vtkStringManager.h

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// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-License-Identifier: BSD-3-Clause
#ifndef vtkStringManager_h
#define vtkStringManager_h
#include "vtkObject.h"
#include "vtkStringToken.h" // for vtkStringToken::Hash type-alias.
 
#include <functional>
#include <mutex>
#include <unordered_map>
#include <unordered_set>
 
VTK_ABI_NAMESPACE_BEGIN
 
class VTKCOMMONCORE_EXPORT vtkStringManager : public vtkObject
{
public:
  vtkTypeMacro(vtkStringManager, vtkObject);
  static vtkStringManager* New();
  void PrintSelf(ostream& os, vtkIndent indent) override;
 
  enum Visit
  {
    Halt,    
    Continue 
  };
 
  using Hash = std::uint32_t;
 
  using Visitor = std::function<Visit(Hash entry)>;
  static constexpr Hash Invalid = 0;
 
  Hash Manage(const std::string& ss);
  std::size_t Unmanage(Hash hh);
 
  const std::string& Value(Hash hh) const;
  Hash Find(const std::string& s) const;
  Hash Compute(const std::string& ss) const;
 
  Hash Insert(const std::string& ss, Hash hh);
  bool Insert(Hash ss, Hash hh);
  bool Remove(const std::string& ss, Hash hh);
  bool Remove(Hash ss, Hash hh);
 
  bool Contains(const std::string& ss, Hash hh) const;
  bool Contains(Hash ss, Hash hh) const;
  bool Contains(Hash hh) const { return this->Contains(Invalid, hh); }
 
  bool Empty() const { return this->Data.empty(); }
 
  Visit VisitMembers(Visitor visitor, Hash set = Invalid) const;
 
  Visit VisitSets(Visitor visitor) const;
 
  void Reset();
 
protected:
  vtkStringManager() = default;
 
private:
  using LockGuard = std::lock_guard<std::mutex>;
  std::pair<Hash, bool> ComputeInternal(const std::string& s, const LockGuard& proofOfLock) const;
  std::pair<Hash, bool> ComputeInternalAndInsert(
    const std::string& s, const LockGuard& proofOfLock);
  std::size_t UnmanageInternal(Hash hh, const LockGuard& proofOfLock);
 
  std::unordered_map<Hash, std::string> Data;
  std::unordered_map<Hash, std::unordered_set<Hash>> Sets;
  mutable std::mutex WriteLock;
 
  vtkStringManager(const vtkStringManager&) = delete;
  void operator=(const vtkStringManager&) = delete;
};
 
VTK_ABI_NAMESPACE_END
#endif // vtkStringManager_h