SharedCluster.h

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//===------------------SharedCluster.h --------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#ifndef LLDB_UTILITY_SHAREDCLUSTER_H
#define LLDB_UTILITY_SHAREDCLUSTER_H
 
#include "lldb/Utility/LLDBAssert.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
 
#include <memory>
#include <mutex>
 
namespace lldb_private {
 
template <class T>
class ClusterManager : public std::enable_shared_from_this<ClusterManager<T>> {
public:
  static std::shared_ptr<ClusterManager> Create() {
    return std::shared_ptr<ClusterManager>(new ClusterManager());
  }
 
  ~ClusterManager() {
    for (T *obj : m_objects)
      delete obj;
  }
 
  void ManageObject(T *new_object) {
    std::lock_guard<std::mutex> guard(m_mutex);
    auto ret = m_objects.insert(new_object);
    assert(ret.second && "ManageObject called twice for the same object?");
    (void)ret;
  }
 
  std::shared_ptr<T> GetSharedPointer(T *desired_object) {
    std::lock_guard<std::mutex> guard(m_mutex);
    auto this_sp = this->shared_from_this();
    size_t count =  m_objects.count(desired_object);
    if (count == 0) {
      lldbassert(false && "object not found in shared cluster when expected");
      desired_object = nullptr;
    }
    return {std::move(this_sp), desired_object};
  }
 
private:
  ClusterManager() : m_objects() {}
  // The cluster manager is used primarily to manage the
  // children of root ValueObjects. So it will always have
  // one element - the root.  Pointers will often have dynamic
  // values, so having 2 entries is pretty common.  It's also
  // pretty common to have small (2,3) structs, so setting the
  // static size to 4 will cover those cases with no allocations
  // w/o wasting too much space.
  llvm::SmallPtrSet<T *, 4> m_objects;
  std::mutex m_mutex;
};
 
} // namespace lldb_private
 
#endif // LLDB_UTILITY_SHAREDCLUSTER_H