1 files changed, 36 insertions, 0 deletions
diff --git a/src/internal/runtime/maps/export_test.go b/src/internal/runtime/maps/export_test.go
index 369ef1f2fe..8f62739665 100644
--- a/src/internal/runtime/maps/export_test.go
+++ b/src/internal/runtime/maps/export_test.go
@@ -36,12 +36,48 @@ func (m *Map) GroupCount() uint64 {
 	return n
 }
 
+// Return a key from a group containing no empty slots, or nil if there are no
+// full groups.
+//
+// Also returns nil if a group is full but contains entirely deleted slots.
+func (m *Map) KeyFromFullGroup() unsafe.Pointer {
+	var lastTab *table
+	for _, t := range m.directory {
+		if t == lastTab {
+			continue
+		}
+		lastTab = t
+
+		for i := uint64(0); i <= t.groups.lengthMask; i++ {
+			g := t.groups.group(i)
+			match := g.ctrls().matchEmpty()
+			if match != 0 {
+				continue
+			}
+
+			// All full or deleted slots.
+			for j := uint32(0); j < abi.SwissMapGroupSlots; j++ {
+				if g.ctrls().get(j) == ctrlDeleted {
+					continue
+				}
+				return g.key(j)
+			}
+		}
+	}
+
+	return nil
+}
+
 func (m *Map) TableFor(key unsafe.Pointer) *table {
 	hash := m.typ.Hasher(key, m.seed)
 	idx := m.directoryIndex(hash)
 	return m.directory[idx]
 }
 
+func (t *table) GrowthLeft() uint64 {
+	return uint64(t.growthLeft)
+}
+
 // Returns the start address of the groups array.
 func (t *table) GroupsStart() unsafe.Pointer {
 	return t.groups.data