int rehash()

in bytekit-core/src/main/java/com/alibaba/bytekit/utils/concurrent/ConcurrentWeakKeyHashMap.java [496:559]
43 lines of code
9 McCabe index (conditional complexity)

        int rehash() {
            HashEntry<K, V>[] oldTable = table;
            int oldCapacity = oldTable.length;
            if (oldCapacity >= MAXIMUM_CAPACITY) {
                return 0;
            }

            /*
             * Reclassify nodes in each list to new Map.  Because we are using
             * power-of-two expansion, the elements from each bin must either
             * stay at same index, or move with a power of two offset. We
             * eliminate unnecessary node creation by catching cases where old
             * nodes can be reused because their next fields won't change.
             * Statistically, at the default threshold, only about one-sixth of
             * them need cloning when a table doubles. The nodes they replace
             * will be garbage collectable as soon as they are no longer
             * referenced by any reader thread that may be in the midst of
             * traversing table right now.
             */

            HashEntry<K, V>[] newTable = HashEntry.newArray(oldCapacity << 1);
            threshold = (int) (newTable.length * loadFactor);
            int sizeMask = newTable.length - 1;
            int reduce = 0;
            for (HashEntry<K, V> e: oldTable) {
                // We need to guarantee that any existing reads of old Map can
                // proceed. So we cannot yet null out each bin.
                if (e != null) {
                    HashEntry<K, V> next = e.next;
                    int idx = e.hash & sizeMask;

                    // Single node on list
                    if (next == null) {
                        newTable[idx] = e;
                    } else {
                        // Reuse trailing consecutive sequence at same slot
                        HashEntry<K, V> lastRun = e;
                        int lastIdx = idx;
                        for (HashEntry<K, V> last = next; last != null; last = last.next) {
                            int k = last.hash & sizeMask;
                            if (k != lastIdx) {
                                lastIdx = k;
                                lastRun = last;
                            }
                        }
                        newTable[lastIdx] = lastRun;
                        // Clone all remaining nodes
                        for (HashEntry<K, V> p = e; p != lastRun; p = p.next) {
                            // Skip GC'd weak references
                            K key = p.key();
                            if (key == null) {
                                reduce++;
                                continue;
                            }
                            int k = p.hash & sizeMask;
                            HashEntry<K, V> n = newTable[k];
                            newTable[k] = newHashEntry(key, p.hash, n, p.value());
                        }
                    }
                }
            }
            table = newTable;
            return reduce;
        }