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//
// AbstractCache.h
//
// $Id: //poco/1.4/Foundation/include/Poco/AbstractCache.h#1 $
//
// Library: Foundation
// Package: Cache
// Module: AbstractCache
//
// Definition of the AbstractCache class.
//
// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
#ifndef Foundation_AbstractCache_INCLUDED
#define Foundation_AbstractCache_INCLUDED
#include "Poco/KeyValueArgs.h"
#include "Poco/ValidArgs.h"
#include "Poco/Mutex.h"
#include "Poco/Exception.h"
#include "Poco/FIFOEvent.h"
#include "Poco/EventArgs.h"
#include "Poco/Delegate.h"
#include "Poco/SharedPtr.h"
#include <map>
#include <set>
#include <cstddef>
namespace Poco {
template <class TKey, class TValue, class TStrategy, class TMutex = FastMutex, class TEventMutex = FastMutex>
class AbstractCache
/// An AbstractCache is the interface of all caches.
{
public:
FIFOEvent<const KeyValueArgs<TKey, TValue >, TEventMutex > Add;
FIFOEvent<const KeyValueArgs<TKey, TValue >, TEventMutex > Update;
FIFOEvent<const TKey, TEventMutex> Remove;
FIFOEvent<const TKey, TEventMutex> Get;
FIFOEvent<const EventArgs, TEventMutex> Clear;
typedef std::map<TKey, SharedPtr<TValue > > DataHolder;
typedef typename DataHolder::iterator Iterator;
typedef typename DataHolder::const_iterator ConstIterator;
typedef std::set<TKey> KeySet;
AbstractCache()
{
initialize();
}
AbstractCache(const TStrategy& strat): _strategy(strat)
{
initialize();
}
virtual ~AbstractCache()
{
try
{
uninitialize();
}
catch (...)
{
poco_unexpected();
}
}
void add(const TKey& key, const TValue& val)
/// Adds the key value pair to the cache.
/// If for the key already an entry exists, it will be overwritten.
{
typename TMutex::ScopedLock lock(_mutex);
doAdd(key, val);
}
void update(const TKey& key, const TValue& val)
/// Adds the key value pair to the cache. Note that adding a NULL SharedPtr will fail!
/// If for the key already an entry exists, it will be overwritten.
/// The difference to add is that no remove or add events are thrown in this case,
/// just a simply silent update is performed
/// If the key does not exist the behavior is equal to add, ie. an add event is thrown
{
typename TMutex::ScopedLock lock(_mutex);
doUpdate(key, val);
}
void add(const TKey& key, SharedPtr<TValue > val)
/// Adds the key value pair to the cache. Note that adding a NULL SharedPtr will fail!
/// If for the key already an entry exists, it will be overwritten, ie. first a remove event
/// is thrown, then a add event
{
typename TMutex::ScopedLock lock(_mutex);
doAdd(key, val);
}
void update(const TKey& key, SharedPtr<TValue > val)
/// Adds the key value pair to the cache. Note that adding a NULL SharedPtr will fail!
/// If for the key already an entry exists, it will be overwritten.
/// The difference to add is that no remove or add events are thrown in this case,
/// just an Update is thrown
/// If the key does not exist the behavior is equal to add, ie. an add event is thrown
{
typename TMutex::ScopedLock lock(_mutex);
doUpdate(key, val);
}
void remove(const TKey& key)
/// Removes an entry from the cache. If the entry is not found,
/// the remove is ignored.
{
typename TMutex::ScopedLock lock(_mutex);
Iterator it = _data.find(key);
doRemove(it);
}
bool has(const TKey& key) const
/// Returns true if the cache contains a value for the key.
{
typename TMutex::ScopedLock lock(_mutex);
return doHas(key);
}
SharedPtr<TValue> get(const TKey& key)
/// Returns a SharedPtr of the value. The SharedPointer will remain valid
/// even when cache replacement removes the element.
/// If for the key no value exists, an empty SharedPtr is returned.
{
typename TMutex::ScopedLock lock(_mutex);
return doGet (key);
}
void clear()
/// Removes all elements from the cache.
{
typename TMutex::ScopedLock lock(_mutex);
doClear();
}
std::size_t size()
/// Returns the number of cached elements
{
typename TMutex::ScopedLock lock(_mutex);
doReplace();
return _data.size();
}
void forceReplace()
/// Forces cache replacement. Note that Poco's cache strategy use for efficiency reason no background thread
/// which periodically triggers cache replacement. Cache Replacement is only started when the cache is modified
/// from outside, i.e. add is called, or when a user tries to access an cache element via get.
/// In some cases, i.e. expire based caching where for a long time no access to the cache happens,
/// it might be desirable to be able to trigger cache replacement manually.
{
typename TMutex::ScopedLock lock(_mutex);
doReplace();
}
std::set<TKey> getAllKeys()
/// Returns a copy of all keys stored in the cache
{
typename TMutex::ScopedLock lock(_mutex);
doReplace();
ConstIterator it = _data.begin();
ConstIterator itEnd = _data.end();
std::set<TKey> result;
for (; it != itEnd; ++it)
result.insert(it->first);
return result;
}
protected:
mutable FIFOEvent<ValidArgs<TKey> > IsValid;
mutable FIFOEvent<KeySet> Replace;
void initialize()
/// Sets up event registration.
