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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
// An iterator yields a sequence of key/value pairs from a source.
// The following class defines the interface. Multiple implementations
// are provided by this library. In particular, iterators are provided
// to access the contents of a Table or a DB.
// Multiple threads can invoke const methods on an Iterator without
// external synchronization, but if any of the threads may call a
// non-const method, all threads accessing the same Iterator must use
// external synchronization.
namespace rocksdb {
class Cleanable {
// No copy constructor and copy assignment allowed.
Cleanable(Cleanable&) = delete;
Cleanable& operator=(Cleanable&) = delete;
// Move consturctor and move assignment is allowed.
Cleanable& operator=(Cleanable&&);
// Clients are allowed to register function/arg1/arg2 triples that
// will be invoked when this iterator is destroyed.
// Note that unlike all of the preceding methods, this method is
// not abstract and therefore clients should not override it.
typedef void (*CleanupFunction)(void* arg1, void* arg2);
void RegisterCleanup(CleanupFunction function, void* arg1, void* arg2);
void DelegateCleanupsTo(Cleanable* other);
// DoCleanup and also resets the pointers for reuse
inline void Reset() {
cleanup_.function = nullptr; = nullptr;
struct Cleanup {
CleanupFunction function;
void* arg1;
void* arg2;
Cleanup* next;
Cleanup cleanup_;
// It also becomes the owner of c
void RegisterCleanup(Cleanup* c);
// Performs all the cleanups. It does not reset the pointers. Making it
// private
// to prevent misuse
inline void DoCleanup() {
if (cleanup_.function != nullptr) {
(*cleanup_.function)(cleanup_.arg1, cleanup_.arg2);
for (Cleanup* c =; c != nullptr;) {
(*c->function)(c->arg1, c->arg2);
Cleanup* next = c->next;
delete c;
c = next;
} // namespace rocksdb