1 files changed, 76 insertions, 0 deletions
diff --git a/pkg/sentry/pgalloc/evictable_range.go b/pkg/sentry/pgalloc/evictable_range.go
new file mode 100644
index 000000000..79f513ac2
--- /dev/null
+++ b/pkg/sentry/pgalloc/evictable_range.go
@@ -0,0 +1,76 @@
+package pgalloc
+
+// A Range represents a contiguous range of T.
+//
+// +stateify savable
+type EvictableRange struct {
+	// Start is the inclusive start of the range.
+	Start uint64
+
+	// End is the exclusive end of the range.
+	End uint64
+}
+
+// WellFormed returns true if r.Start <= r.End. All other methods on a Range
+// require that the Range is well-formed.
+//
+//go:nosplit
+func (r EvictableRange) WellFormed() bool {
+	return r.Start <= r.End
+}
+
+// Length returns the length of the range.
+//
+//go:nosplit
+func (r EvictableRange) Length() uint64 {
+	return r.End - r.Start
+}
+
+// Contains returns true if r contains x.
+//
+//go:nosplit
+func (r EvictableRange) Contains(x uint64) bool {
+	return r.Start <= x && x < r.End
+}
+
+// Overlaps returns true if r and r2 overlap.
+//
+//go:nosplit
+func (r EvictableRange) Overlaps(r2 EvictableRange) 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.
+//
+//go:nosplit
+func (r EvictableRange) IsSupersetOf(r2 EvictableRange) 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.
+//
+//go:nosplit
+func (r EvictableRange) Intersect(r2 EvictableRange) EvictableRange {
+	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.
+//
+//go:nosplit
+func (r EvictableRange) CanSplitAt(x uint64) bool {
+	return r.Contains(x) && r.Start < x
+}