cindent:ts=8:et:sw=4:
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* a set of ranges on a number-line */
+
+#ifndef nsIntervalSet_h___
+#define nsIntervalSet_h___
+
+#include "nsCoord.h"
+
+typedef void *
+(* IntervalSetAlloc)(size_t aBytes, void *aClosure);
+
+typedef void
+(* IntervalSetFree) (size_t aBytes, void *aPtr, void *aClosure);
+
+/*
+ * A list-based class (hopefully tree-based when I get around to it)
+ * for representing a set of ranges on a number-line.
+ */
+class nsIntervalSet {
+
+public:
+
+    typedef nscoord coord_type;
+
+    nsIntervalSet(IntervalSetAlloc aAlloc, IntervalSetFree aFree,
+                  void* aAllocatorClosure);
+    ~nsIntervalSet();
+
+    /*
+     * Include the interval [aBegin, aEnd] in the set.
+     *
+     * Removal of intervals added is not supported because that would
+     * require keeping track of the individual intervals that were
+     * added (nsIntervalMap should do that).  It would be simple to
+     * implement ExcludeInterval if anyone wants it, though.
+     */
+    void IncludeInterval(coord_type aBegin, coord_type aEnd);
+
+    /*
+     * Are _some_ points in [aBegin, aEnd] contained within the set
+     * of intervals?
+     */
+    bool Intersects(coord_type aBegin, coord_type aEnd) const;
+
+    /*
+     * Are _all_ points in [aBegin, aEnd] contained within the set
+     * of intervals?
+     */
+    bool Contains(coord_type aBegin, coord_type aEnd) const;
+
+    bool IsEmpty() const
+    {
+        return !mList;
+    }
+
+private:
+
+    class Interval {
+
+    public:
+        Interval(coord_type aBegin, coord_type aEnd)
+            : mBegin(aBegin),
+              mEnd(aEnd),
+              mPrev(nullptr),
+              mNext(nullptr)
+        {
+        }
+
+        coord_type mBegin;
+        coord_type mEnd;
+        Interval *mPrev;
+        Interval *mNext;
+    };
+
+    void FreeInterval(Interval *aInterval);
+
+    Interval           *mList;
+    IntervalSetAlloc    mAlloc;
+    IntervalSetFree     mFree;
+    void               *mAllocatorClosure;
+        
+};
+
+#endif // !defined(nsIntervalSet_h___)