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109 lines
3.5 KiB
C++
109 lines
3.5 KiB
C++
/* Icinga 2 | (c) 2012 Icinga GmbH | GPLv2+ */
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#ifndef NAMESPACE_H
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#define NAMESPACE_H
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#include "base/i2-base.hpp"
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#include "base/object.hpp"
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#include "base/objectlock.hpp"
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#include "base/shared-object.hpp"
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#include "base/value.hpp"
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#include "base/debuginfo.hpp"
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#include <atomic>
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#include <map>
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#include <vector>
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#include <memory>
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#include <shared_mutex>
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namespace icinga
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{
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struct NamespaceValue
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{
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Value Val;
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bool Const;
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};
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/**
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* A namespace.
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*
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* ## External Locking
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*
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* Synchronization is handled internally, so almost all functions are safe for concurrent use without external locking.
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* The only exception to this are functions returning an iterator. To use these, the caller has to acquire an ObjectLock
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* on the namespace. The iterators only remain valid for as long as that ObjectLock is held. Note that this also
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* includes range-based for loops.
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*
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* If consistency across multiple operations is required, an ObjectLock must also be acquired to prevent concurrent
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* modifications.
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*
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* ## Internal Locking
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*
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* Two mutex objects are involved in locking a namespace: the recursive mutex inherited from the Object class that is
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* acquired and released using the ObjectLock class and the m_DataMutex shared mutex contained directly in the
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* Namespace class. The ObjectLock is used to synchronize multiple write operations against each other. The shared mutex
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* is only used to ensure the consistency of the m_Data data structure.
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*
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* Read operations must acquire a shared lock on m_DataMutex. This prevents concurrent writes to that data structure
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* but still allows concurrent reads.
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*
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* Write operations must first obtain an ObjectLock and then a shared lock on m_DataMutex. This order is important for
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* preventing deadlocks. The ObjectLock prevents concurrent write operations while the shared lock prevents concurrent
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* read operations.
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*
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* External read access to iterators is synchronized by the caller holding an ObjectLock. This ensures no concurrent
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* write operations as these require the ObjectLock but still allows concurrent reads as m_DataMutex is not locked.
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*
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* @ingroup base
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*/
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class Namespace final : public Object
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{
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public:
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DECLARE_OBJECT(Namespace);
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typedef std::map<String, NamespaceValue>::iterator Iterator;
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typedef std::map<String, NamespaceValue>::value_type Pair;
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explicit Namespace(bool constValues = false);
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Value Get(const String& field) const;
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bool Get(const String& field, Value *value) const;
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void Set(const String& field, const Value& value, bool isConst = false, const DebugInfo& debugInfo = DebugInfo());
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bool Contains(const String& field) const;
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void Remove(const String& field);
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void Freeze();
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bool Frozen() const;
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ObjectLock LockIfRequired();
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Iterator Begin();
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Iterator End();
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size_t GetLength() const;
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Value GetFieldByName(const String& field, bool sandboxed, const DebugInfo& debugInfo) const override;
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void SetFieldByName(const String& field, const Value& value, const DebugInfo& debugInfo) override;
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bool HasOwnField(const String& field) const override;
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bool GetOwnField(const String& field, Value *result) const override;
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static Object::Ptr GetPrototype();
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private:
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std::shared_lock<std::shared_timed_mutex> ReadLockUnlessFrozen() const;
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std::map<String, NamespaceValue> m_Data;
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mutable std::shared_timed_mutex m_DataMutex;
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bool m_ConstValues;
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std::atomic<bool> m_Frozen;
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};
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Namespace::Iterator begin(const Namespace::Ptr& x);
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Namespace::Iterator end(const Namespace::Ptr& x);
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}
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extern template class std::map<icinga::String, std::shared_ptr<icinga::NamespaceValue> >;
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#endif /* NAMESPACE_H */
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