{
Add += Delegate<TStrategy, const KeyValueArgs<TKey, TValue> >(&_strategy, &TStrategy::onAdd);
Update += Delegate<TStrategy, const KeyValueArgs<TKey, TValue> >(&_strategy, &TStrategy::onUpdate);
Remove += Delegate<TStrategy, const TKey>(&_strategy, &TStrategy::onRemove);
Get += Delegate<TStrategy, const TKey>(&_strategy, &TStrategy::onGet);
Clear += Delegate<TStrategy, const EventArgs>(&_strategy, &TStrategy::onClear);
IsValid += Delegate<TStrategy, ValidArgs<TKey> >(&_strategy, &TStrategy::onIsValid);
Replace += Delegate<TStrategy, KeySet>(&_strategy, &TStrategy::onReplace);
}
void uninitialize()
/// Reverts event registration.
{
Add -= Delegate<TStrategy, const KeyValueArgs<TKey, TValue> >(&_strategy, &TStrategy::onAdd );
Update -= Delegate<TStrategy, const KeyValueArgs<TKey, TValue> >(&_strategy, &TStrategy::onUpdate);
Remove -= Delegate<TStrategy, const TKey>(&_strategy, &TStrategy::onRemove);
Get -= Delegate<TStrategy, const TKey>(&_strategy, &TStrategy::onGet);
Clear -= Delegate<TStrategy, const EventArgs>(&_strategy, &TStrategy::onClear);
IsValid -= Delegate<TStrategy, ValidArgs<TKey> >(&_strategy, &TStrategy::onIsValid);
Replace -= Delegate<TStrategy, KeySet>(&_strategy, &TStrategy::onReplace);
}
void doAdd(const TKey& key, const TValue& val)
/// Adds the key value pair to the cache.
/// If for the key already an entry exists, it will be overwritten.
{
Iterator it = _data.find(key);
doRemove(it);
KeyValueArgs<TKey, TValue> args(key, val);
Add.notify(this, args);
_data.insert(std::make_pair(key, SharedPtr<TValue>(new TValue(val))));
doReplace();
}
void doAdd(const TKey& key, SharedPtr<TValue>& val)
/// Adds the key value pair to the cache.
/// If for the key already an entry exists, it will be overwritten.
{
Iterator it = _data.find(key);
doRemove(it);
KeyValueArgs<TKey, TValue> args(key, *val);
Add.notify(this, args);
_data.insert(std::make_pair(key, val));
doReplace();
}
void doUpdate(const TKey& key, const TValue& val)
/// Adds the key value pair to the cache.
/// If for the key already an entry exists, it will be overwritten.
{
KeyValueArgs<TKey, TValue> args(key, val);
Iterator it = _data.find(key);
if (it == _data.end())
{
Add.notify(this, args);
_data.insert(std::make_pair(key, SharedPtr<TValue>(new TValue(val))));
}
else
{
Update.notify(this, args);
it->second = SharedPtr<TValue>(new TValue(val));
}
doReplace();
}
void doUpdate(const TKey& key, SharedPtr<TValue>& val)
/// Adds the key value pair to the cache.
/// If for the key already an entry exists, it will be overwritten.
{
KeyValueArgs<TKey, TValue> args(key, *val);
Iterator it = _data.find(key);
if (it == _data.end())
{
Add.notify(this, args);
_data.insert(std::make_pair(key, val));
}
else
{
Update.notify(this, args);
it->second = val;
}
doReplace();
}
void doRemove(Iterator it)
/// Removes an entry from the cache. If the entry is not found
/// the remove is ignored.
{
if (it != _data.end())
{
Remove.notify(this, it->first);
_data.erase(it);
}
}
bool doHas(const TKey& key) const
/// Returns true if the cache contains a value for the key
{
// ask the strategy if the key is valid
ConstIterator it = _data.find(key);
bool result = false;
if (it != _data.end())
{
ValidArgs<TKey> args(key);
IsValid.notify(this, args);
result = args.isValid();
}
return result;
}
SharedPtr<TValue> doGet(const TKey& key)
/// Returns a SharedPtr of the cache entry, returns 0 if for
/// the key no value was found
{
Iterator it = _data.find(key);
SharedPtr<TValue> result;
if (it != _data.end())
{
// inform all strategies that a read-access to an element happens
Get.notify(this, key);
// ask all strategies if the key is valid
ValidArgs<TKey> args(key);
IsValid.notify(this, args);
if (!args.isValid())
{
doRemove(it);
}
else
{
result = it->second;
}
}
return result;
}
void doClear()
{
static EventArgs _emptyArgs;
Clear.notify(this, _emptyArgs);
_data.clear();
}
void doReplace()
{
std::set<TKey> delMe;
Replace.notify(this, delMe);
// delMe contains the to be removed elements
typename std::set<TKey>::const_iterator it = delMe.begin();
typename std::set<TKey>::const_iterator endIt = delMe.end();
for (; it != endIt; ++it)
{
Iterator itH = _data.find(*it);
doRemove(itH);
}
}
TStrategy _strategy;
mutable DataHolder _data;
mutable TMutex _mutex;
private:
AbstractCache(const AbstractCache& aCache);
AbstractCache& operator = (const AbstractCache& aCache);
};
} // namespace Poco
#endif // Foundation_AbstractCache_INCLUDED
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