1 files changed, 62 insertions, 0 deletions
diff --git a/pkg/usermem/addr_range.go b/pkg/usermem/addr_range.go
new file mode 100755
index 000000000..152ed1434
--- /dev/null
+++ b/pkg/usermem/addr_range.go
@@ -0,0 +1,62 @@
+package usermem
+
+// A Range represents a contiguous range of T.
+//
+// +stateify savable
+type AddrRange struct {
+	// Start is the inclusive start of the range.
+	Start Addr
+
+	// End is the exclusive end of the range.
+	End Addr
+}
+
+// WellFormed returns true if r.Start <= r.End. All other methods on a Range
+// require that the Range is well-formed.
+func (r AddrRange) WellFormed() bool {
+	return r.Start <= r.End
+}
+
+// Length returns the length of the range.
+func (r AddrRange) Length() Addr {
+	return r.End - r.Start
+}
+
+// Contains returns true if r contains x.
+func (r AddrRange) Contains(x Addr) bool {
+	return r.Start <= x && x < r.End
+}
+
+// Overlaps returns true if r and r2 overlap.
+func (r AddrRange) Overlaps(r2 AddrRange) 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 AddrRange) IsSupersetOf(r2 AddrRange) 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 AddrRange) Intersect(r2 AddrRange) AddrRange {
+	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 AddrRange) CanSplitAt(x Addr) bool {
+	return r.Contains(x) && r.Start < x
+}