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