1 files changed, 77 insertions, 0 deletions
diff --git a/pkg/segment/range.go b/pkg/segment/range.go
new file mode 100644
index 000000000..5ff30d489
--- /dev/null
+++ b/pkg/segment/range.go
@@ -0,0 +1,77 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package segment
+
+// T is a required type parameter that must be an integral type.
+type T uint64
+
+// A Range represents a contiguous range of T.
+type Range struct {
+	// Start is the inclusive start of the range.
+	Start T
+
+	// End is the exclusive end of the range.
+	End T
+}
+
+// WellFormed returns true if r.Start <= r.End. All other methods on a Range
+// require that the Range is well-formed.
+func (r Range) WellFormed() bool {
+	return r.Start <= r.End
+}
+
+// Length returns the length of the range.
+func (r Range) Length() T {
+	return r.End - r.Start
+}
+
+// Contains returns true if r contains x.
+func (r Range) Contains(x T) bool {
+	return r.Start <= x && x < r.End
+}
+
+// Overlaps returns true if r and r2 overlap.
+func (r Range) Overlaps(r2 Range) bool {
+	return r.Start < r2.End && r2.Start < r.End
+}
+
+// IsSupersetOf returns true if r is a superset of r2; that is, the range r2 is
+// contained within r.
+func (r Range) IsSupersetOf(r2 Range) bool {
+	return r.Start <= r2.Start && r.End >= r2.End
+}
+
+// Intersect returns a range consisting of the intersection between r and r2.
+// If r and r2 do not overlap, Intersect returns a range with unspecified
+// bounds, but for which Length() == 0.
+func (r Range) Intersect(r2 Range) Range {
+	if r.Start < r2.Start {
+		r.Start = r2.Start
+	}
+	if r.End > r2.End {
+		r.End = r2.End
+	}
+	if r.End < r.Start {
+		r.End = r.Start
+	}
+	return r
+}
+
+// CanSplitAt returns true if it is legal to split a segment spanning the range
+// r at x; that is, splitting at x would produce two ranges, both of which have
+// non-zero length.
+func (r Range) CanSplitAt(x T) bool {
+	return r.Contains(x) && r.Start < x
+}