Add SingleMap_Leapfrog

[junction.git] / junction / ConcurrentMap_Leapfrog.h

diff --git a/junction/ConcurrentMap_Leapfrog.h b/junction/ConcurrentMap_Leapfrog.h
index 89ba120d435ff0738291a8318364eb9a0165de67..3a8493e62d18ec979cc4f2d26038d470cb0814f3 100644 (file)
--- a/junction/ConcurrentMap_Leapfrog.h
+++ b/junction/ConcurrentMap_Leapfrog.h
@@ -114,6 +114,12 @@ public:
                     return; // Found an existing value
                 }
                 case Details::InsertResult_Overflow: {
                     return; // Found an existing value
                 }
                 case Details::InsertResult_Overflow: {

+                    // Unlike ConcurrentMap_Linear, we don't need to keep track of & pass a "mustDouble" flag.
+                    // Passing overflowIdx is sufficient to prevent an infinite loop here.
+                    // It defines the start of the range of cells to check while estimating total cells in use.
+                    // After the first migration, deleted keys are purged, so if we hit this line during the
+                    // second loop iteration, every cell in the range will be in use, thus the estimate will be 100%.
+                    // (Concurrent deletes could result in further iterations, but it will eventually settle.)

                     Details::beginTableMigration(m_map, m_table, overflowIdx);
                     break;
                 }
                     Details::beginTableMigration(m_map, m_table, overflowIdx);
                     break;
                 }