ceph/src/rocksdb/include/rocksdb/cleanable.h

   1 // Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 // This source code is licensed under the BSD-style license found in the
   3 // LICENSE file in the root directory of this source tree. An additional grant
   4 // of patent rights can be found in the PATENTS file in the same directory.
   5 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
   6 // Use of this source code is governed by a BSD-style license that can be
   7 // found in the LICENSE file. See the AUTHORS file for names of contributors.
   8 //
   9 // An iterator yields a sequence of key/value pairs from a source.
  10 // The following class defines the interface.  Multiple implementations
  11 // are provided by this library.  In particular, iterators are provided
  12 // to access the contents of a Table or a DB.
  13 //
  14 // Multiple threads can invoke const methods on an Iterator without
  15 // external synchronization, but if any of the threads may call a
  16 // non-const method, all threads accessing the same Iterator must use
  17 // external synchronization.
  18
  19 #ifndef INCLUDE_ROCKSDB_CLEANABLE_H_
  20 #define INCLUDE_ROCKSDB_CLEANABLE_H_
  21
  22 namespace rocksdb {
  23
  24 class Cleanable {
  25  public:
  26   Cleanable();
  27   ~Cleanable();
  28   // Clients are allowed to register function/arg1/arg2 triples that
  29   // will be invoked when this iterator is destroyed.
  30   //
  31   // Note that unlike all of the preceding methods, this method is
  32   // not abstract and therefore clients should not override it.
  33   typedef void (*CleanupFunction)(void* arg1, void* arg2);
  34   void RegisterCleanup(CleanupFunction function, void* arg1, void* arg2);
  35   void DelegateCleanupsTo(Cleanable* other);
  36   // DoCkeanup and also resets the pointers for reuse
  37   inline void Reset() {
  38     DoCleanup();
  39     cleanup_.function = nullptr;
  40     cleanup_.next = nullptr;
  41   }
  42
  43  protected:
  44   struct Cleanup {
  45     CleanupFunction function;
  46     void* arg1;
  47     void* arg2;
  48     Cleanup* next;
  49   };
  50   Cleanup cleanup_;
  51   // It also becomes the owner of c
  52   void RegisterCleanup(Cleanup* c);
  53
  54  private:
  55   // Performs all the cleanups. It does not reset the pointers. Making it
  56   // private
  57   // to prevent misuse
  58   inline void DoCleanup() {
  59     if (cleanup_.function != nullptr) {
  60       (*cleanup_.function)(cleanup_.arg1, cleanup_.arg2);
  61       for (Cleanup* c = cleanup_.next; c != nullptr;) {
  62         (*c->function)(c->arg1, c->arg2);
  63         Cleanup* next = c->next;
  64         delete c;
  65         c = next;
  66       }
  67     }
  68   }
  69 };
  70
  71 }  // namespace rocksdb
  72
  73 #endif  // INCLUDE_ROCKSDB_CLEANABLE_H_